- Configuring Internet Key Exchange Version 2 (IKEv2)
- Call Admission Control for IKE
- Certificate to ISAKMP Profile Mapping
- Encrypted Preshared Key
- Fragmentation of IKE Packets
- IKE Responder-Only Mode
- Distinguished Name Based Crypto Maps
- IPsec and Quality of Service
- VRF-Aware IPsec
- IKE: Initiate Aggressive Mode (12.2(8)T FM)
- Configuring Internet Key Exchange for IPsec VPNs
- Finding Feature Information
- Contents
- Prerequisites for Call Admission Control for IKE
- Information About Call Admission Control for IKE
- How to Configure Call Admission Control for IKE
- Configuration Examples for Call Admission Control for IKE
- Additional References
- Feature Information for Call Admission Control for IKE
Call Admission Control for IKE
The Call Admission Control for IKE feature describes the application of Call Admission Control (CAC) to the Internet Key Exchange (IKE) protocol in Cisco IOS software. CAC limits the number of simultaneous IKE and IPsec security associations (SAs) (that is, calls to CAC) that a router can establish.
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 for Call Admission Control for IKE" section.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Contents
•
Prerequisites for Call Admission Control for IKE
•Information About Call Admission Control for IKE
•How to Configure Call Admission Control for IKE
•Configuration Examples for Call Admission Control for IKE
•Feature Information for Call Admission Control for IKE
Prerequisites for Call Admission Control for IKE
•Configure IKE on the router.
Information About Call Admission Control for IKE
IKE Session
There are two ways to limit the number of IKE SAs that a router can establish to or from another router:
•Configure the absolute IKE SA limit by entering the crypto call admission limit command. The router drops new IKE SA requests when the value has been reached.
•Configure the system resource limit by entering the call admission limit command. The router drops new IKE SA requests when the level of system resources that are configured in the unit of charge is being used.
CAC is applied only to new SAs (that is, when an SA does not already exist between the peers). Every effort is made to preserve existing SAs. Only new SA requests will ever be denied due to a lack of system resources or because the configured IKE SA limit has been reached.
Security Association Limit
An SA is a description of how two or more entities will utilize security services to communicate securely on behalf of a particular data flow. IKE requires and uses SAs to identify the parameters of its connections. IKE can negotiate and establish its own SA. An IKE SA is used by IKE only, and it is bidirectional. An IKE SA cannot limit IPsec.
IKE drops SA requests based on a user-configured SA limit. To configure an IKE SA limit, enter the crypto call admission limit command. When there is a new SA request from a peer router, IKE determines whether the number of active IKE SAs plus the number of SAs being negotiated meets or exceeds the configured SA limit. If the number is greater than or equal to the limit, the new SA request is rejected and a syslog is generated. This log contains the source destination IP address of the SA request.
The ipsec sa number and ike sa number keyword and argument pairs in the crypto call admission limit command set the limit for the number of established IPsec SAs and IKE SAs.
Limit on Number of In-Negotiation IKE Connections
Effective with Cisco IOS Release 12.4(6)T, a limit on the number of in-negotiation IKE connections can be configured. This type of IKE connection represents either an aggressive mode IKE SA or a main mode IKE SA prior to its authentication and actual establishment.
Using the crypto call admission limit ike in-negotiation-sa number command allows the configured number of in-negotiation IKE SAs to start negotiation without contributing to the maximum number of IKE SAs allowed.
The all in-negotiation-sa number and ike in-negotiation-sa number keyword and argument pairs in the crypto call admission limit command limit all the SAs in negotiation and IKE SAs in negotiation.
System Resource Usage
CAC polls a global resource monitor so that IKE knows when the router is running short of CPU cycles or memory buffers. You can configure a limit, in the range 1 to 100000, that represents the level of system resource usage in system resource usage units. When that level of resources is being used, IKE drops (will not accept new) SA requests. To configure the system resource usage limit, enter the call admission limit command.
For each incoming new SA request, the current load on the router is converted into a numerical value, representing the system resource usage level, and is compared to the resource limit set by the call admission limit command. If the current load is more than the configured resource limit, IKE drops the new SA request. Load on the router includes active SAs, CPU usage, and SA requests being considered.
The call admission load command configures a multiplier value from 0 to 1000 that represents a scaling factor for current system resource usage and a load metric poll rate of 1 to 32 seconds. The numerical value for the system resource usage level is calculated by the formula (scaling factor * current system resource usage) / 100. It is recommended that the call admission load command not be used unless advised by a Cisco Technical Assistance Center (TAC) engineer.
How to Configure Call Admission Control for IKE
Note You must perform one of the configuration procedures.
•Configuring the IKE Security Association Limit (optional)
•Configuring the System Resource Limit (optional)
•Verifying the Call Admission Control for IKE Configuration (optional)
Configuring the IKE Security Association Limit
Perform this task to configure the absolute IKE SA limit. The router drops new IKE SA requests when the limit has been reached.
