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Table Of Contents
Cisco NSF Routing and Forwarding Operation
Related Features and Technologies
Supported Standards, MIBs, and RFCs
Configuring BGP NSF Neighbor Device Example
Cisco Nonstop Forwarding
Feature History
This document describes the Cisco Nonstop Forwarding (NSF) feature in Cisco IOS Release 12.0(24)S. It includes the following sections:
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Supported Standards, MIBs, and RFCs
Note
Feature Overview
Cisco NSF works with the Stateful Switchover (SSO) feature in Cisco IOS software. SSO is a prerequisite of Cisco NSF. NSF works with SSO to minimize the amount of time a network is unavailable to its users following a switchover. The main objective of Cisco NSF is to continue forwarding IP packets following a route processor (RP) switchover.
Usually, when a networking device restarts, all routing peers of that device detect that the device went down and then came back up. This transition results in what is called a routing flap, which could spread across multiple routing domains. Routing flaps caused by routing restarts create routing instabilities, which are detrimental to the overall network performance. Cisco NSF helps to suppress routing flaps in SSO-enabled devices, thus reducing network instability.
Cisco NSF allows for the forwarding of data packets to continue along known routes while the routing protocol information is being restored following a switchover. With Cisco NSF, peer networking devices do not experience routing flaps. Data traffic is forwarded through intelligent line cards or dual forwarding processors (FPs) while the standby RP assumes control from the failed active RP during a switchover. The ability of line cards and FPs to remain up through a switchover and to be kept current with the Forwarding Information Base (FIB) on the active RP is key to Cisco NSF operation.
SSO Dependency
Cisco NSF always runs together with SSO. This section provides some background information on the SSO feature.
In specific Cisco networking devices that support dual RPs, SSO establishes one of the RPs as the active processor while the other RP is designated as the standby processor, and then synchronizes information between them. A switchover from the active to the standby processor occurs when the active RP fails, is removed from the networking device, or is manually taken down for maintenance.
In networking devices running SSO, both RPs must be running the same configuration so that the standby RP is always ready to assume control following a fault on the active RP. The configuration information is synchronized from the active RP to the standby RP at startup and whenever changes to the active RP configuration occur. Following an initial synchronization between the two processors, SSO maintains RP state information between them, including forwarding information.
During switchover, system control and routing protocol execution is transferred from the active processor to the standby processor. The time required by the device to switch over from the active to the standby processor ranges from just a few seconds to approximately 30 seconds, depending on the platform.
SSO supported protocols and applications must be high-availability (HA)-aware. A feature or protocol is HA aware if it maintains, either partially or completely, undisturbed operation through an RP switchover. For some HA aware protocols and applications, state information is synchronized from the active to the standby processor. For Cisco NSF, enhancements to the routing protocols (Cisco Express Forwarding, or CEF; Open Shortest Path First, or OSPF; Border Gateway Protocol, or BGP; and Intermediate System-to-Intermediate System, or IS-IS) have been made to support the HA features in SSO.
For more information on SSO, see the section "Related Documents."
Cisco NSF Routing and Forwarding Operation
Cisco NSF is supported by the BGP, OSPF, and IS-IS protocols for routing and by Cisco Express Forwarding (CEF) for forwarding. Of the routing protocols, BGP, OSPF, and IS-IS have been enhanced with NSF-capability and awareness, which means that routers running these protocols can detect a switchover and take the necessary actions to continue forwarding network traffic and to recover route information from the peer devices. The IS-IS protocol can be configured to use state information that has been synchronized between the active and the standby RP to recover route information following a switchover instead of information received from peer devices.
In this document, a networking device is said to be NSF-aware if it is running NSF-compatible software. A device is said to be NSF-capable if it has been configured to support NSF; therefore, it would rebuild routing information from NSF-aware or NSF-capable neighbors.
Each protocol depends on CEF to continue forwarding packets during switchover while the routing protocols rebuild the Routing Information Base (RIB) tables. Once the routing protocols have converged, CEF updates the FIB table and removes stale route entries. CEF, in turn, updates the line cards with the new FIB information.
Table 1 lists the routing protocol and CEF support in Cisco NSF.
Table 1 Routing Protocol and CEF Support in Cisco NSF
BGP
Cisco 7200
Yes1
Yes1
Yes1
Cisco 7500
Yes
Yes
Yes
Cisco 10000
Yes
Yes
Yes
Cisco 12000
Yes
Yes
Yes
OSPF
Cisco 7200
Yes1
Yes1
Yes1
Cisco 7500
Yes
Yes
Yes
Cisco 10000
Yes
Yes
Yes
Cisco 12000
Yes
Yes
Yes
IS-IS
Cisco 7200
Yes1
Yes
Yes1
Cisco 7500
Yes
Yes
Yes
Cisco 10000
Yes
Yes
Yes
Cisco 12000
Yes
Yes
Yes
CEF
Cisco 7200
N/A2
N/A2
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Cisco 7500
Yes
Yes
Yes
Cisco 10000
Yes
Yes
Yes
Cisco 12000
Yes
Yes
Yes
1 The Cisco 7200 is a single-route processor system and cannot maintain its forwarding table in the event of a route processor failure. It cannot perform nonstop forwarding of packets. However, it supports the NSF protocol extensions for BGP, OSPF, and ISIS. Therefore, it can peer with NSF-capable routers and facilitate the resynchronization of routing information with such routers.
2 The Cisco 7200 is a single processor device and does not support SSO; therefore, CEF support for NSF does not apply.
Cisco Express Forwarding
A key element of NSF is packet forwarding. In a Cisco networking device, packet forwarding is provided by CEF. CEF maintains the FIB, and uses the FIB information that was current at the time of the switchover to continue forwarding packets during a switchover. This feature reduces traffic interruption during the switchover.
During normal NSF operation, CEF on the active RP synchronizes its current FIB and adjacency databases with the FIB and adjacency databases on the standby RP. Upon switchover of the active RP, the standby RP initially has FIB and adjacency databases that are mirror images of those that were current on the active RP. For platforms with intelligent line cards, the line cards will maintain the current forwarding information over a switchover; for platforms with forwarding engines, CEF will keep the forwarding engine on the standby RP current with changes that are sent to it by CEF on the active RP. In this way, the line cards or forwarding engines will be able to continue forwarding after a switchover as soon as the interfaces and a data path are available.
As the routing protocols start to repopulate the RIB on a prefix-by-prefix basis, the updates in turn cause prefix-by-prefix updates to CEF, which it uses to update the FIB and adjacency databases. Existing and new entries will receive the new version ("epoch") number, indicating that they have been refreshed. The forwarding information is updated on the line cards or forwarding engine during convergence. The RP signals when the RIB has converged. The software removes all FIB and adjacency entries that have an epoch older than the current switchover epoch. The FIB now represents the newest routing protocol forwarding information.
