Cisco 500 Series Cache Engines

Configuring IP Spoofing on the Cache Engine in a Transparent Setup with a Content Services Switch

Document ID: 42162

Updated: Sep 01, 2004



This document provides a sample configuration for transparent caching and IP spoofing simultaneously without using Web Cache Communications Protocol (WCCP) on the Cisco Cache Engine and Cisco Content Services Switch (CSS) 11000 or CSS 11500 load balancer.

Before You Begin


For more information on document conventions, see the Cisco Technical Tips Conventions.


There are no specific prerequisites for this document.

Components Used

The information in this document is based on the software and hardware versions below.

  • Cache Engine (CE) 500 running Application and Content Networking Software (ACNS) 4.2 or later

  • CSS 11000 or CSS 11500

The information presented in this document was created from devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If you are working in a live network, ensure that you understand the potential impact of any command before using it.

Background Theory

Transparent caching means that the traffic from a client to a server is silently redirected by a router or a Layer 4 switch to a cache device (Cisco Cache Engine in this case).

If the cache device already has a copy of the content the client is looking for, the cache will reply on behalf of the server. If the content is not present on the cache, the device will try to get it from the server before answering the client request.

By default, the cache will contact the server using its own IP address. It is sometimes necessary, however, to use the client IP address. This is feasible by configuring IP spoofing.


In this section, you are presented with the information to configure the features described in this document.

Network Diagram

This document uses the network setup shown in the diagram below.



This document uses the configurations shown below.

  • CSS 11000

  • Cache Engine 500

CSS 11000
!Generated on 04/18/2003 09:30:41
!Active version: ap10500007s


!*************************** GLOBAL ***************************
  no restrict web-mgmt 
  no restrict xml 
  bridge spanning-tree disabled 
  persistence reset remap 
  acl enable 

!--- An Access Control List (ACL) is needed. Enable the ACL.

  ip route 1 
  ip route 1 
  ip route 1 
  ip route 1

!--- Very important !!!!
!--- For the ECMP feature of the CSS to work, 
!--- you need one route pointing to the upstream router, 
!--- and one identical route pointing to the cache.
!--- The CSS will know which one to use based on where 
!--- the traffic came in first.

!************************* INTERFACE *************************
interface e1
  phy 100Mbits-FD 

interface e2
  bridge vlan 149 
  phy 100Mbits-FD 

interface e3
  bridge vlan 161 
  phy 100Mbits-FD 

!************************** CIRCUIT **************************
circuit VLAN1

  ip address 

circuit VLAN149

  ip address 

circuit VLAN161

  ip address 

!************************** SERVICE **************************
service agra 

!--- Definition of the cache device.

  ip address 
  type transparent-cache

!--- It is important to set the type to transparent-cache
!--- so that the CSS does not NAT the destination IP address.
!--- Only the destination MAC address is modified.

  port 80 
!**************************** EQL ****************************
eql CacheMe 

!--- Definition of what objects are cacheable.

  extension gif 
  extension html 
  extension pdf 
  extension zip 
  extension gz 

!*************************** OWNER ***************************
owner gilles 
  content ToCache 

!--- Definition of the content rule to redirect the traffic.
!--- No VIP address specified since you want to intercept all HTTP traffic.

    protocol tcp 
    port 80 
    url "/*" eql CacheMe 

!--- Redirect all requests of a cahceable object.
    add service agra 
!**************************** ACL ****************************
acl 1 
  clause 10 bypass tcp any destination eq 80

!--- This ACL is necessary to make sure that the HTTP requests from
!--- the cache itself are not intercepted by the content rule.

  clause 20 permit any any destination any 
  apply circuit-(VLAN161) 
acl 2 

!--- Permit all traffic for the other interfaces.

  clause 20 permit any any destination any 
  apply circuit-(VLAN149) 
  apply circuit-(VLAN1) 

Cache Engine 500
hostname CE500
http l4-switch enable

!--- Tells the Cache Engine to accept traffic with any IP destination.

http l4-switch spoof-client-ip enable 

!--- This is a new command in ACNS 5.x. this command replaces the 
!--- wccp spoof-client-ip enable command.

exec-timeout 0
interface FastEthernet 0/0
 ip address
interface FastEthernet 0/1
ip default-gateway
primary-interface FastEthernet 0/0
logging console enable
wccp version 2
wccp spoof-client-ip enable

!--- This commands enable IP spoofing, and it works 
!--- even if you do not use WCCP. This command only works with
!--- WCCP redirected traffic if you have ACNS 5.x.
!--- Therefore, if you are using version 5.x of ACNS, this command
!--- should be replaced with the command http l4-switch spoof-client-ip enable
!--- mentioned above.



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.

CSS 11000 show Commands

  • show summary — Shows the content rule hit counters to see if CSS is receiving and redirecting traffic.

  • show service name — Shows the status of the service.

Cache Engine Commands

  • show stat http request name — Shows the number of HTTP request received by the cache.

  • show stat http savings name — Shows the number of hits and miss on the Cache Engine.


To troubleshoot this problem, use the commands above. Most of the time, however, it is necessary to use a sniffer in order to find out the exact path followed by the traffic.

You can also issue the CSS flow trace command available in debug mode. You will get better result with a sniffer however.

Related Information

Updated: Sep 01, 2004
Document ID: 42162