Configuration Guide
Configuring QoS for Encrypted Traffic with IPsec
Figure 1
Network Diagram
Introduction
This document describes how to configure Quality of Service (QoS) for encrypted traffic. All encrypted traffic sent from the Hub router (Cisco 7200 Series Router) and a spoke router (Cisco 3745 Series Router) receives an output QoS service policy. The QoS is enabled on the public interface, and it examines the traffic before the traffic is encrypted. The policy is configured using the Modular Quality of Service Command Line Interface (MQC).
Prerequisites
The sample QoS configuration is based on the following assumptions:
Components Used
The sample configuration uses the following releases of the software and hardware:
Figure 1 illustrates the network for the sample configuration.
The information presented in this document was created from devices in a specific lab environment. All of the devices started with a cleared (default) configuration. If you are working in a live network, it is imperative to understand the potential impact of any command before implementing it.
QoS Configuration Options
The sample configuration minimizes bandwidth guarantees and maximizes bandwidth for all IPsec traffic that leaves the routers. Other traffic on the interface can use the bandwidth that IPsec traffic does not use. IPsec traffic can share the rest of the non-reserved bandwidth. Additional QoS features can be used in the policy map: low latency queuing, traffic shaping, and random early detection.
In the sample configuration, the class-map matches all IPsec traffic leaving the routers. The matching for the traffic is made with ACL 122. Additional matching criteria can be made based the on TOS Bits, the IPsec peer source, and the destination address. The TOS bits for the original packet are copied to the outer IPsec encapsulation, enabling the application of different service policies to different classes for the same destination site, as well as support applications such as voice and video.
The service policy could be applied on the input or on the output to the public interface of both routers. The sample configuration shows the service policy applied to output traffic on the hub and the spoke router.
For additional information about configuring QoS, refer to Cisco IOS Quality of Service Solutions Configuration Guide.
Cisco 7200 VPN Router Configuration
Cisco 3745 VPN Router Configuration
Verifying the Results
This section provides information you can use to confirm that your configuration is working properly.
Bandwidth 256 (kbps) Max Threshold 64 (packets)
c3745-20#show policy-map interface fastEthernet 0/1
Class-map: encr-traffic (match-any)
4583480 packets, 2594249680 bytes
30 second offered rate 10558000 bps, drop rate 0 bps
4583480 packets, 2594249680 bytes
Output Queue: Conversation 265
Bandwidth 256 (kbps) Max Threshold 64 (packets)
(pkts matched/bytes matched) 36941/21794950
(depth/total drops/no-buffer drops) 0/0/0
Class-map: class-default (match-any)
6770567 packets, 3498848396 bytes
30 second offered rate 9550000 bps, drop rate 0 bps
permit ip 10.0.149.0 0.0.0.255 10.0.50.0 0.0.0.255 (931215910 matches)
permit esp any any (4826174 matches)
The Access-list 101 show matches for traffic to be encrypted, while the access-list 122 show encrypted traffic that have matched the class-map encr-traffic.
Troubleshooting the Configuration
Certain show commands are supported by the Output Interpreter Tool (registered customers only), which analyzes show command output.
Note: Before issuing debug commands, see Important Information about Debug Commands .
- debug crypto isakmp—Displays errors during Phase 1.
- debug crypto ipsec—Displays errors during Phase 2.
- debug crypto engine—Displays information from the crypto engine.
- debug ip your routing protocol—Displays information about routing transactions of your routing protocol.
- clear crypto connection connection-id [slot | rsm | vip]—Terminates an encrypted session currently in progress. Encrypted sessions normally terminate when the session times out. Use the show crypto cisco connections command to see the connection-id value.
- clear crypto isakmp—Clears the Phase 1 security associations.
- clear crypto sa—Clears the Phase 2 security associations.
Related Information
An Introduction to IP Security (IPsec) Encryption
Configuring IPsec Network Security
Configuring Internet Key Exchange Security Protocol
Command Lookup Tool (registered customers only)
Technical Support - Cisco Systems