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Table Of Contents
Prerequisites for OER BGP Inbound Optimization
Information About OER BGP Inbound Optimization
OER Inbound Optimization Using BGP
How to Configure OER BGP Inbound Optimization
Configuring OER to Automatically Learn Inside Prefixes
Manually Selecting Inside Prefixes for OER Monitoring
Applying a Policy to Learned Inside Prefixes
Applying a Policy to Configured Inside Prefixes
Configuration Examples for OER BGP Inbound Optimization
Configuring OER to Automatically Learn Inside Prefixes: Example
Manually Selecting Inside Prefixes for OER Monitoring: Example
Applying a Policy to Learned Inside Prefixes: Example
Applying a Policy to Configured Inside Prefixes: Example
Feature Information for OER BGP Inbound Optimization
OER BGP Inbound Optimization
First Published: June 19, 2006Last Updated: June 19, 2006Optimized Edge Routing (OER) Border Gateway Protocol (BGP) inbound optimization supports best entrance selection for traffic that originates from prefixes outside an autonomous system destined for prefixes inside the autonomous system. External BGP (eBGP) advertisements from an autonomous system to another autonomous system (for example, an Internet service provider) can influence the entrance path for traffic entering the network. OER uses eBGP advertisements to manipulate the best entrance selection.
Finding Feature Information in This Module
Your Cisco IOS software release may not support all of the features documented in this module. To reach links to specific feature documentation in this module and to see a list of the releases in which each feature is supported, use the "Feature Information for OER BGP Inbound Optimization" section.
Finding Support Information for Platforms and Cisco IOS Software Images
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Contents
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Prerequisites for OER BGP Inbound Optimization
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Prerequisites for OER BGP Inbound Optimization
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Information About OER BGP Inbound Optimization
To configure OER BGP inbound optimization, you should understand the following concepts:
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OER Inside Prefixes
An OER inside prefix is defined as a public IP prefix assigned to a company. An OER outside prefix is defined as a public IP prefix assigned outside the company. Companies advertise the inside prefixes over the Internet using an Internet service provider (ISP) and receive advertisements for outside prefixes from an ISP.
OER Inbound Optimization Using BGP
A network advertises reachability of its inside prefixes to the Internet using eBGP advertisements to its ISPs. If the same prefix is advertised to more than one ISP, then the network is multihoming. OER BGP inbound optimization works best with multihomed networks, but it can also be used with a network that has multiple connections to the same ISP. To implement BGP inbound optimization, OER manipulates eBGP advertisements to influence the best entrance selection for traffic bound for inside prefixes. The benefit of implementing the best entrance selection is limited to a network that has more than one ISP connection.
OER can use four methods to influence the best entrance selection of an inside prefix into the network:
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Withdraw
OER can prevent the advertisement of an inside prefix in eBGP over an OER external interface. When the inside prefix advertisement is withdrawn, an external autonomous system such as an ISP will remove the route from the routing information base (RIB). The link over that interface is no longer considered an entrance for the withdrawn inside prefix. Prefix traffic will be distributed over the other entrances where the inside prefix is still advertised. If OER prevents the advertisement of an inside prefix over every link except one, then there is only a single entrance into the network for the withdrawn inside prefix.
If OER withdraws an inside prefix from eBGP on an OER external interface, Reverse Path Forwarding (RPF) checking at an ISP may drop all packets exiting the OER external interface that use the withdrawn inside prefix. Another issue that must be considered is that if OER withdraws an inside prefix, then that entrance is no longer available if an outage occurs on other entrances. Summary routes can be configured in the network to handle both these issues.
Autonomous System Number Prepend
After OER selects a best entrance for an inside prefix, extra autonomous system hops are prepended to the inside prefix BGP advertisement over the other entrances. The extra autonomous system hops on the other entrances increase the probability that the best entrance will be used for the inside prefix. If you use this method of inbound optimization and a change is made to an autonomous system, you must issue a soft outbound reconfiguration using the clear ip bgp command.
Autonomous System Number Community Prepend
After OER selects a best entrance for an inside prefix, a BGP prepend community is attached to the inside prefix BGP advertisement from the network to another autonomous system such as an ISP. The BGP prepend community will increase the number of autonomous system hops in the advertisement of the inside prefix from the ISP to its peers. Autonomous system prepend BGP community is the preferred method to be used for OER BGP inbound optimization because there is no risk of the local ISP filtering the extra autonomous system hops. There are some issues, for example, not all ISPs support the BGP prepend community, ISP policies may ignore or modify the autonomous system hops, and a transit ISP may filter the autonomous system path.