SUMMARY STEPS
1. enable
2. configure terminal
3. crypto call admission limit {all in-negotiation-sa number | ipsec sa number | ike {in-negotiation-sa number | sa number}}
4. exit
DETAILED STEPS
Configuring the System Resource Limit
Perform this task to configure the system resource limit. The router drops new IKE SA requests when the level of system resources that are configured in the unit of charge is being used.
SUMMARY STEPS
1. enable
2. configure terminal
3. call admission limit charge
4. exit
DETAILED STEPS
|
|
|
|
|---|---|---|
Step 1 |
enable Router> enable |
Enables privileged EXEC mode. • |
Step 2 |
configure terminal Router# configure terminal |
Enters global configuration mode. |
Step 3 |
call admission limit charge Router(config)# call admission limit 1000 |
Sets the level of the system resources that, when used, causes IKE to stop accepting new SA requests. • Note |
Step 4 |
exit Router(config)# exit |
Exits global configuration mode and returns to privileged EXEC mode. |
Verifying the Call Admission Control for IKE Configuration
To verify the CAC for IKE configuration, perform the following steps.
SUMMARY STEPS
1. show call admission statistics
2. show crypto call admission statistics
DETAILED STEPS
Step 1 show call admission statistics
Use this command to monitor the global CAC configuration parameters and the behavior of CAC.
Router# show call admission statistics
Total Call admission charges: 82, limit 1000
Total calls rejected 1430, accepted 0
Load metric: charge 82, unscaled 82%
Step 2 show crypto call admission statistics
Use this command to monitor crypto CAC statistics.
Router# show crypto call admission statistics
---------------------------------------------------------------------
Crypto Call Admission Control Statistics
---------------------------------------------------------------------
System Resource Limit: 111 Max IKE SAs: 0 Max in nego: 1000
Total IKE SA Count: 0 active: 0 negotiating: 0
Incoming IKE Requests: 0 accepted: 0 rejected: 0
Outgoing IKE Requests: 0 accepted: 0 rejected: 0
Rejected IKE Requests: 0 rsrc low: 0 Active SA limit: 0
In-neg SA limit: 0
IKE packets dropped at dispatch: 0
Max IPSEC SAs: 111
Total IPSEC SA Count: 0 active: 0 negotiating: 0
Incoming IPSEC Requests: 0 accepted: 0 rejected: 0
Outgoing IPSEC Requests: 0 accepted: 0 rejected: 0
Phase1.5 SAs under negotiation: 0
Configuration Examples for Call Admission Control for IKE
This section provides the following configuration examples:
•Example: Configuring the IKE Security Association Limit
•Example: Configuring the System Resource Limit
Example: Configuring the IKE Security Association Limit
The following example shows how to specify a maximum limit of 25 SAs before IKE starts rejecting new SA requests:
Router(config)# crypto call admission limit ike sa 25
Example: Configuring the System Resource Limit
The following example shows how to specify that IKE should drop SA requests when the level of system resources that are configured in the unit of charge reaches 9000:
Router(config)# call admission limit 9000
Additional References
Related Documents
|
|
|
|---|---|
Cisco IOS commands |
|
Configuring IKE |
|
IKE commands |
Standards
|
|
|
|---|---|
None |
— |
MIBs
|
|
|
|---|---|
None |
To locate and download MIBs for selected platforms, Cisco software releases, and feature sets, use Cisco MIB Locator found at the following URL: |
RFCs
|
|
|
|---|---|
RFC 2409 |
The Internet Key Exchange |
Technical Assistance
Feature Information for Call Admission Control for IKE
Table 1 lists the release history for this feature.
Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Note Table 1 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.
|
|
|
|
|---|---|---|
Call Admission Control for IKE |
12.3(8)T |
The Call Admission Control for IKE feature describes the application of Call Admission Control (CAC) to the Internet Key Exchange (IKE) protocol in Cisco IOS software. In Cisco IOS Release 12.3(8)T, this feature was introduced. This feature was integrated into Cisco IOS Release 12.2(18)SXD1 and implemented on the Cisco 6500 and Cisco 7600 routers. In Cisco IOS Release 12.4(6)T, the ability to configure a limit on the number of in-negotiation IKE connections was added. The following sections provide information about this feature: • • The following commands were introduced or modified: call admission limit, clear crypto call admission statistics, crypto call admission limit, show call admission statistics, show crypto call admission statistics. |
IKEv1 Hardening |
15.1(3)T |
The IKEv1 hardening feature describes the enhancements made to the Call Admission Control (CAC) for IKE feature. In Cisco IOS Release 15.1(3)T, this feature was introduced. The following sections provide information about this feature: • • The following commands were introduced or modified: crypto call admission limit, show crypto call admission statistics. |
Feedback