Routing Protocols
The routing protocols run only on the active RP, and they receive routing updates from their neighbor routers. Routing protocols do not run on the standby RP. Following a switchover, the routing protocols request that the NSF-aware neighbor devices send state information to help rebuild the routing tables. Alternately, the IS-IS protocol can be configured to synchronize state information from the active to the standby RP to help rebuild the routing table on the NSF-capable device in environments where neighbor devices are not NSF-aware.
Note
BGP Operation
When a NSF-capable router begins a BGP session with a BGP peer, it sends an OPEN message to the peer. Included in the message is a declaration that the NSF-capable device has "graceful restart capability." Graceful restart is the mechanism by which BGP routing peers avoid a routing flap following a switchover. If the BGP peer has received this capability, it is aware that the device sending the message is NSF-capable. Both the NSF-capable router and its BGP peer(s) need to exchange the Graceful Restart Capability in their OPEN messages, at the time of session establishment. If both the peers do not exchange the Graceful Restart Capability, the session will not be graceful restart capable.
If the BGP session is lost during the RP switchover, the NSF-aware BGP peer marks all the routes associated with the NSF-capable router as stale; however, it continues to use these routes to make forwarding decisions for a set period of time. This functionality means that no packets are lost while the newly active RP is waiting for convergence of the routing information with the BGP peers.
After an RP switchover occurs, the NSF-capable router reestablishes the session with the BGP peer. In establishing the new session, it sends a new graceful restart message that identifies the NSF-capable router as having restarted.
At this point, the routing information is exchanged between the two BGP peers. Once this exchange is complete, the NSF-capable device uses the routing information to update the RIB and the FIB with the new forwarding information. The NSF-aware device uses the network information to remove stale routes from its BGP table. Following that, the BGP protocol is fully converged.
If a BGP peer does not support the graceful restart capability, it will ignore the graceful-restart capability in an OPEN message but will establish a BGP session with the NSF-capable device. This function will allow interoperability with non-NSF-aware BGP peers (and without NSF functionality), but the BGP session with non-NSF-aware BGP peers will not be graceful restart capable.
Note
OSPF Operation
When an OSPF NSF-capable router performs an RP switchover, it must perform two tasks in order to resynchronize its Link State Database with its OSPF neighbors. First, it must relearn the available OSPF neighbors on the network without causing a reset of the neighbor relationship. Second, it must reacquire the contents of the Link State Database for the network.
As quickly as possible after an RP switchover, the NSF-capable router sends an OSPF NSF signal to neighboring NSF-aware devices. Neighbor networking devices recognize this signal as a cue that the neighbor relationship with this router should not be reset. As the NSF-capable router receives signals from other routers on the network, it can begin to rebuild its neighbor list.
Once neighbor relationships are reestablished, the NSF-capable router begins to resynchronize its database with all of its NSF-aware neighbors. At this point, the routing information is exchanged between the OSPF neighbors. Once this exchange is complete, the NSF-capable device uses the routing information to remove stale routes, update the RIB, and update the FIB with the new forwarding information. The OSPF protocols are then fully converged.
Note
IS-IS Operation
When an IS-IS NSF-capable router performs an RP switchover, it must perform two tasks in order to resynchronize its Link State Database with its IS-IS neighbors. First, it must relearn the available IS-IS neighbors on the network without causing a reset of the neighbor relationship. Second, it must reacquire the contents of the Link State Database for the network.
The IS-IS NSF feature offers two options when configuring NSF:
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If neighbor routers on a network segment are NSF-aware, meaning that neighbor routers are running a software version that supports the IETF Internet draft for router restartability, they will assist an IETF NSF router which is restarting. With IETF, neighbor routers provide adjacency and link-state information to help rebuild the routing information following a switchover. A benefit of IETF IS-IS configuration is operation between peer devices based on a proposed standard.
Note
If the neighbor routers on a network segment are not NSF-aware, you must use the Cisco configuration option. The Cisco IS-IS configuration transfers both protocol adjacency and link-state information from the active to the standby RP. A benefit of Cisco configuration is that it does not rely on NSF-aware neighbors.
IETF IS-IS Configuration
Using the IETF IS-IS configuration, as quickly as possible after an RP switchover, the NSF-capable router sends IS-IS NSF restart requests to neighboring NSF-aware devices. Neighbor networking devices recognize this restart request as a cue that the neighbor relationship with this router should not be reset, but that they should initiate database resynchronization with the restarting router. As the restarting router receives restart request responses from routers on the network, it can begin to rebuild its neighbor list.
Once this exchange is complete, the NSF-capable device uses the link-state information to remove stale routes, update the RIB, and update the FIB with the new forwarding information. IS-IS is then fully converged.
The switchover from one RP to the other happens within seconds. IS-IS reestablishes its routing table and resynchronizes with the network within a few additional seconds. At this point, IS-IS waits for a specified interval before it will attempt a second NSF restart. During this time, the new standby RP will boot up and synchronize its configuration with the active RP. The IS-IS NSF operation waits for a specified interval to ensure that connections are stable before attempting another restart of IS-IS NSF. This functionality prevents IS-IS from attempting back-to-back NSF restarts with stale information.
Cisco IS-IS Configuration
Using the Cisco configuration option, full adjacency and LSP information is saved, or "checkpointed," to the standby RP. Following a switchover, the newly active RP maintains its adjacencies using the checkpointed data, and can quickly rebuild its routing tables.
Note
The switchover from one RP to the other happens within seconds. IS-IS reestablishes its routing table and resynchronizes with the network within a few additional seconds. At this point, IS-IS waits for a specified interval before it will attempt a second NSF restart. During this time, the new standby RP will boot up and synchronize its configuration with the active RP. Once this synchronization is completed, IS-IS adjacency and LSP data is checkpointed to the standby RP; however, a new NSF restart will not be attempted by IS-IS until the interval time expires. This functionality prevents IS-IS from attempting back-to-back NSF restarts.
Benefits
Improved Network Availability
NSF continues forwarding network traffic and application state information so that user session information is maintained after a switchover.
Overall Network Stability
Network stability may be improved with the reduction in the number of route flaps that had been created when routers in the network failed and lost their routing tables.
Neighboring Routers Do Not Detect a Link Flap
Because the interfaces remain up across a switchover, neighboring routers do not detect a link flap (the link does not go down and come back up).
Prevents Routing Flaps
Because SSO continues forwarding network traffic in the event of a switchover, routing flaps are avoided.
No Loss of User Sessions
User sessions established prior to the switchover are maintained.
Restrictions
General Restrictions
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BGP NSF
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OSPF NSF
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IS-IS NSF
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Cisco 7200 Series Router
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The Cisco 7206 does support NSF and can operate in a peer role with a Cisco 7500, 10000, or 12000 series router running Cisco IOS Release 12.0(23)S. With NSF enabled, an RP switchover on the Cisco 7500, 10000, or 12000 series router peer should not cause a loss of PPP, ATM, high-level data link control (HDLC), or Frame Relay sessions, or a loss of any OSPF, BGP, or IS-IS adjacencies established between the Cisco 7200 and the peer.
