- Finding Feature Information
- Prerequisites for Invalid Security Parameter Index Recovery
- Restrictions for Invalid Security Parameter Index Recovery
- Information About Invalid Security Parameter Index Recovery
- How to Configure Invalid Security Parameter Index Recovery
- Configuration Examples for Invalid Security Parameter Index Recovery
- Additional References
- Feature Information for Invalid Security Parameter Index Recovery
Invalid Security Parameter Index Recovery
When an invalid security parameter index error (shown as “Invalid SPI”) occurs in IP Security (IPsec) packet processing, the Invalid Security Parameter Index Recovery feature allows for an Internet Key Exchange (IKE) security association (SA) to be established. The “IKE” module sends notification of the “Invalid SPI” error to the originating IPsec peer so that Security Association Databases (SADBs) can be resynchronized and successful packet processing can be resumed.
- Finding Feature Information
- Prerequisites for Invalid Security Parameter Index Recovery
- Restrictions for Invalid Security Parameter Index Recovery
- Information About Invalid Security Parameter Index Recovery
- How to Configure Invalid Security Parameter Index Recovery
- Configuration Examples for Invalid Security Parameter Index Recovery
- Additional References
- Feature Information for Invalid Security Parameter Index Recovery
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Prerequisites for Invalid Security Parameter Index Recovery
Before configuring the Invalid Security Parameter Index Recovery feature, you must have enabled Internet Key Exchange (IKE) and IPsec on your router.
Restrictions for Invalid Security Parameter Index Recovery
If an IKE SA is being initiated to notify an IPsec peer of an “Invalid SPI” error, there is the risk that a denial-of-service (DoS) attack can occur. The Invalid Security Parameter Index Recovery feature has a built-in mechanism to minimize such a risk, but because there is a risk, the Invalid Security Parameter Index Recovery feature is not enabled by default. You must enable the command using command-line interface (CLI).
Information About Invalid Security Parameter Index Recovery
How the Invalid Security Parameter Index Recovery Feature Works
An IPsec “black hole” occurs when one IPsec peer “dies” (for example, a peer can “die” if a reboot occurs or if an IPsec peer somehow gets reset). Because one of the peers (the receiving peer) is completely reset, it loses its IKE SA with the other peer. Generally, when an IPsec peer receives a packet for which it cannot find an SA, it tries to send an IKE “INVALID SPI NOTIFY” message to the data originator. This notification is sent using the IKE SA. If there is no IKE SA available, the receiving peer drops the packet.
 Note |
A single security association (SA) has only two peers. However, a SADB can have multiple SAs, whereby each SA has an association with a different peer. |
When an invalid security parameter index (SPI) is encountered, the Invalid Security Parameter Index feature provides for the setting up of an IKE SA with the originator of the data, and the IKE “INVALID SPI NOTIFY” message is sent. The peer that originated the data “sees” the “INVALID SPI NOTIFY” message and deletes the IPsec SA that has the invalid SPI. If there is further traffic from the originating peer, there will not be any IPsec SAs, and new SAs will be set up. Traffic will flow again. The default behavior (that is, without configuring the Invalid Security Parameter Index Recovery feature) is that the data packet that caused the invalid SPI error is dropped. The originating peer keeps on sending the data using the IPsec SA that has the invalid SPI, and the receiving peer keeps dropping the traffic (thus creating the “black hole”).
The IPsec module uses the IKE module to send an IKE “INVALID SPI NOTIFY” message to the other peer. Once the invalid SPI recovery is in place, there should not be any significant dropping of packets although the IPsec SA setup can itself result in the dropping of a few packets.
To configure your router for the Invalid Security Parameter Index Recovery feature, use the crypto isakmp invalid-spi-recovery command. The IKE SA will not be initiated unless you have configured this command.
How to Configure Invalid Security Parameter Index Recovery
- Configuring Invalid Security Parameter Index Recovery
- Verifying the Invalid Security Parameter Index Recovery Configuration
Configuring Invalid Security Parameter Index Recovery
To configure the Invalid Security Parameter Index Recovery feature, perform the following steps.
