Document ID: 3969
Updated: Apr 04, 2008
Contents
Introduction
This document describes how to configure generic routing encapsulation (GRE) over IPSec between a Cisco VPN 5000 Series Concentrator and a Cisco router running Cisco IOS® software. The GRE-over-IPSec feature is introduced in the VPN 5000 Concentrator 6.0(19) software release.
In this example, static routing is used to route packets across the tunnel.
Prerequisites
Requirements
There are no specific requirements for this document.
Components Used
The information in this document is based on these software and hardware versions:
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Cisco IOS Software Release 12.2(3)
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Cisco VPN 5000 Concentrator software version 6.0(19)
The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.
Conventions
For more information on document conventions, refer to the Cisco Technical Tips Conventions.
Configure
In this section, you are presented with the information to configure the features described in this document.
Note: To find additional information on the commands used in this document, use the Command Lookup Tool (registered customers only) .
Network Diagram
This document uses the network setup shown in this diagram.
GRE over IPSec is configured between the 1720-1 router running Cisco IOS software and the VPN 5002 Concentrator. Behind the router and the VPN Concentrator, there are multiple networks that are advertised through Open Shortest Path First (OSPF). OSPF runs within the GRE tunnel between the router and the VPN Concentrator.
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These networks are behind the 1720-1 router.
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10.1.1.0/24
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10.1.2.0/24
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10.1.3.0/24
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These networks are behind the VPN 5002 Concentrator.
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20.1.1.0/24
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20.1.2.0/24
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20.1.3.0/24
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Configurations
This document uses these configurations.
Note: With Cisco IOS Software Releases 12.2(13)T and later (higher numbered T-train codes, 12.3 and later codes), you must apply the configured IPSec crypto map to the physical interface only. You no longer have to apply the crypto map on the GRE tunnel interface. Having the crypto map on the physical and the tunnel interfaces when you use Cisco IOS Software Releases 12.2.(13)T and later should still work, but Cisco Systems recommends that you apply the crypto map on the physical interface only.
| 1720-1 Router |
|---|
Current configuration : 1305 bytes ! version 12.2 service timestamps debug uptime service timestamps log uptime no service password-encryption ! hostname 1720-1 ! no logging buffered no logging monitor enable secret 5 $1$vIzI$RqD0LqlqbSFCCjVELFLfH/ ! memory-size iomem 15 ip subnet-zero no ip domain-lookup ! ip audit notify log ip audit po max-events 100 ip ssh time-out 120 ip ssh authentication-retries 3 ! crypto isakmp policy 1 hash md5 authentication pre-share crypto isakmp key cisco123 address 172.16.172.21 ! ! crypto ipsec transform-set myset esp-des esp-md5-hmac mode transport ! crypto map vpn 10 ipsec-isakmp set peer 172.16.172.21 set transform-set myset match address 102 ! cns event-service server ! ! ! interface Tunnel0 ip address 50.1.1.1 255.255.255.252 tunnel source FastEthernet0 tunnel destination 172.16.172.21 crypto map vpn ! interface FastEthernet0 ip address 172.16.172.39 255.255.255.240 speed auto crypto map vpn ! interface Serial0 ip address 10.1.1.2 255.255.255.0 encapsulation ppp ! ip classless ip route 0.0.0.0 0.0.0.0 172.16.172.33 ip route 10.1.0.0 255.255.0.0 10.1.1.1 ip route 20.1.0.0 255.255.0.0 Tunnel0 no ip http server ! access-list 102 permit gre host 172.16.172.39 host 172.16.172.21 ! line con 0 line aux 0 line vty 0 4 password cisco login ! no scheduler allocate end |