Related Features and Technologies
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Related Documents
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Supported Platforms
Determining Platform Support Through Cisco Feature Navigator
Cisco IOS software is packaged in feature sets that are supported on specific platforms. To obtain updated information about platform support for this feature, access Cisco Feature Navigator. Cisco Feature Navigator dynamically updates the list of supported platforms as new platform support is added for the feature.
Cisco Feature Navigator is a web-based tool that enables you to determine which Cisco IOS software images support a specific set of features and which features are supported in a specific Cisco IOS image. You can search by feature or release. In the release section, you can compare releases side by side to display both the features unique to each software release and the features that releases have in common.
To access Cisco Feature Navigator, you must have an account on Cisco.com. If you have forgotten or lost your account information, send a blank e-mail to cco-locksmith@cisco.com. An automatic check will verify that your e-mail address is registered with Cisco.com. If the check is successful, account details with a new random password will be e-mailed to you. Qualified users can establish an account on Cisco.com by following the directions at http://www.cisco.com/register.
Cisco Feature Navigator is updated regularly when major Cisco IOS software releases and technology releases occur. For the most current information, go to the Cisco Feature Navigator home page at the following URL:
Availability of Cisco IOS Software Images
Platform support for particular Cisco IOS software releases is dependent on the availability of the software images for those platforms. Software images for some platforms may be deferred, delayed, or changed without prior notice. For updated information about platform support and availability of software images for each Cisco IOS software release, refer to the online release notes or, if supported, Cisco Feature Navigator.
Supported Standards, MIBs, and RFCs
Standards
Restart Signaling for ISIS, Internet Engineering Task Force (IETF) Network Working Group Internet Draft, September 2001
MIBs
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To obtain lists of supported MIBs by platform and Cisco IOS release, and to download MIB modules, go to the Cisco MIB website on Cisco.com at the following URL:
http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml
RFCs
No new or modified RFCs are supported by this feature.
Prerequisites
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Configuration Tasks
See the following sections for configuration tasks for the SSO feature. Each task in the list is identified as either required or optional.
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Configuring CEF NSF
The CEF NSF feature operates by default while the networking device is running in SSO mode. No configuration is necessary.
Configuring BGP NSF
Note
To configure BGP for NSF, use the following commands beginning in privileged EXEC mode, and repeat this procedure on each of the BGP NSF peer devices:
Configuring OSPF NSF
Note
To configure NSF for OSPF, use the following commands beginning in privileged EXEC mode:
Configuring IS-IS NSF
To configure NSF for IS-IS, use the following commands beginning in privileged EXEC mode:
Verifying CEF NSF
To verify that CEF is NSF-capable, use the show cef state command:
router# show cef stateCEF Status [RP]CEF enabled/runningdCEF enabled/runningCEF switching enabled/runningCEF default capabilities:Always FIB switching: yesDefault CEF switching: yesDefault dCEF switching: yesUpdate HWIDB counters: noDrop multicast packets: no...CEF NSF capable: yesIPC delayed func on SSO: noRRP state:I am standby RRP: noMy logical slot: 0RF PeerComm: noVerifying BGP NSF
To verify NSF for BGP, you must check that the graceful restart function is configured on the SSO-enabled networking device and on the neighbor devices. Perform the following steps:
Step 1
Router# show running-config...router bgp 120...bgp graceful-restartneighbor 10.2.2.2 remote-as 300...
Step 2
Step 3
router#show ip bgp neighbors x.x.x.xBGP neighbor is 192.168.2.2, remote AS YY, external linkBGP version 4, remote router ID 192.168.2.2BGP state = Established, up for 00:01:18Last read 00:00:17, hold time is 180, keepalive interval is 60 secondsNeighbor capabilities:Route refresh:advertised and received(new)Address family IPv4 Unicast:advertised and receivedAddress famiiy IPv4 Multicast:advertised and receivedGraceful Restart Capabilty:advertised and receivedRemote Restart timer is 120 secondsAddress families preserved by peer:IPv4 Unicast, IPv4 MulticastReceived 1539 messages, 0 notifications, 0 in queueSent 1544 messages, 0 notifications, 0 in queueDefault minimum time between advertisement runs is 30 seconds
Verifying OSPF NSF
To verify NSF for OSPF, you must check that the NSF function is configured on the SSO-enabled networking device. Perform the following steps:
Step 1
Router# show running-configrouter ospf 120log-adjacency-changesnsfnetwork 192.168.20.0 0.0.0.255 area 0network 192.168.30.0 0.0.0.255 area 1network 192.168.40.0 0.0.0.255 area 2...Step 2
router> show ip ospfRouting Process "ospf 1" with ID 192.168.2.1 and Domain ID 0.0.0.1Supports only single TOS(TOS0) routesSupports opaque LSASPF schedule delay 5 secs, Hold time between two SPFs 10 secsMinimum LSA interval 5 secs. Minimum LSA arrival 1 secsNumber of external LSA 0. Checksum Sum 0x0Number of opaque AS LSA 0. Checksum Sum 0x0Number of DCbitless external and opaque AS LSA 0Number of DoNotAge external and opaque AS LSA 0Number of areas in this router is 1. 1 normal 0 stub 0 nssaExternal flood list length 0Non-Stop Forwarding enabled, last NSF restart 00:02:06 ago (took 44 secs)Area BACKBONE(0)Number of interfaces in this area is 1 (0 loopback)Area has no authenticationSPF algorithm executed 3 timesVerifying IS-IS NSF
To verify NSF for IS-IS, you must check that the NSF function is configured on the SSO-enabled networking device. Perform the following steps:
Step 1
Router# show running-config...router isisnsf cisco...Step 2
router# show isis nsfNSF is ENABLED, mode 'cisco'RP is ACTIVE, standby ready, bulk sync completeNSF interval timer expired (NSF restart enabled)Checkpointing enabled, no errorsLocal state:ACTIVE, Peer state:STANDBY HOT, Mode:SSOThe following display shows sample output for the Cisco configuration on the standby RP. In this example, note the presence of "NSF restart enabled":
router# show isis nsfNSF enabled, mode 'cisco'RP is STANDBY, chkpt msg receive count:ADJ 2, LSP 7NSF interval timer notification received (NSF restart enabled)Checkpointing enabled, no errorsLocal state:STANDBY HOT, Peer state:ACTIVE, Mode:SSOStep 3
router# show isis nsfNSF is ENABLED, mode IETFNSF pdb state:InactiveNSF L1 active interfaces:0NSF L1 active LSPs:0NSF interfaces awaiting L1 CSNP:0Awaiting L1 LSPs:NSF L2 active interfaces:0NSF L2 active LSPs:0NSF interfaces awaiting L2 CSNP:0Awaiting L2 LSPs:Interface:Serial3/0/2NSF L1 Restart state:RunningNSF p2p Restart retransmissions:0Maximum L1 NSF Restart retransmissions:3L1 NSF ACK requested:FALSEL1 NSF CSNP requested:FALSENSF L2 Restart state:RunningNSF p2p Restart retransmissions:0Maximum L2 NSF Restart retransmissions:3L2 NSF ACK requested:FALSEInterface:GigabitEthernet2/0/0NSF L1 Restart state:RunningNSF L1 Restart retransmissions:0Maximum L1 NSF Restart retransmissions:3L1 NSF ACK requested:FALSEL1 NSF CSNP requested:FALSENSF L2 Restart state:RunningNSF L2 Restart retransmissions:0Maximum L2 NSF Restart retransmissions:3L2 NSF ACK requested:FALSEL2 NSF CSNP requested:FALSEInterface:Loopback1NSF L1 Restart state:RunningNSF L1 Restart retransmissions:0Maximum L1 NSF Restart retransmissions:3L1 NSF ACK requested:FALSEL1 NSF CSNP requested:FALSENSF L2 Restart state:RunningNSF L2 Restart retransmissions:0Maximum L2 NSF Restart retransmissions:3L2 NSF ACK requested:FALSEL2 NSF CSNP requested:FALSE
Troubleshooting Tips
To troubleshoot the NSF feature, use the following commands in privileged EXEC mode, as needed:
The following tips may help you to troubleshoot the device.