Local Preference BGP Community
Within a BGP autonomous system, the Local_Pref attribute is included in all update messages between BGP peers. If there are several paths to the same destination, the Local_Pref attribute with the highest value indicates the preferred outbound path from the local autonomous system. The highest ranking route is advertised to internal peers. The Local_Pref value is not forwarded to external peers.
After OER selects a best entrance for an inside prefix, a local preference BGP community is attached to the inside prefix when advertised from the network to another autonomous system such as an ISP over the best entrance (OER external interface). The ISP advertises the inside prefix within the ISP network using the specified Local_Pref value. BGP will choose the path with the highest Local_Pref value because Local_Pref is the highest priority method for selecting a route, and this method ensures that the best entrance can be enforced within the ISP.
There are some issues, for example, not all ISPs support the BGP Local_Pref community, ISPs do not usually advertise BGP Local_Pref communities to each other, and each provider must apply the same default Local_Pref value to a prefix regardless of the origin of the advertisement.
How to Configure OER BGP Inbound Optimization
To optimize traffic routing, subsets of the total traffic must be identified in the OER learn phase, and these traffic subsets are named traffic class flows (TCF) entries. To configure OER BGP inbound optimization the OER master controller can either be configured to automatically learn the TCF entries, or the TCF entries can be manually configured. After the inside prefixes are identified and monitored, a policy can be applied to determine the best entrance for the inside prefixes. This section contains the following tasks:
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Configuring OER to Automatically Learn Inside Prefixes
Perform this task to configure an OER master controller to automatically learn inside prefixes to be used as TCF entries to be entered in the Monitored Traffic Class (MTC) list. This task is configured at the master controller. The learn command is entered in OER master controller configuration mode and is required to enter OER Top Talker and Top Delay configuration mode. This task configures prefix learning of the inside prefixes (prefixes within the network). Optional configuration parameters such as learning period timers, maximum number of prefixes, and an expiration time for MTC list entries are also shown.
Prerequisites
Before configuring this task, BGP peering for internal and external BGP neighbors must be configured.
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DETAILED STEPS
What to Do Next
This section shows how to configure automatic prefix learning for inside prefixes. To configure specific prefixes for monitoring and optimization, see the "Manually Selecting Inside Prefixes for OER Monitoring" section. To apply an OER policy to the learned prefixes, see the "Applying a Policy to Learned Inside Prefixes" section.
Manually Selecting Inside Prefixes for OER Monitoring
Perform this task to manually select inside prefixes for monitoring. An IP prefix list is created to define the inside prefix or prefix range. The prefix list is then imported into the central policy database by configuring a match clause in an OER map. The following IP prefix list configuration options are supported:
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Manually Excluding Prefixes
An IP prefix list with a deny statement is used to configure the master controller to exclude a prefix or prefix length. Deny prefix list sequences should be applied in the lowest oer map sequences for best performance.
OER Map Operation
The operation of an OER map is similar to the operation of a route-map. An OER map is configured to select an IP prefix list or OER learn policy using a match clause and then to apply OER policy configurations using a set clause. The OER map is configured with a sequence number like a route-map, and the OER map with the lowest sequence number is evaluated first.
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DETAILED STEPS
What to Do Next
This section shows how to configure manual prefix learning for inside prefixes. To apply an OER policy to the configured prefixes, see the "Applying a Policy to Configured Inside Prefixes" section.
Applying a Policy to Learned Inside Prefixes
Perform this task to apply a policy to learned inside prefix TCF entries from the MTC list. The policy is configured using an OER map and contains some set clauses.
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Applying a Policy to Configured Inside Prefixes
Perform this task to apply a policy to configured inside prefix TCF entries from the MTC list. The policies are configured using an OER map. This task contains prefix list configuration with different criteria in the set clauses.