DETAILED STEPS
Verifying the Invalid Security Parameter Index Recovery Configuration
To determine the status of the IPsec SA for traffic between two peers, you can use the show crypto ipsec sa command. If the IPsec SA is available on one peer and not on the other, there is a “black hole” situation, in which case you will see the invalid SPI errors being logged for the receiving peer. If you turn console logging on or check the syslog server, you will see that these errors are also being logged.
The figure below shows the topology of a typical preshared configuration setup. Host 1 is the initiating peer (initiator), and Host 2 is the receiving peer (responder).
| Figure 1 | Preshared Configuration Topology |
DETAILED STEPS
Configuration Examples for Invalid Security Parameter Index Recovery
Invalid Security Parameter Index Recovery Example
The following example shows that invalid security parameter index recovery has been configured on Router A and Router B. Invalid Security Parameter Index Recovery Example shows the topology used for this example.
Router A
Router# show running-config
Building configuration...
Current configuration : 2048 bytes
!
version 12.3
no service pad
service timestamps debug datetime msec localtime
service timestamps log datetime msec localtime
no service password-encryption
service tcp-small-servers
!
hostname ipseca-71a
!
logging queue-limit 100
no logging console
enable secret 5 $1$4GZB$L2YOmnenOCNAu0jgFxebT/
enable password lab
!
clock timezone PST -8
clock summer-time PDT recurring
ip subnet-zero
!
!
no ip domain lookup
!
ip cef
ip audit notify log
ip audit po max-events 100
mpls ldp logging neighbor-changes
no ftp-server write-enable
!
!
no voice hpi capture buffer
no voice hpi capture destination
!
!
crypto isakmp policy 1
authentication pre-share
lifetime 180
crypto isakmp key 0 1234 address 10.2.2.2
crypto isakmp invalid-spi-recovery
!
!
crypto ipsec transform-set auth2 ah-sha-hmac esp-des esp-sha-hmac
!
crypto map testtag1 10 ipsec-isakmp
set peer 10.2.2.2
set transform-set auth2
match address 150
!
!
controller ISA 5/1
!
!
interface FastEthernet0/0
ip address 10.1.1.1 255.0.0.0
no ip route-cache cef
duplex full
speed 100
crypto map testtag1
!
interface FastEthernet0/1
ip address 10.0.0.1 255.0.0.0
no ip route-cache cef
duplex auto
speed auto
!
interface Serial1/0
no ip address
no ip route-cache
no ip mroute-cache
shutdown
serial restart_delay 0
clockrate 128000
!
interface Serial1/1
no ip address
no ip route-cache
no ip mroute-cache
shutdown
serial restart_delay 0
clockrate 128000
!
interface Serial1/2
no ip address
no ip route-cache
no ip mroute-cache
shutdown
serial restart_delay 0
!
interface Serial1/3
no ip address
no ip route-cache
no ip mroute-cache
shutdown
no keepalive
serial restart_delay 0
clockrate 128000
!
ip classless
ip route 10.3.3.3 255.0.0.0 10.2.0.1
no ip http server
no ip http secure-server
!
!
access-list 150 permit ip host 10.0.0.1 host 10.0.2.2
dialer-list 1 protocol ip permit
dialer-list 1 protocol ipx permit
!
!
call rsvp-sync
!
!
mgcp profile default
!
!
line con 0
exec-timeout 0 0
line aux 0
line vty 0 4
password lab
login
!
!
end
ipseca-71a#
Router B
Router# show running-config
Building configuration...
Current configuration : 2849 bytes
!
version 12.3
no service pad
service timestamps debug datetime msec localtime
service timestamps log datetime msec localtime
no service password-encryption
service udp-small-servers
service tcp-small-servers
!
hostname ipseca-72a
!
logging queue-limit 100
no logging console
enable secret 5 $1$kKqL$5Th5Qhw1ubDkkK90KWFxi1
enable password lab
!
clock timezone PST -8
clock summer-time PDT recurring
ip subnet-zero
!
!
no ip domain lookup
!
ip cef
ip audit notify log
ip audit po max-events 100
mpls ldp logging neighbor-changes
no ftp-server write-enable
!
!
no voice hpi capture buffer
no voice hpi capture destination
!
!
mta receive maximum-recipients 0
!