The system displays FIB errors.
Use the show cef state command to verify that distributed CEF switching is enabled on your platform. To enable distributed CEF, enter the ip cef distributed command in global configuration mode on the active RP.
Note
Cannot determine if an OSPF neighbor is NSF-aware.
To verify whether an OSPF neighbor device is NSF-aware and if NSF is operating between them, use the show ip ospf neighbor detail command.
The system loses, or appears to lose, adjacencies with network peers following a stateful switchover.
Use the show clns neighbors detail command to find any neighbors that do not have "NSF capable" and make sure that they are running NSF-aware images.
Additionally, for ISIS, the standby RP must be stable for 5 minutes (default) before another restart can be initiated. Use the nsf interval command to reset the restart period.
Configuration Examples
This section provides the following configuration examples:
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Configuring BGP NSF Example
The following example configures BGP NSF on a networking device:
router# configure terminalrouter(config)# router bgp 590router(config-router)# bgp graceful-restartConfiguring BGP NSF Neighbor Device Example
The following example configures BGP NSF on a neighbor router. All devices supporting BGP NSF must be NSF-aware, meaning that these devices recognize and advertise graceful restart capability.
router# configure terminalrouter(config)# router bgp 770router(config-router)# bgp graceful-restartConfiguring OSPF NSF Example
The following example configures OSPF NSF on a networking device:
router# configure terminalrouter(config)# router ospf 400router(config-router)# nsfConfiguring IS-IS NSF Example
The following example configures Cisco proprietary IS-IS NSF operation on a networking device:
router# configure terminalrouter(config)# router isisrouter(config-router)# nsf ciscoThe following example configures IS-IS NSF for IETF operation on a networking device:
router# configure terminalrouter(config)# router isisrouter(config-router)# nsf ietfCommand Reference
This section documents new and modified commands. All other commands used with this feature are documented in the Cisco IOS high-availability command reference publications for various releases.
New Commands
Modified Commands
bgp graceful-restart
To enable the Border Gateway Protocol (BGP) graceful restart capability, use the bgp graceful-restart command in router configuration mode. To remove this command from the configuration file and restore the system to its default condition with respect to this command, use the no form of this command.
bgp graceful-restart [restart-time seconds | stalepath-time seconds]
no bgp graceful-restart [restart-time seconds | stalepath-time seconds]
Syntax Description
Defaults
BGP Cisco Nonstop Forwarding (NSF) is disabled.
Command Modes
Router configuration
Command History
Usage Guidelines
The BGP graceful restart capability is negotiated in the OPEN message. If the user enters the bgp graceful-restart command after the BGP session is established, the session will need to be restarted.
When you enter the bgp graceful-restart command, the bgp graceful-restart restart-time and
bgp graceful-restart stalepath-time commands are enabled by default. After the bgp graceful-restart command is used to configure the graceful restart capability, you may tune the configuration using the restart-time and stalepath-time keywords. If you do not first configure the graceful restart capability using the bgp graceful-restart command, the tuning values will not appear in the configuration file.We recommend that the bgp graceful-restart restart-time and bgp graceful-restart stalepath-time commands remain set to their default values.
Examples
The following example shows how to configure the BGP graceful restart capability. Enter one command per line:
Router# configure terminalRouter(config)# router bgp 65001Router(config-router)# bgp graceful-restartRouter(config-router)# endRelated Commands
show ip bgp
Displays entries in the BGP routing table.
show ip bgp neighbors
Displays information about the TCP and BGP connections to neighbors.
clear ip cef epoch
To begin a new epoch and increment the epoch number for a Cisco Express Forwarding (CEF) table, use the clear ip cef epoch command in privileged EXEC mode. To remove this command from the configuration file and restore the system to its default condition with respect to this command, use the no form of this command.
clear ip cef epoch [all-vrfs | full | vrf [name]]
no clear ip cef epoch [all-vrfs | full | vrf [name]]
Syntax Description
Defaults
No default behavior or values.
Command Modes
Privileged EXEC
Command History
12.1(8a)EX
This command was introduced.
12.0(22)S
This command was introduced on Cisco 7500, 10000, 12000 series Internet routers.
Usage Guidelines
Use the clear ip cef epoch command when you want to rebuild a table. This command allows old and new table entries to be distinguished within the same data structure and allows you to retain the old CEF database table while constructing the new table.
Examples
The following example shows the output before and after you clear the epoch table and increment the epoch number:
router# show ip cef epochCEF epoch information:Table: Default-tableTable epoch: 2 (43 entries at this epoch)Adjacency tableTable epoch: 2 (5 entries at this epoch)router# clear ip cef epoch fullrouter# show ip cef epochCEF epoch information:Table: Default-tableTable epoch: 3 (43 entries at this epoch)Adjacency tableTable epoch: 3 (5 entries at this epoch)Related Commands
debug ip ospf nsf
To display debugging messages about Open Shortest Path First (OSPF) during a Cisco Nonstop Forwarding (NSF) restart, use the debug ip ospf nsf command in privileged EXEC mode. To disable the display of debugging output, use the no form of this command.
debug ip ospf nsf [detail]
no debug ip ospf nsf [detail]
Syntax Description
Command Modes
Privileged EXEC
Command History
Usage Guidelines
Use the debug ip ospf nsf command to diagnose problems with OSPF link-state database (LSDB) resynchronization and NSF operations.
Examples
The following example shows that OSPF NSF events debugging is enabled:
router# debug ip ospf nsfRelated Commands
debug isis nsf
To display information about the Intermediate System-to-Intermediate System (IS-IS) state during a Cisco Nonstop Forwarding (NSF) restart, use the debug isis nsf command in EXEC mode. To disable debugging output, use the no form of this command.
debug isis nsf [detail]
no debug isis nsf [detail]
Syntax Description
Command Modes
EXEC
Command History
Usage Guidelines
Use the debug isis nsf command to display basic information about the IS-IS state during an NSF restart. Use the debug isis nsf detail command to display additional IS-IS state detail during an NSF restart.