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Configuration Examples for OER BGP Inbound Optimization
This section contains the following configuration examples:
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Configuring OER to Automatically Learn Inside Prefixes: Example
The following example shows how to configure OER to automatically learn prefixes inside the network:
Router> enableRouter# configure terminalRouter(config)# oer masterRouter(config-oer-mc)# learnRouter(config-oer-mc-learn)# inside bgpRouter(config-oer-mc-learn)# aggregation-type bgpRouter(config-oer-mc-learn)# monitor-period 10Router(config-oer-mc-learn)# periodic-interval 20Router(config-oer-mc-learn)# prefixes 500Router(config-oer-mc-learn)# endManually Selecting Inside Prefixes for OER Monitoring: Example
The following example shows how to manually configure OER to learn prefixes inside the network using an OER map:
Router> enableRouter# configure terminalRouter(config)# ip prefix-list INSIDE_PREFIXES seq 20 permit 192.168.1.0/24Router(config)# oer-map INSIDE_MAP 10Router(config-oer-map)# match ip address prefix-list INSIDE_PREFIXES insideRouter(config-oer-map)# endApplying a Policy to Learned Inside Prefixes: Example
The following example shows how to apply an OER policy to learned inside prefixes:
Router> enableRouter# configure terminalRouter(config)# oer-map INSIDE_LEARN 10Router(config-oer-map)# match oer learn insideRouter(config-oer-map)# set delay threshold 2000Router(config-oer-map)# set loss relative 200Router(config-oer-map)# set unreachable relative 100Router(config-oer-map)# endApplying a Policy to Configured Inside Prefixes: Example
The following example shows how to create an OER map named INSIDE_CONFIGURE and apply an OER policy to manually configured inside prefixes:
Router> enableRouter# configure terminalRouter(config)# oer-map INSIDE_CONFIGURE 10Router(config-oer-map)# match ip address prefix-list INSIDE_PREFIXES insideRouter(config-oer-map)# set delay threshold 2000Router(config-oer-map)# set loss relative 200Router(config-oer-map)# set unreachable relative 100Router(config-oer-map)# endWhere to Go Next
For an overview of the OER technology and more details about implementing OER, see the Cisco IOS Optimized Edge Routing Configuration Guide, Release 12.4T.
Additional References
The following sections provide references related to OER BGP inbound optimization.
Related Documents
OER configuration concepts, tasks, and examples
Cisco IOS Optimized Edge Routing Configuration Guide, Release 12.4T
Cisco OER commands: complete command syntax, command mode, command history, defaults, usage guidelines and examples
Cisco IOS Optimized Edge Routing Command Reference, Release 12.4T
IP Routing Protocol commands
Cisco IOS IP Routing Protocols Command Reference, Release 12.4T
IP Routing Protocol configuration tasks
Cisco IOS IP Routing Protocols Configuration Guide, Release 12.4
Standards
No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.
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MIBs
RFCs
No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.
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Technical Assistance
Command Reference
This section documents new and modified commands only.
clear oer master prefix
To clear Optimized Edge Routing (OER) controlled prefixes from the master controller database, use the clear oer master prefix command in privileged EXEC mode.
clear oer master prefix {* | prefix | inside * | learned [inside]}
Syntax Description
*
Clears all prefixes.
prefix
Clears a single prefix or prefix range. The prefix address and mask are entered with this argument.
inside
Clears inside prefixes.
learned
Clears learned prefixes.
Command Modes
Privileged EXEC
Command History
12.3(8)T
This command was introduced.
12.4(9)T
The inside keyword was added to support OER Border Gateway Protocol (BGP) inbound optimization.
Usage Guidelines
The clear oer master prefix command is entered on a master controller.
Examples
The following example clears learned prefixes:
Router# clear oer master prefix learnedThe following example clears all inside prefixes:
Router# clear oer master prefix inside *Related Commands
oer
Enables an OER process and configures a router as an OER border router or as an OER master controller.
inside bgp
To configure Optimized Edge Routing (OER) to learn the inside prefixes within a network, use the inside bgp command in OER Top Talker and Top Delay learning configuration mode. To disable prefix learning of inside prefixes, use the no form of this command.
inside bgp
no inside bgp
Syntax Description
This command has no arguments or keywords.
Command Default
No inside prefixes are learned by OER.
Command Modes
OER Top Talker and Top Delay learning configuration
Command History
Usage Guidelines
This command is used to implement OER Border Gateway Protocol (BGP) inbound optimization by identifying the prefixes within a network (inside prefixes). OER BGP inbound optimization supports best entrance selection for traffic that originates from prefixes outside an autonomous system destined for prefixes inside the autonomous system. External BGP (eBGP) advertisements from an autonomous system to another autonomous system (for example, an Internet service provider [ISP]) can influence the entrance path for traffic entering the network. OER uses eBGP advertisements to manipulate the best entrance selection.