!
crypto isakmp policy 1
authentication pre-share
lifetime 180
crypto isakmp key 0 1234 address 10.1.1.1
crypto isakmp invalid-spi-recovery
!
!
crypto ipsec transform-set auth2 ah-sha-hmac esp-des esp-sha-hmac
!
crypto map testtag1 10 ipsec-isakmp
set peer 10.1.1.1
set transform-set auth2
match address 150
!
!
controller ISA 5/1
!
!
interface FastEthernet0/0
no ip address
no ip route-cache
no ip mroute-cache
shutdown
duplex half
!
interface Ethernet1/0
ip address 10.2.2.2 255.0.0.0
no ip route-cache cef
duplex half
crypto map testtag1
!
interface Ethernet1/1
ip address 10.0.2.2 255.0.0.0
no ip route-cache cef
duplex half
!
interface Ethernet1/2
no ip address
no ip route-cache
no ip mroute-cache
shutdown
duplex half
!
interface Ethernet1/3
no ip address
no ip route-cache
no ip mroute-cache
shutdown
duplex half
!
interface Ethernet1/4
no ip address
no ip route-cache
no ip mroute-cache
shutdown
duplex half
!
interface Ethernet1/5
no ip address
no ip route-cache
no ip mroute-cache
shutdown
duplex half
!
interface Ethernet1/6
no ip address
no ip route-cache
no ip mroute-cache
shutdown
duplex half
!
interface Ethernet1/7
no ip address
no ip route-cache
no ip mroute-cache
shutdown
duplex half
!
interface Serial3/0
no ip address
no ip route-cache
no ip mroute-cache
shutdown
serial restart_delay 0
!
interface Serial3/1
no ip address
no ip route-cache
no ip mroute-cache
shutdown
serial restart_delay 0
clockrate 128000
!
interface Serial3/2
no ip address
no ip route-cache
no ip mroute-cache
shutdown
serial restart_delay 0
!
interface Serial3/3
no ip address
no ip route-cache
no ip mroute-cache
shutdown
no keepalive
serial restart_delay 0
clockrate 128000
!
ip classless
ip route 10.0.0.0 255.0.0.0 10.2.0.1
no ip http server
no ip http secure-server
!
!
access-list 150 permit ip host 10.0.2.2 host 10.0.0.1
dialer-list 1 protocol ip permit
dialer-list 1 protocol ipx permit
!
!
call rsvp-sync
!
!
mgcp profile default
!
dial-peer cor custom
!
!
gatekeeper
shutdown
!
!
line con 0
exec-timeout 0 0
stopbits 1
line aux 0
stopbits 1
line vty 0 4
password lab
login
!
!
end
Additional References
Related Documents
| Related Topic |
Document Title |
|---|---|
| Configuring IKE |
Configuring Internet Key Exchange for IPsec VPNs |
| Interface commands |
MIBs
| MIBs |
MIBs Link |
|---|---|
| None. |
To locate and download MIBs for selected platforms, Cisco IOS software releases, and feature sets, use Cisco MIB Locator found at the following URL: |
Technical Assistance
| Description |
Link |
|---|---|
| The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. |
Feature Information for Invalid Security Parameter Index Recovery
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
| Table 1 | Feature Information for Invalid Security Parameter Index Recovery |
| Feature Name |
Releases |
Feature Information |
|---|---|---|
| Invalid Security Parameter Index Recovery |
12.3(2)T 12.2(18)SXE |
When an invalid security parameter index error (shown as “Invalid SPI”) occurs in IP Security (IPsec) packet processing, the Invalid Security Parameter Index Recovery feature allows for an Internet Key Exchange (IKE) security association (SA) to be established. The “IKE” module sends notification of the “Invalid SPI” error to the originating IPsec peer so that Security Association Databases (SADBs) can be resynchronized and successful packet processing can be resumed. This feature was introduced in Cisco IOS Release 12.3(2)T. This feature was integrated into Cisco IOS Release 12.2(18)SXE. The following command was introduced or modified: crypto isakmp invalid-spi-recovery |
Cisco and the Cisco Logo are trademarks of Cisco Systems, Inc. and/or its affiliates in the U.S. and other countries. A listing of Cisco's trademarks can be found at www.cisco.com/go/trademarks. Third party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1005R)
Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.
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