Examples
The following example displays IS-IS state information during an NSF restart:
router# debug isis nsfIS-IS NSF events debugging is onThe following example displays detailed IS-IS state information during an NSF restart:
router# debug isis nsf detailIS-IS NSF events (detailed) debugging is onrouter#Jan 24 20:04:54.090:%CLNS-5-ADJCHANGE:ISIS:Adjacency to gsr1 (GigabitEthernet2/0/0) Up, Standby adjacencyJan 24 20:04:54.090:ISIS-NSF:ADJ:000C.0000.0000 (Gi2/0/0), type 8/1, cnt 0/1, ht 10 (NEW)Jan 24 20:04:54.142:ISIS-NSF:Rcv LSP - L2 000B.0000.0000.00-00, seq 251, csum B0DC, ht 120, len 123 (local)Jan 24 20:04:55.510:ISIS-NSF:Rcv LSP - L1 000B.0000.0000.00-00, seq 23E, csum D20D, ht 120, len 100 (local)Jan 24 20:04:56.494:ISIS-NSF:ADJ:000C.0000.0000 (Gi2/0/0), type 8/0, cnt 0/1, ht 30Jan 24 20:04:56.502:ISIS-NSF:Rcv LSP - L1 000B.0000.0000.01-00, seq 21C, csum 413, ht 120, len 58 (local)Jan 24 20:04:58.230:ISIS-NSF:Rcv LSP - L2 000C.0000.0000.00-00, seq 11A, csum E197, ht 1194, len 88 (Gi2/0/0)Jan 24 20:05:00.554:ISIS-NSF:Rcv LSP - L1 000B.0000.0000.00-00, seq 23F, csum 1527, ht 120, len 111 (local)Related Commands
nsf (IS-IS)
To configure Cisco Nonstop Forwarding (NSF) operations for Intermediate System-to-Intermediate System (IS-IS), use the nsf command in router configuration IS-IS mode. To remove this command from the configuration file and restore the system to its default condition with respect to this command, use the no form of this command.
nsf [cisco | ietf]
no nsf [cisco | ietf]
Syntax Description
Defaults
NSF is disabled by default.
Command Modes
Router configuration IS-IS
Command History
Usage Guidelines
The user must configure NSF operation only if a router is expected to perform NSF during restart. The optional cisco keyword enables the use of checkpointing to allow the standby route processor (RP) to restore protocol state when an NSF restart occurs.
Examples
The following example enables Cisco proprietary IS-IS NSF operation:
nsf ciscoThe following example enables IETF IS-IS NSF operation:
nsf ietfRelated Commands
nsf (OSPF)
To configure Cisco Nonstop Forwarding (NSF) operations for Open Shortest Path First (OSPF), use the nsf command in router configuration OSPF mode. To remove this command from the configuration file and restore the system to its default condition with respect to this command, use the no form of this command.
nsf [enforce global]
no nsf [enforce global]
Syntax Description
enforce global
(Optional) Cancels NSF restart when non-NSF-aware neighboring networking devices are detected.
Defaults
NSF is disabled by default.
Command Modes
Router configuration OSPF
Command History
Usage Guidelines
In router configuration mode, enter OSPF mode to enter and use this command. The user must configure NSF operation only if a router is expected to perform NSF during restart. For users to have full NSF benefits, all neighbors of the specified router must be NSF-aware.
If non-NSF-aware neighbors are detected on a network interface, NSF restart is aborted on that interface; however, NSF restart will continue on other interfaces. This functionality applies to the default NSF mode of operation when NSF is configured.
If the user configures the optional enforce global keywords, NSF restart will be canceled for the entire process when non-NSF-aware neighbors are detected on any network interface during restart. To revert to the default NSF mode, configure the nsf command without any keywords.
Examples
The following example enters router configuration OSPF mode and cancels the NSF restart for the entire OSPF process if non-NSF-aware neighbors are detected on any network interface during restart:
router(config)# router ospf 1router(config-router)# nsf enforce globalRelated Commands
debug ip ospf nsf
Displays debugging messages related to OSPF NSF commands.
router ospf
Enables OSPF routing, which places the router in router configuration mode.
nsf interface wait
To specify how long a Cisco Nonstop Forwarding (NSF) restart will wait for all interfaces with Intermediate System-to-Intermediate System (IS-IS) adjacencies to come up before completing the restart, use the nsf interface wait command in router configuration IS-IS mode. To remove this command from the configuration file and restore the system to its default condition with respect to this command, use the no form of this command.
nsf interface wait seconds
no nsf interface wait seconds
Syntax Description
Defaults
The default value is 10 seconds.
Command Modes
Router configuration IS-IS
Command History
Usage Guidelines
The nsf interface wait command can be used if Cisco proprietary IS-IS NSF is configured or if Internet Engineering Task Force (IETF) IS-IS NSF is enabled using the nsf t3 manual command. You can use this command if an interface is slow to come up.
Examples
The following example specifies that NSF restart will wait 15 seconds for all interfaces with IS-IS adjacencies to come up before completing the restart:
router(config)# router isisrouter(config-router)# nsf ciscorouter(config-router)# nsf interface wait 15Related Commands
nsf interval
To configure the minimum time between Cisco Nonstop Forwarding (NSF) restart attempts, use the nsf interval command in router configuration Intermediate System-to-Intermediate System (IS-IS) mode. To remove this command from the configuration file and restore the system to its default condition with respect to this command, use the no form of this command.
nsf interval minutes
no nsf interval minutes
Syntax Description
minutes
The length of time in minutes between restart attempts. The valid range is from 0 to 1440 minutes.
Defaults
The default value is 5 minutes.
Command Modes
Router configuration IS-IS
Command History
Usage Guidelines
The nsf interval command can be used with both Cisco proprietary IS-IS NSF and Internet Engineering Task Force (IETF) IS-IS NSF. When you use Cisco proprietary IS-IS NSF, the active route processor (RP) must be up for at least 5 minutes before IS-IS will attempt to perform an NSF restart as part of a stateful switchover.
When you use the nsf command with the ietf keyword, the standby RP must be up for at least 5 minutes before IS-IS will attempt to perform an NSF restart as part of a stateful switchover.
Examples
The following example configures the minimum time between NSF restart attempts to be 2 minutes:
router(config-router)# router isisrouter(config-router)# nsf ciscorouter(config-router)# nsf interval 2Related Commands
nsf t3
To specify the methodology used to determine how long Internet Engineering Task Force (IETF) Cisco Nonstop Forwarding (NSF) will wait for the link-state packet (LSP) database to synchronize before generating overloaded link-state information for itself and flooding that information out to its neighbors, use the nsf t3 command in router configuration IS-IS mode. To remove this command from the configuration file and restore the system to its default condition with respect to this command, use the no form of this command.
nsf t3 {manual seconds | adjacency}
no nsf t3 {manual seconds | adjacency}
Syntax Description
Defaults
The default value is 30 seconds.