| VPN 5002 Concentrator |
|---|
[ General ] VPNGateway = 172.16.172.17 EthernetAddress = 00:05:32:3e:90:40 DeviceType = VPN 5002/8 Concentrator ConfiguredOn = Timeserver not configured ConfiguredFrom = Command Line, from Console [ IKE Policy ] Protection = SHA_DES_G1 Protection = MD5_DES_G2 Protection = MD5_DES_G1 [ Tunnel Partner VPN 1 ] KeyLifeSecs = 3500 KeepaliveInterval = 120 TunnelType = GREinIPSec InactivityTimeout = 120 Transform = ESP(MD5,DES) BindTo = "Ethernet 1:0" SharedKey = "cisco123" Certificates = Off Mode = Main KeyManage = Reliable Partner = 172.16.172.39 [ IP VPN 1 ] HelloInterval = 10 SubnetMask = 255.255.255.252 IPAddress = 50.1.1.2 DirectedBroadcast = Off Numbered = On Mode = Routed [ IP Ethernet 1:0 ] Mode = Routed SubnetMask = 255.255.255.240 IPBroadcast = 172.16.172.32 IPAddress = 172.16.172.21 [ IP Ethernet 0:0 ] Mode = Routed IPBroadcast = 20.1.1.255 SubnetMask = 255.255.255.0 IPAddress = 20.1.1.1 [ Logging ] Level = Debug LogToAuxPort = On Enabled = On [ Ethernet Interface Ethernet 0:0 ] DUPLEX = half SPEED = 10meg [ IP Static ] 0.0.0.0 0.0.0.0 20.1.1.5 1 10.1.1.0 255.255.255.0 VPN 1 1 10.1.2.0 255.255.255.0 VPN 1 1 10.1.3.0 255.255.255.0 VPN 1 1 Configuration size is 1696 out of 65500 bytes. |
Verify
This section provides information you can use to confirm your configuration is working properly.
Certain show commands are supported by the Output Interpreter Tool (registered customers only) , which allows you to view an analysis of show command output.
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These commands can be run on the Cisco IOS router.
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show crypto isakmp sa—Shows all current Internet Security Association and Key Management Protocol (ISAKMP) security associations (SAs).
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show crypto ipsec sa—Shows all current IPSec SAs.
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show crypto engine connection active—Shows packet encryption/decryption counter for each IPSec SAs.
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You can run these commands on the VPN 5002 Concentrator.
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show system log buffer—Shows basic syslog information.
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vpn trace dump—Shows detailed information about VPN processes.
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Troubleshoot
This section provides information you can use to troubleshoot your configuration.
Troubleshooting Commands
Note: Before issuing debug commands, please see Important Information on Debug Commands.
You can run these commands on the Cisco IOS router.
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debug crypto isakmp—Shows detailed information about Internet Key Exchange (IKE) phase I (Main Mode) negotiation.
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debug crypto ipsec—Shows detailed information about IKE phase II (Quick Mode) negotiation.
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debug crypto engine—Debugs packet encryption/decryption and Diffie-Hellman (DH) process.
Sample debug Output
Sample debug output for the router and VPN Concentrator is shown here.
Debugs on the Cisco IOS Router
Output of debug crypto isakmp and debug crypto ipsec commands on the router is shown here.