Examples
The following example shows how to configure an OER master controller to automatically learn the inside prefixes in a network:
oer masterlearninside bgpRelated Commands
match ip address (OER)
To reference an extended IP access list or IP prefix as match criteria in an Optimized Edge Routing (OER) map, use the match ip address command in OER map configuration mode. To delete the match clause entry, use the no form of this command.
match ip address {access-list name | prefix-list name [inside]}
no match ip address
Syntax Description
Defaults
No match is performed.
Command Modes
OER map configuration
Command History
Usage Guidelines
The match ip address command defines a policy, defined by the oer-map command, to a list of prefixes. The match ip address command is entered on a master controller in OER map configuration mode. This command is used to configure a named extended access list or IP prefix list as a match criteria in an OER map. Only one match clause can be configured for each OER map sequence. The access list is created with the ip access-list command. Only named extended IP access lists are supported. The IP prefix list is created with the ip prefix-list command. A prefix can be any IP network number combined with a prefix mask that specifies the prefix length.
The inside keyword is used to support OER BGP inbound optimization that supports best entrance selection for traffic that originates from prefixes outside an autonomous system destined for prefixes inside the autonomous system. External BGP (eBGP) advertisements from an autonomous system to an Internet service provider (ISP) can influence the entrance path for traffic entering the network. OER uses eBGP advertisements to manipulate the best entrance selection.
Examples
The following example creates a prefix list named CUSTOMER. The prefix list creates a filter for the 10.4.9.0/24 network. The match ip address command configures the prefix list as match criterion in an OER map.
Router(config)# ip prefix-list CUSTOMER permit 10.4.9.0/24Router(config)# oer-map SELECT_EXIT 10Router(config-oer-map)# match ip address prefix-list CUSTOMERRouter(config-oer-map)# set mode select-exit goodThe following example creates an extended access list named FTP. The named extended access list creates a filter for FTP traffic that is sourced from the 10.1.1.0/24 network. The match ip address command configures the access list as match criterion in an OER map. FTP traffic is policy routed to the first in-policy exit.
Router(config)# ip access-list extended FTPRouter(config-ext-nacl)# permit tcp 10.1.1.0 0.0.0.255 any eq ftpRouter(config-ext-nacl)# exitRouter(config)# oer-map SELECT_EXIT 10Router(config-oer-map)# match ip address access-list FTPRouter(config-oer-map)# set mode select-exit goodThe following example creates a prefix list named INSIDE1. The prefix list creates a filter for the 10.2.2.0/24 network. The match ip address command configures the prefix list as match criterion in an OER map.
Router(config)# ip prefix-list INSIDE1 seq 5 permit 10.2.2.0/24Router(config)# oer-map INSIDE_PREFIXES 10Router(config-oer-map)# match ip address prefix-list INSIDE1 insideRouter(config-oer-map)# set as-path prepend 45000Related Commands
match oer learn
To create a match clause entry in an Optimized Edge Routing (OER) map to match OER learned prefixes, use the match oer learn command in OER map configuration mode. To delete the match clause entry, use the no form of this command.
match oer learn {delay | inside | throughput}
no match oer learn {delay | inside | throughput}
Syntax Description
Defaults
No default behavior or values
Command Modes
OER map configuration
Command History
Usage Guidelines
The match oer learn command is entered on a master controller in OER map configuration mode. OER can be configured to learn prefixes based on delay, inside prefix, or throughput. This command is used to configure OER learned prefixes as match criteria in an OER map. Only one match clause can be configured for each OER map sequence.
Examples
The following example creates an OER map named DELAY that matches traffic learned based on delay. The set clause applies a route control policy that configures OER to actively control this traffic.
Router(config)# oer-map DELAY 20Router(config-oer-map)# match oer learn delayRouter(config-oer-map)# set mode route controlThe following example creates an OER map named THROUGHPUT that matches traffic learned based on throughput. The set clause applies a route control policy that configures OER to actively control this traffic.