Command Modes
Router configuration IS-IS
Command History
Usage Guidelines
When the nsf t3 adjacency command is enabled, the time that IETF NSF waits for the LSP database to synchronize is determined by the adjacency holdtime advertised to the neighbors of the specified RP before switchover. When the nsf t3 manual command is enabled, the specified time in seconds is used.
The nsf t3 manual command can be used only if IETF IS-IS NSF is configured.
Examples
In the following example, the amount of time that IETF NSF waits for the LSP database to synchronize is set to 40 seconds:
nsf t3 manual 40In the following example, the amount of time that IETF NSF waits for the LSP database to synchronize is determined by the adjacency holdtime advertised to the neighbors of the specified RP before switchover:
nsf t3 adjacencyRelated Commands
show cef nsf
To show the current Cisco Nonstop Forwarding (NSF) state of Cisco Express Forwarding (CEF) on both the active and standby route processors (RPs), use the show cef nsf command in privileged EXEC mode.
show cef nsf
Syntax Description
The command has no arguments or keywords.
Command Modes
Privileged EXEC
Command History
Usage Guidelines
If you enter the show cef nsf command before a switchover occurs, no switchover activity is reported. After a switchover occurs, you can enter the show cef nsf command to display details about the switchover as reported by the newly active RP. On the Cisco 12000 and 7500 series Internet routers, details about line card switchover are also provided.
Examples
The following example shows the current NSF state:
router# show cef nsfLast switchover occurred: 00:01:30.088 agoRouting convergence duration: 00:00:34.728FIB stale entry purge durations:00:00:01.728 - Default00:00:00.088 - RedSwitchoverSlot Count Type Quiesce Period1 2 sso 00:00:00.1082 1 rpr+ 00:00:00.9483 2 sso 00:00:00.1525 2 sso 00:00:00.0926 1 rpr+ 00:00:00.632No NSF stats available for the following linecards:4 7Table 2 describes the significant fields in the display.
Related Commands
clear ip cef epoch
Begins a new epoch and increments the epoch number for a CEF table.
show cef state
Displays the state of CEF on a networking device.
show cef state
To display the state of Cisco Express Forwarding (CEF) on a networking device, use the show cef state command in privileged EXEC mode.
show cef state
Syntax Description
The command has no arguments or keywords.
Command Modes
Privileged EXEC
Command History
12.0(22)S
This command was introduced on Cisco 7500, 10000, and 12000 series Internet routers.
Examples
The following example shows the state of CEF on the active route processor (RP):
router# show cef stateRRP state:I am standby RRP: noRF Peer Presence: yesRF PeerComm reached: yesRedundancy mode: SSO(7)CEF NSF: enabled/runningThe following example shows the state of CEF on the standby RP:
router# show cef stateRRP state:I am standby RRP: yesMy logical slot: 0RF Peer Presence: yesRF PeerComm reached: yesCEF NSF: runningRelated Commands
clear ip cef epoch
Begins a new epoch and increments the epoch number for a CEF table.
show cef nsf
Displays the current NSF state of CEF on both the active and standby RPs.
show clns neighbors
To display both end systems (ES) and intermediate systems (IS) neighbors, use the show clns neighbors command in EXEC mode.
show clns area-tag neighbors [interface-type interface-number] [detail]
Syntax Description
Command Modes
EXEC
Command History
10.0
This command was introduced.
12.0(5)T
The area and detail keywords were added.
12.0(22)S
The "NSF capable" line was added to the output.
Examples
The following is sample output from the show clns neighbors command. This display is a composite of the show clns es-neighbor and show clns is-neighbor commands.
Router# show clns neighborsSystem Id Interface SNPA State Holdtime Type Protocol000A.0000.0000 Se3/0/2 *HDLC* Stby 30 L1L2 IS-IS000C.0000.0000 Gi2/0/0 000c.0000.0000 Stby 30 L1L2 IS-ISTable 3 describes the significant fields shown in the display.
The following is sample output from the show clns neighbors detail command:
Router# show clns neighbors detailSystem Id SNPA Interface State Holdtime Type ProtocolRouter2 Se0 *HDLC* Up 25 L1L2 IS-ISArea Address(es):49IP Address(es): 10.16.255.255*Uptime:6d23hNSF capableNotice that the information displayed in the show clns neighbors detail output includes everything shown in the show clns neighbors output in addition to the area address associated with the IS neighbor and its uptime. When IP routing is enabled, Integrated-ISIS adds information to the output of the show clns commands. The show clns neighbors detail command output shows the IP addresses that are defined for the directly connected interface and an asterisk (*) to indicate which IP address is the next hop.
Related Commands
clear clns neighbors
Removes CLNS neighbor information from the adjacency database.
show ip bgp
To display entries in the Border Gateway Protocol (BGP) routing table, use the show ip bgp command in user EXEC mode.
show ip bgp [network] [network-mask] [longer-prefixes]
Syntax Description
Command Modes
User EXEC
Command History
Examples
The following example is from the show ip bgp command:
router# show ip bgpBGP table version is 9, local router ID is a.a.a.aStatus codes:s suppressed, d damped, h history, * valid, > best, i - internal,S StaleOrigin codes:i - IGP, e - EGP, ? - incompleteNetwork Next Hop Metric LocPrf Weight PathS> 10.100.100.0/24 192.168.2.2 0 0 65002 iS> 10.10.0.0 192.168.2.2 0 65002 65003 iS> 10.20.0.0 192.168.2.2 0 65002 65003 iS> 10.30.0.0/8 192.168.2.2 0 65002 65003 iS> 10.40.33.0/24 192.168.2.2 0 65002 65003 i*> 0.0.0.0 0 32768 iS> 10.50.0.0/8 192.168.2.2 0 65002 65003 iS> 10.60.100.0 192.168.2.2 0 0 65002 iS> 10.70.200.0 192.168.2.2 0 0 65002 iTable 4 describes the significant fields shown in the displays.
The following example of the show ip bgp command specifies a network:
router# show ip bgp 10.0.0.0BGP routing table entry for 10.0.0.0/8, version 7Paths:(1 available, best #1, table Default-IP-Routing-Table)Not advertised to any peer65002 65003, (stale)192.168.2.2 from 192.168.2.2 (0.0.0.0)Origin IGP, localpref 100, valid, external, bestrouter#Related Commands
bgp graceful-restart
Enables the BGP graceful restart capability.
show ip bgp neighbors
Displays information about the TCP and BGP connections to neighbors.
show ip bgp neighbors
To display information about TCP/IP and Border Gateway Protocol (BGP) connections to neighbors, use the show ip bgp neighbors command in EXEC mode.
show ip bgp neighbors [neighbor-address] [received-routes | routes | advertised-routes | {paths regexp} | dampened-routes] [received prefix-filter]
Syntax Description
Command Modes
EXEC
Command History
Examples
The following is sample output from the show ip bgp neighbors command in privileged EXEC mode.