5d20h: ISAKMP (0:0): received packet from 172.16.172.21 (N) NEW SA
5d20h: ISAKMP: local port 500, remote port 500
5d20h: ISAKMP (0:81): processing SA payload. message ID = 0
5d20h: ISAKMP (0:81): found peer pre-shared key matching 172.16.172.21
5d20h: ISAKMP (0:81): Checking ISAKMP transform 1 against priority 1 policy
5d20h: ISAKMP: encryption DES-CBC
5d20h: ISAKMP: hash SHA
5d20h: ISAKMP: auth pre-share
5d20h: ISAKMP: default group 1
5d20h: ISAKMP (0:81): atts are not acceptable. Next payload is 3
5d20h: ISAKMP (0:81): Checking ISAKMP transform 2 against priority 1 policy
5d20h: ISAKMP: encryption DES-CBC
5d20h: ISAKMP: hash MD5
5d20h: ISAKMP: auth pre-share
5d20h: ISAKMP: default group 2
5d20h: ISAKMP (0:81): atts are not acceptable. Next payload is 3
5d20h: ISAKMP (0:81): Checking ISAKMP transform 3 against priority 1 policy
5d20h: ISAKMP: encryption DES-CBC
5d20h: ISAKMP: hash MD5
5d20h: ISAKMP: auth pre-share
5d20h: ISAKMP: default group 1
5d20h: ISAKMP (0:81): atts are acceptable. Next payload is 0
5d20h: ISAKMP (0:81): processing vendor id payload
5d20h: ISAKMP (0:81): SA is doing pre-shared key authentication
using id type ID_IPV4_ADDR
5d20h: ISAKMP (0:81): sending packet to 172.16.172.21 (R) MM_SA_SETUP
5d20h: ISAKMP (0:81): received packet from 172.16.172.21 (R) MM_SA_SETUP
5d20h: ISAKMP (0:81): processing KE payload. message ID = 0
5d20h: ISAKMP (0:81): processing NONCE payload. message ID = 0
5d20h: ISAKMP (0:81): found peer pre-shared key matching 172.16.172.21
5d20h: ISAKMP (0:81): SKEYID state generated
5d20h: ISAKMP (0:81): sending packet to 172.16.172.21 (R) MM_KEY_EXCH
5d20h: ISAKMP (0:81): received packet from 172.16.172.21 (R) MM_KEY_EXCH
5d20h: ISAKMP (0:81): processing ID payload. message ID = 0
5d20h: ISAKMP (0:81): processing HASH payload. message ID = 0
5d20h: ISAKMP (0:81): SA has been authenticated with 172.16.172.21
5d20h: ISAKMP (81): ID payload
next-payload : 8
type : 1
protocol : 17
port : 500
length : 8
5d20h: ISAKMP (81): Total payload length: 12
5d20h: ISAKMP (0:81): sending packet to 172.16.172.21 (R) QM_IDLE
5d20h: ISAKMP (0:81): received packet from 172.16.172.21 (R) QM_IDLE
5d20h: ISAKMP (0:81): processing HASH payload. message ID = 241
5d20h: ISAKMP (0:81): processing SA payload. message ID = 241
5d20h: ISAKMP (0:81): Checking IPSec proposal 1
5d20h: ISAKMP: transform 1, ESP_DES
5d20h: ISAKMP: attributes in transform:
5d20h: ISAKMP: SA life type in seconds
5d20h: ISAKMP: SA life duration (VPI) of 0x0 0x0 0xD 0xAC
5d20h: ISAKMP: SA life type in kilobytes
5d20h: ISAKMP: SA life duration (VPI) of 0x0 0x10 0x0 0x0
5d20h: ISAKMP: encaps is 2
5d20h: ISAKMP: authenticator is HMAC-MD5
5d20h: ISAKMP (0:81): atts are acceptable.
5d20h: IPSEC(validate_proposal_request): proposal part #1,
(key eng. msg.) dest= 172.16.172.39, src= 172.16.172.21,
dest_proxy= 172.16.172.39/255.255.255.255/47/0 (type=1),
src_proxy= 172.16.172.21/255.255.255.255/47/0 (type=1),
protocol= ESP, transform= esp-des esp-md5-hmac ,
lifedur= 0s and 0kb,
spi= 0x0(0), conn_id= 0, keysize= 0, flags= 0x0
5d20h: ISAKMP (0:81): processing NONCE payload. message ID = 241
5d20h: ISAKMP (0:81): processing ID payload. message ID = 241
5d20h: ISAKMP (81): ID_IPV4_ADDR src 172.16.172.21 prot 47 port 0
5d20h: ISAKMP (0:81): processing ID payload. message ID = 241
5d20h: ISAKMP (81): ID_IPV4_ADDR dst 172.16.172.39 prot 47 port 0
5d20h: ISAKMP (0:81): asking for 1 spis from ipsec
5d20h: IPSEC(key_engine): got a queue event...