Router(config)# oer-map THROUGHPUT 30Router(config-oer-map)# match oer learn throughputRouter(config-oer-map)# set mode route controlThe following example creates an OER map named INSIDE that matches traffic learned based on inside prefixes. The set clause applies a route control policy that configures OER to actively control this traffic.
Router(config)# oer-map INSIDE 40Router(config-oer-map)# match oer learn insideRouter(config-oer-map)# set mode route controlRelated Commands
show oer master prefix
To display the status of monitored prefixes, use the show oer master prefix command in privileged EXEC mode.
show oer master prefix [detail | inside [detail] | learned [delay | inside | throughput] | prefix [detail | policy | traceroute [exit-id | border-address | current] [now]]]
Syntax Description
Command Modes
Privileged EXEC
Command History
Usage Guidelines
The show oer master prefix command is entered on a master controller. This command is used to display the status of monitored prefixes. The output from this command includes information about the source border router, current exit interface, prefix delay, and egress and ingress interface bandwidth. The output can be filtered to display information for only a single prefix, learned prefixes, inside prefixes, and prefixes learned based on delay or throughput.
The traceroute keyword is used to display traceroute probe results. The output generated by this keyword provides hop by hop statistics to the probe target network. The output can be filtered to display information only for the exit ID (OER assigns an ID number to each exit interface) or for the specified border router. The current keyword displays traceroute probe results from the most recent traceroute probe. The now keyword initiates a new traceroute probe and displays the results.
Examples
The following example shows the status of a monitored prefix:
Router# show oer master prefixOER Prefix Stats:Dly: Delay in msEBw: Egress BandwidthIBw: Ingress BandwidthPrefix State Curr BR CurrI/F Dly EBw IBw----------------------------------------------------------10.1.5.0/24 INPOLICY 10.1.1.2 Et1/0 19 1 1Table 1 describes the significant fields shown in the display.
The following output shows the detailed status of a monitored prefix:
Router# show oer master prefix detailPrefix: 10.1.1.0/26State: DEFAULT* Time Remaining: @7Policy: DefaultMost recent data per exitBorder Interface PasSDly PasLDly ActSDly ActLDly*10.2.1.1 Et1/0 181 181 250 25010.2.1.2 Et2/0 0 0 351 35110.3.1.2 Et3/0 0 0 94 943Latest Active Stats on Current Exit:Type Target TPort Attem Comps DSum Min Max Dlyecho 10.1.1.1 N 2 2 448 208 240 224echo 10.1.1.2 N 2 2 488 228 260 244echo 10.1.1.3 N 2 2 568 268 300 284Prefix performance history recordsCurrent index 2, S_avg interval(min) 5, L_avg interval(min) 60Age Border Interface OOP/RteChg ReasonsPas: DSum Samples DAvg PktLoss Unreach Ebytes Ibytes Pkts FlowsAct: Dsum Attempts DAvg Comps Unreach00:00:03 10.1.1.1 Et1/00 0 0 0 0 0 0 0 01504 6 250 6 0Table 2 describes the significant fields shown in the display.
The following example shows prefix statistics from a traceroute probing:
Router# show oer master prefix 10.1.5.0/24 traceroute* - current exit, + - control more specificEx - Exit ID, Delay in msec--------------------------------------------------------------------------------Path for Prefix: 10.1.5.0/24 Target: 10.1.5.2Exit ID: 2, Border: 10.1.1.3 External Interface: Et1/0Status: DONE, How Recent: 00:00:08 minutes oldHop Host Time(ms) BGP1 10.1.4.2 8 02 10.1.3.2 8 3003 10.1.5.2 20 50--------------------------------------------------------------------------------Exit ID: 1, Border: 10.1.1.2 External Interface: Et1/0Status: DONE, How Recent: 00:00:06 minutes oldHop Host Time(ms) BGP1 0.0.0.0 3012 02 10.1.3.2 12 1003 10.1.5.2 12 50--------------------------------------------------------------------------------Table 3 describes the significant fields shown in the display.