Router# show ip bgp neighbors 172.16.254.3BGP neighbor is 172.16.254.3, remote AS 150, internal linkBGP version 4, remote router ID 172.16.254.3BGP state = Established, up for 19:24:07Last read 00:00:06, hold time is 180, keepalive interval is 60 secondsNeighbor capabilities:Route refresh:advertised and received(new)Address family IPv4 Unicast:advertised and receivedGraceful Restart Capabilty:advertised and receivedRemote Restart timer is 120 secondsAddress families preserved by peer:IPv4 UnicastReceived 4231 messages, 0 notifications, 0 in queueSent 4167 messages, 0 notifications, 0 in queueDefault minimum time between advertisement runs is 5 secondsFor address family:IPv4 UnicastBGP table version 159559, neighbor version 159559Index 90, Offset 11, Mask 0x4Route refresh request:received 0, sent 010031 accepted prefixes consume 441364 bytesPrefix advertised 29403, suppressed 0, withdrawn 9801Number of NLRIs in the update sent:max 242, min 0Connections established 2; dropped 1Last reset 19:26:54, due to NSF peer closed the sessionConnection state is ESTAB, I/O status:1, unread input bytes:0Local host:150.254.254.2, Local port:11005Foreign host:172.16.254.3, Foreign port:179Enqueued packets for retransmit:0, input:0 mis-ordered:0 (0 bytes)Event Timers (current time is 0x4371A84):Timer Starts Wakeups NextRetrans 1380 22 0x0TimeWait 0 0 0x0AckHold 1377 870 0x0SendWnd 0 0 0x0KeepAlive 0 0 0x0GiveUp 0 0 0x0PmtuAger 0 0 0x0DeadWait 0 0 0x0iss:1875330775 snduna:1875639119 sndnxt:1875639119 sndwnd: 16308irs:3577079138 rcvnxt:3577393901 rcvwnd: 16137 delrcvwnd: 247SRTT:300 ms, RTTO:607 ms, RTV:3 ms, KRTT:0 msminRTT:0 ms, maxRTT:408 ms, ACK hold:200 msFlags:higher precedence, nagleDatagrams (max data segment is 536 bytes):Rcvd:2984 (out of order:1), with data:1800, total data bytes:314762Sent:3190 (retransmit:22, fastretransmit:0), with data:1751, total data bytes:308343Table 5 describes the significant fields shown in the display.
The following is sample output from the show ip bgp neighbors command with the advertised-routes keyword in privileged EXEC mode:
Router# show ip bgp neighbors 172.16.232.178 advertised-routesBGP table version is 27, local router ID is 172.16.232.181Status codes: s suppressed, d damped, h history, * valid, > best, i - internalOrigin codes: i - IGP, e - EGP, ? - incompleteNetwork Next Hop Metric LocPrf Weight Path*>i110.0.0.0 172.16.232.179 0 100 0 ?*> 200.2.2.0 0.0.0.0 0 32768 iThe following is sample output from the show ip bgp neighbors command with the routes keyword in privileged EXEC mode:
Router# show ip bgp neighbors 172.16.232.178 routesBGP table version is 27, local router ID is 172.16.232.181Status codes: s suppressed, d damped, h history, * valid, > best, i - internalOrigin codes: i - IGP, e - EGP, ? - incompleteNetwork Next Hop Metric LocPrf Weight Path*> 10.0.0.0 172.16.232.178 40 0 10 ?*> gg.0.0.0 172.16.232.178 40 0 10 ?Table 6 describes the significant fields shown in the displays.
The following is sample output from the show ip bgp neighbors command with the paths keyword in privileged EXEC mode:
Router# show ip bgp neighbors 171.69.232.178 paths ^10Address Refcount Metric Path0x60E577B0 2 40 10 ?Table 7 describes the significant fields shown in the display.
The following is sample output from the show ip bgp neighbors command with the received prefix-filter keyword in privileged EXEC mode:
Router# show ip bgp neighbor 192.168.20.72 received prefix-filterAddress family:IPv4 Unicastip prefix-list 192.168.20.72:1 entriesseq 5 deny 10.0.0.0/8 le 32Table 8 describes the significant fields shown in the display.
show ip cef
To display entries in the Forwarding Information Base (FIB) or to display a summary for the FIB, use the show ip cef command in privileged EXEC mode.
show ip cef [vrf vrf-name] [unresolved | [detail | summary]
Specific FIB Entries Based on Stateful Switchover
show ip cef [epoch]
Specific FIB Entries Based on IP Address Information
show ip cef [vrf vrf-name] [network [mask]] [longer-prefixes] [detail]
Specific FIB Entries Based on Nonrecursive Routes
show ip cef [vrf vrf-name] nonrecursive [detail]
Syntax Description
Command Modes
Privileged EXEC
Command History
Usage Guidelines
The show ip cef command without any keywords or arguments shows a brief display of all FIB entries.
The show ip cef detail command shows detailed FIB entry information for all FIB entries.
The show ip cef summary command shows a summary of FIB entry information for all FIB entries.
Examples
The following is sample output from the show ip cef unresolved command:
Router# show ip cef unresolvedIP Distributed CEF with switching (Table Version 136632)45776 routes, 13 unresolved routes (0 old, 13 new)45776 leaves, 2868 nodes, 8441480 bytes, 136632 inserts, 90856 invalidations1 load sharing elements, 208 bytes, 1 references1 CEF resets, 1 revisions of existing leavesrefcounts: 527292 leaf, 465617 node10.214.0.0/16, version 1366220 packets, 0 bytesvia 171.69.233.56, 0 dependencies, recursiveunresolved10.215.0.0/16, version 1366230 packets, 0 bytesvia 171.69.233.56, 0 dependencies, recursiveunresolved10.218.0.0/16, version 1366240 packets, 0 bytesThe following is sample output from the show ip cef summary command on the active route processor (RP), after a switchover has occurred:
Router# show ip cef summaryNon-stop forwarding:13 routes at switchover11 routes available after convergence (2 purged)The following is sample output from a system that is not running Cisco Express Forwarding (CEF) Nonstop Forwarding (NSF), after a switchover has occurred:
router# show ip cef summaryNon-stop forwarding:CEF NSF was not running at switchover5 routes available after convergence (0 purged)The following is sample output from the show ip cef detail command for Ethernet interface 0. It shows all the prefixes resolving through adjacency pointing to next hop Ethernet interface 0/0 and next hop interface IP address 172.19.233.33.