5d20h: IPSEC(spi_response): getting spi 895566248 for SA
from 172.16.172.21 to 172.16.172.39 for prot 3
5d20h: ISAKMP: received ke message (2/1)
5d20h: ISAKMP (0:81): sending packet to 172.16.172.21 (R) QM_IDLE
5d20h: ISAKMP (0:81): received packet from 172.16.172.21 (R) QM_IDLE
5d20h: ISAKMP (0:81): Creating IPSec SAs
5d20h: inbound SA from 172.16.172.21 to 172.16.172.39
(proxy 172.16.172.21 to 172.16.172.39)
5d20h: has spi 0x356141A8 and conn_id 362 and flags 0
5d20h: lifetime of 3500 seconds
5d20h: lifetime of 1048576 kilobytes
5d20h: outbound SA from 172.16.172.39 to 172.16.172.21
(proxy 172.16.172.39 to 172.16.172.21 )
5d20h: has spi 337 and conn_id 363 and flags 0
5d20h: lifetime of 3500 seconds
5d20h: lifetime of 1048576 kilobytes
5d20h: ISAKMP (0:81): deleting node 241 error FALSE reason
"quick mode done (await()"
5d20h: IPSEC(key_engine): got a queue event...
5d20h: IPSEC(initialize_sas): ,
(key eng. msg.) dest= 172.16.172.39, src= 172.16.172.21,
dest_proxy= 172.16.172.39/0.0.0.0/47/0 (type=1),
src_proxy= 172.16.172.21/0.0.0.0/47/0 (type=1),
protocol= ESP, transform= esp-des esp-md5-hmac ,
lifedur= 3500s and 1048576kb,
spi= 0x356141A8(895566248), conn_id= 362, keysize= 0, flags= 0x0
5d20h: IPSEC(initialize_sas): ,
(key eng. msg.) src= 172.16.172.39, dest= 172.16.172.21,
src_proxy= 172.16.172.39/0.0.0.0/47/0 (type=1),
dest_proxy= 172.16.172.21/0.0.0.0/47/0 (type=1),
protocol= ESP, transform= esp-des esp-md5-hmac ,
lifedur= 3500s and 1048576kb,
spi= 0x151(337), conn_id= 363, keysize= 0, flags= 0x0
5d20h: IPSEC(create_sa): sa created,
(sa) sa_dest= 172.16.172.39, sa_prot= 50,
sa_spi= 0x356141A8(895566248),
sa_trans= esp-des esp-md5-hmac , sa_conn_id= 362
5d20h: IPSEC(create_sa): sa created,
(sa) sa_dest= 172.16.172.21, sa_prot= 50,
sa_spi= 0x151(337),
sa_trans= esp-des esp-md5-hmac , sa_conn_id= 363
5d20h: IPSEC(add_sa): peer asks for new SAs -- expire current in 120 sec.,
(sa) sa_dest= 172.16.172.21, sa_prot= 50,
sa_spi= 0x150(336),
sa_trans= esp-des esp-md5-hmac , sa_conn_id= 361,
(identity) local= 172.16.172.39, remote= 172.16.172.21,
local_proxy= 172.16.172.39/255.255.255.255/47/0 (type=1),
remote_proxy= 172.16.172.21/255.255.255.255/47/0 (type=1)
1720-1#
1720-1#show crypto isakmp sa
dst src state conn-id slot
172.16.172.39 172.16.172.21 QM_IDLE 81 0
1720-1#show crypto ipsec sa
interface: FastEthernet0
Crypto map tag: vpn, local addr. 172.16.172.39
local ident (addr/mask/prot/port): (172.16.172.39/255.255.255.255/0/0)
remote ident (addr/mask/prot/port): (172.16.172.21/255.255.255.255/0/0)
current_peer: 172.16.172.21
PERMIT, flags={transport_parent,}
#pkts encaps: 0, #pkts encrypt: 0, #pkts digest 0
#pkts decaps: 0, #pkts decrypt: 0, #pkts verify 0
#pkts compressed: 0, #pkts decompressed: 0
#pkts not compressed: 0, #pkts compr. failed: 0,
#pkts decompress failed: 0, #send errors 0, #recv errors 0
local crypto endpt.: 172.16.172.39, remote crypto endpt.: 172.16.172.21
path mtu 1514, media mtu 1514
current outbound spi: 0
inbound esp sas:
inbound ah sas:
inbound pcp sas:
outbound esp sas:
outbound ah sas:
outbound pcp sas:
local ident (addr/mask/prot/port): (172.16.172.39/255.255.255.255/47/0)
remote ident (addr/mask/prot/port): (172.16.172.21/255.255.255.255/47/0)
current_peer: 172.16.172.21
PERMIT, flags={origin_is_acl,transport_parent,parent_is_transport,}