The following example shows prefix statistics including Jitter and MOS percentage values when the Jitter probe is configured for the 10.1.5.0 prefix:
Router# show oer master prefix 10.1.5.0/24OER Prefix Statistics:Pas - Passive, Act - Active, S - Short term, L - Long term, Dly - Delay (ms),P - Percentage below threshold, Jit - Jitter, MOS - Mean Opinion Score,Los - Packet Loss (packets-per-million), Un - Unreachable (flows-per-million),E - Egress, I - Ingress, Bw - Bandwidth (kbps), N - Not applicableU - unknown, * - uncontrolled, + - control more specific, @ - active probe allPrefix State Time Curr BR CurrI/F ProtocolPasSDly PasLDly PasSUn PasLUn PasSLos PasLLosActSDly ActLDly ActSUn ActLUn EBw IBw%ActSJit %ActPMOS--------------------------------------------------------------------------------10.1.1.0/24 DEFAULT* @3 10.1.1.1 Et5/0 UU U 0 0 0 06 6 400000 400000 17 11.45 25Table 4 describes the significant fields shown in the display that are different from Table 1 and Table 2.
The following example shows detailed prefix statistics when Jitter or MOS are configured as a priority:
Router# show oer master prefix 10.1.1.0/24 detailPrefix: 10.1.1.0/24State: DEFAULT* Time Remaining: @9Policy: DefaultMost recent data per exitBorder Interface PasSDly PasLDly ActSDly ActLDly*10.1.1.1 Et5/0 0 0 6 610.2.2.3 Et2/0 0 0 7 710.1.1.2 Et0/0 0 0 14 14Most recent voice data per exitBorder Interface ActSJit ActPMOS*10.1.1.1 Et5/0 2.00 010.2.2.3 Et2/0 2.01 2010.1.1.2 Et0/0 4.56 50Latest Active Stats on Current Exit:Type Target TPort Attem Comps DSum Min Max DlyudpJit 10.1.1.8 2000 2 2 8 4 4 4udpJit 10.1.1.7 3000 2 2 20 4 16 10udpJit 10.1.1.6 4000 2 2 8 4 4 4echo 10.1.1.4 N 2 0 0 0 0 0echo 10.1.1.3 N 2 0 0 0 0 0Latest Voice Stats on Current Exit:Type Target TPort Codec Attem Comps JitSum MOSudpJit 10.1.1.8 2000 g711alaw 2 2 2.34 4.56udpJit 10.1.1.7 3000 g711ulaw 2 2 2.56 4.11udpJit 10.1.1.6 4000 g729a 2 2 1.54 3.57udpJit 10.1.1.5 4500 none 2 2 1.76 NAPrefix performance history recordsCurrent index 3, S_avg interval(min) 5, L_avg interval(min) 60Age Border Interface OOP/RteChg ReasonsPas: DSum Samples DAvg PktLoss Unreach Ebytes Ibytes Pkts FlowsAct: Dsum Attempts DAvg Comps Unreach Jitter LoMOSCnt MOSCn00:00:07 10.1.1.1 Et5/00 0 0 0 0 5920 0 148 136 10 6 6 4 2 1 100:01:07 10.1.1.1 Et5/00 0 0 0 0 12000 12384 606 1636 10 6 6 4 3 0 100:02:07 10.1.1.1 Et5/00 0 0 0 0 409540 12040 867 936 10 6 6 4 15 1 1Table 5 describes the significant fields shown in the display that are different from Table 2.
Related Commands
Feature Information for OER BGP Inbound Optimization
Table 6 lists the release history for this feature.
For information on a feature in this technology that is not documented here, see the "Cisco IOS Optimized Edge Routing Feature Roadmap."
Not all commands may be available in your Cisco IOS software release. For release information about a specific command, see the command reference documentation.
Cisco IOS software images are specific to a Cisco IOS software release, a feature set, and a platform. Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at the login dialog box and follow the instructions that appear.
Note
Table 6 Feature Information for OER BGP Inbound Optimization
OER BGP Inbound Optimization
12.4(9)T
OER BGP inbound optimization supports best entrance selection for traffic that originates from prefixes outside an autonomous system destined for prefixes inside the autonomous system. External BGP (eBGP) advertisements from an autonomous system to an Internet service provider (ISP) can influence the entrance path for traffic entering the network. OER uses eBGP advertisements to manipulate the best entrance selection.
The following sections provide information about this feature:
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The following commands were introduced or modified by this feature: clear oer master prefix, inside bgp, match ip address (OER), match oer learn, show oer master prefix.
Any Internet Protocol (IP) addresses used in this document are not intended to be actual addresses. Any examples, command display output, and figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses in illustrative content is unintentional and coincidental.
© 2006 Cisco Systems, Inc. All rights reserved.