Router# show ip cef detailIP Distributed CEF with switching (Table Version 136808)45800 routes, 8 unresolved routes (0 old, 8 new) 45800 leaves, 2868 nodes, 8444360 bytes,136808 inserts, 91008 invalidations 1 load sharing elements, 208 bytes, 1 references 1CEF resets, 1 revisions of existing leaves refcounts: 527343 leaf, 465638 node172.19.233.33/32, version 7417, cached adjacency 172.19.233.33 0 packets, 0 bytes,Adjacency-prefixvia 172.19.233.33, Ethernet0/0, 0 dependenciesnext hop 172.19.233.33, Ethernet0/0valid cached adjacencyThe following example shows output from the show ip cef epoch command:
Router#show ip cef epochCEF epoch information:Table: DefaultTable epoch: 0 (35 entries at this epoch)Adjacency tableTable epoch: 0 (7 entries at this epoch)Table 9 describes the significant fields shown in the display.
The following example shows the forwarding table associated with the VRF named vrf1:
Router# show ip cef vrf vrf1Prefix Next Hop Interface10.0.0.0/32 receive10.10.0.0/8 10.60.0.1 Ethernet1/310.20.0.0/8 10.62.0.2 POS6/010.50.0.0/8 attached Ethernet1/310.50.0.0/32 receive10.60.0.1/32 10.62.0.1 Ethernet1/310.60.0.2/32 receive10.255.255.255/32 receive10.62.0.0/8 52.0.0.2 POS6/0192.168.0.0/24 receive192.168.255.255/32 receiveTable 10 describes the significant fields shown in the display.
Related Commands
clear ip cef epoch
Begins a new epoch and increments the epoch number for a CEF table.
show cef state
Displays the state of CEF on a networking device.
show ip ospf
To display general information about Open Shortest Path First (OSPF) routing processes, use the show ip ospf command in user EXEC mode.
show ip ospf [process-id]
Syntax Description
process-id
(Optional) Process ID. If this argument is included, only information for the specified routing process is included.
Command Modes
User EXEC
Command History
10.0
This command was introduced.
12.0(22)S
Fields of information were added to the command output.
Examples
The following example output is from the show ip ospf command when entered without a specific OSPF process ID:
router> show ip ospfRouting Process "ospf 1" with ID 10.2.2.2 and Domain ID 10.0.0.1Supports only single TOS(TOS0) routesSupports opaque LSASPF schedule delay 5 secs, Hold time between two SPFs 10 secsMinimum LSA interval 5 secs. Minimum LSA arrival 1 secsNumber of external LSA 0. Checksum Sum 0x0Number of opaque AS LSA 0. Checksum Sum 0x0Number of DCbitless external and opaque AS LSA 0Number of DoNotAge external and opaque AS LSA 0Number of areas in this router is 1. 1 normal 0 stub 0 nssaExternal flood list length 0cisco Non-Stop Forwarding enabled, last NSF restart 00:02:06 ago (took 44 secs)Area BACKBONE(0)Number of interfaces in this area is 1 (0 loopback)Area has no authenticationSPF algorithm executed 3 timesTable 11 describes the significant fields shown in the display.
Related Commands
debug ip ospf nsf
Displays debugging messages related to OSPF NSF commands.
show ip ospf neighbor
Displays OSPF-neighbor information on a per-interface basis.
show ip ospf neighbor
To display Open Shortest Path First (OSPF)-neighbor information on a per-interface basis, use the show ip ospf neighbor command in user EXEC mode.
show ip ospf neighbor [interface-type interface-number] [neighbor-id] [detail]
Syntax Description
Command Modes
User EXEC
Command History
10.0
This command was introduced.
12.0(22)S
Fields of information were added to the command output.
Examples
The following is sample output from the show ip ospf neighbor detail command:
router> show ip ospf neighbor detailNeighbor 10.3.3.3, interface address 172.16.10.3In the area 0 via interface POS3/0Neighbor priority is 0, State is FULL, 6 state changesDR is 10.0.0.0 BDR is 10.0.0.0Options is 0x52LLS Options is 0x1 (LR), last OOB-Resync 00:02:22 agoDead timer due in 00:00:37Neighbor is up for 00:03:07Index 1/1, retransmission queue length 0, number of retransmission 1First 0x0(0)/0x0(0) Next 0x0(0)/0x0(0)Last retransmission scan length is 1, maximum is 1Last retransmission scan time is 0 msec, maximum is 0 msecTable 12 describes the significant fields shown in the display.
Related Commands
debug ip ospf nsf
Displays debugging messages related to OSPF NSF commands.
show ip ospf
Displays general information about OSPF routing processes.
show isis nsf
To display current state information regarding Intermediate System-to-Intermediate System (IS-IS) Cisco Nonstop Forwarding (NSF), use the show isis nsf command in EXEC mode.
show isis nsf
Syntax Description
This command has no arguments or keywords.
Command Modes
EXEC
Command History
Usage Guidelines
The show isis nsf command can be used with both Cisco proprietary IS-IS NSF and Internet Engineering Task Force (IETF) IS-IS NSF. The information displayed when this command is entered depends on which protocol has been configured. To configure nsf for a specific routing protocol, use the router bgp, router ospf, or router isis commands in global configuration mode.
Examples
The following example shows state information for an active RP that is configured to use Cisco proprietary IS-IS NSF:
router# show isis nsfNSF enabled, mode 'cisco'RP is ACTIVE, standby ready, bulk sync completeNSF interval timer expired (NSF restart enabled)Checkpointing enabled, no errorsLocal state:ACTIVE, Peer state:STANDBY HOT, Mode:SSOThe following example shows state information for a standby RP that is configured to use Cisco proprietary IS-IS NSF:
router# show isis nsfNSF enabled, mode 'cisco'RP is STANDBY, chkpt msg receive count:ADJ 2, LSP 314NSF interval timer notification received (NSF restart enabled)Checkpointing enabled, no errorsLocal state:STANDBY HOT, Peer state:ACTIVE, Mode:SSOThe following example shows state information when the networking device is configured to use IETF IS-IS NSF:
router# show isis nsfNSF is ENABLED, mode IETFNSF pdb state:InactiveNSF L1 active interfaces:0NSF L1 active LSPs:0NSF interfaces awaiting L1 CSNP:0Awaiting L1 LSPs:NSF L2 active interfaces:0NSF L2 active LSPs:0NSF interfaces awaiting L2 CSNP:0Awaiting L2 LSPs:Interface:Serial3/0/2NSF L1 Restart state:RunningNSF p2p Restart retransmissions:0Maximum L1 NSF Restart retransmissions:3L1 NSF ACK requested:FALSEL1 NSF CSNP requested:FALSENSF L2 Restart state:RunningNSF p2p Restart retransmissions:0Maximum L2 NSF Restart retransmissions:3L2 NSF ACK requested:FALSEInterface:GigabitEthernet2/0/0NSF L1 Restart state:RunningNSF L1 Restart retransmissions:0Maximum L1 NSF Restart retransmissions:3L1 NSF ACK requested:FALSEL1 NSF CSNP requested:FALSENSF L2 Restart state:RunningNSF L2 Restart retransmissions:0Maximum L2 NSF Restart retransmissions:3L2 NSF ACK requested:FALSEL2 NSF CSNP requested:FALSERelated Commands