#pkts encaps: 34901, #pkts encrypt: 34901, #pkts digest 34901
#pkts decaps: 34900, #pkts decrypt: 34900, #pkts verify 34900
#pkts compressed: 0, #pkts decompressed: 0
#pkts not compressed: 0, #pkts compr. failed: 0,
#pkts decompress failed: 0, #send errors 0, #recv errors 0
local crypto endpt.: 172.16.172.39, remote crypto endpt.: 172.16.172.21
path mtu 1500, media mtu 1500
current outbound spi: 151
inbound esp sas:
spi: 0x356141A8(895566248)
transform: esp-des esp-md5-hmac ,
in use settings ={Transport, }
slot: 0, conn id: 362, flow_id: 163, crypto map: vpn
sa timing: remaining key lifetime (k/sec): (1046258/3306)
IV size: 8 bytes
replay detection support: Y
inbound ah sas:
inbound pcp sas:
outbound esp sas:
spi: 0x151(337)
transform: esp-des esp-md5-hmac ,
in use settings ={Transport, }
slot: 0, conn id: 363, flow_id: 164, crypto map: vpn
sa timing: remaining key lifetime (k/sec): (1046258/3306)
IV size: 8 bytes
replay detection support: Y
outbound ah sas:
outbound pcp sas:
interface: Tunnel0
Crypto map tag: vpn, local addr. 172.16.172.39
local ident (addr/mask/prot/port): (172.16.172.39/255.255.255.255/0/0)
remote ident (addr/mask/prot/port): (172.16.172.21/255.255.255.255/0/0)
current_peer: 172.16.172.21
PERMIT, flags={transport_parent,}
#pkts encaps: 0, #pkts encrypt: 0, #pkts digest 0
#pkts decaps: 0, #pkts decrypt: 0, #pkts verify 0
#pkts compressed: 0, #pkts decompressed: 0
#pkts not compressed: 0, #pkts compr. failed: 0,
#pkts decompress failed: 0, #send errors 0, #recv errors 0
local crypto endpt.: 172.16.172.39, remote crypto endpt.: 172.16.172.21
path mtu 1514, media mtu 1514
current outbound spi: 0
inbound esp sas:
inbound ah sas:
inbound pcp sas:
outbound esp sas:
outbound ah sas:
outbound pcp sas:
local ident (addr/mask/prot/port): (172.16.172.39/255.255.255.255/47/0)
remote ident (addr/mask/prot/port): (172.16.172.21/255.255.255.255/47/0)
current_peer: 172.16.172.21
PERMIT, flags={origin_is_acl,transport_parent,parent_is_transport,}
#pkts encaps: 35657, #pkts encrypt: 35657, #pkts digest 35657
#pkts decaps: 35656, #pkts decrypt: 35656, #pkts verify 35656
#pkts compressed: 0, #pkts decompressed: 0
#pkts not compressed: 0, #pkts compr. failed: 0,
#pkts decompress failed: 0, #send errors 0, #recv errors 0
local crypto endpt.: 172.16.172.39, remote crypto endpt.: 172.16.172.21
path mtu 1500, media mtu 1500
current outbound spi: 151
inbound esp sas:
spi: 0x356141A8(895566248)
transform: esp-des esp-md5-hmac ,
in use settings ={Transport, }
slot: 0, conn id: 362, flow_id: 163, crypto map: vpn
sa timing: remaining key lifetime (k/sec): (1046154/3302)
IV size: 8 bytes
replay detection support: Y
inbound ah sas:
inbound pcp sas:
outbound esp sas:
spi: 0x151(337)
transform: esp-des esp-md5-hmac ,
in use settings ={Transport, }
slot: 0, conn id: 363, flow_id: 164, crypto map: vpn
sa timing: remaining key lifetime (k/sec): (1046154/3302)
IV size: 8 bytes
replay detection support: Y
outbound ah sas:
outbound pcp sas:
1720-1#show crypto engine connections active
ID Interface IP-Address State Algorithm Encrypt Decrypt
81 FastEthernet0 172.16.172.39 set HMAC_MD5+DES_56_CB 0 0
362 FastEthernet0 172.16.172.39 set HMAC_MD5+DES_56_CB 0 23194
363 FastEthernet0 172.16.172.39 set HMAC_MD5+DES_56_CB 23195 0
Debugs on the VPN 5002 Concentrator
Syslog output on the VPN Concentrator is shown here.
VPN5002_8_323E9040: Main# VPN 0:1 opened for 172.16.172.39 from 172.16.172.39.
User assigned IP address 50.1.1.2
VPN5002_8_323E9040: Main#show vpn partner verbose
Port Partner Partner Default Bindto Connect
Number Address Port Partner Address Time
--------------------------------------------------------------------------
VPN 0:1 172.16.172.39 500 No 172.16.172.21 00:00:13:26
Auth/Encrypt: MD5e/DES User Auth: Shared Key
Access: Static Peer: 172.16.172.39 Local: 172.16.172.21
Start:14518 seconds Managed:15299 seconds State:imnt_maintenance
IOP slot 1:
No active connections found.
VPN5002_8_323E9040: Main#show vpn statistics verbose
Current In High Running Script Script Script
Active Negot Water Total Starts OK Error
--------------------------------------------------------------
Users 0 0 0 0 0 0 0
Partners 1 0 1 81 81 1 158
Total 1 0 1 81 81 1 158
Stats VPN0:1
Wrapped 79733
Unwrapped 79734
BadEncap 0
BadAuth 0
BadEncrypt 0
rx IP 79749
rx IPX 0
rx Other 0
tx IP 79761
tx IPX 0
tx Other 0
IKE rekey 0
Input VPN pkts dropped due to no SA: 0
Input VPN pkts dropped due to no free queue entries: 0
IOP slot 1:
Current In High Running Script Script Script
Active Negot Water Total Starts OK Error
--------------------------------------------------------------
Users 0 0 0 0 0 0 0
Partners 0 0 0 0 0 0 0
Total 0 0 0 0 0 0 0
Stats
Wrapped
Unwrapped
BadEncap
BadAuth
BadEncrypt
rx IP
rx IPX
rx Other
tx IP
tx IPX
tx Other
IKE rekey
Input VPN pkts dropped due to no SA: 0
Input VPN pkts dropped due to no free queue entries: 0
Misconfiguration of Tunnel Mode
The VPN 5000 Concentrator proposes transport mode by default when GRE over IPSec is used. When the Cisco IOS router is misconfigured for tunnel mode, then this errors occur.
Debug output on the Cisco IOS router is shown here.
2d21h: ISAKMP (0:23): Checking IPSec proposal 1 2d21h: ISAKMP: transform 1, ESP_DES 2d21h: ISAKMP: attributes in transform: 2d21h: ISAKMP: SA life type in seconds 2d21h: ISAKMP: SA life duration (VPI) of 0x0 0x1 0x51 0x80 2d21h: ISAKMP: SA life type in kilobytes 2d21h: ISAKMP: SA life duration (VPI) of 0x0 0x10 0x0 0x0 2d21h: ISAKMP: encaps is 2 2d21h: ISAKMP: authenticator is HMAC-MD5 2d21h: IPSEC(validate_proposal): invalid transform proposal flags -- 0x0
The log on the VPN 5002 Concentrator shows an entry similar to this output.
lan-lan-VPN0:1:[172.16.172.39]: received notify from partner -- notify: NO PROPOSAL CHOSEN
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Refer to Cisco Technical Tips Conventions for information on conventions used in this document.