Troubleshooting the Cache Engine

This chapter covers some tasks that might help you resolve problems you might encounter with the Cache Engine. If you cannot resolve your problem using the Cache Engines' management interface, or with the information in this guide, please contact Cisco Technical Support for further help.

Determining Why the Cache Engine Cannot Connect to a Web Server

If the Cache Engine cannot reach a specific web server, try pinging the web server. If the Ping is unsuccessful, try tracing the route to the server. Look for loops in the route (where the packets are sent through the same set of routers continuously, so that the packets do not get outside a certain ring of routers).

If the Ping is unsuccessful, and there is a loop in the route, contact the owner of the looping router and tell them that they have a routing problem.

If the Ping is unsuccessful, but there is no loop in the route, then the web server is having a problem, or may no longer exist. Contact the owner of the web server, or wait until they find and fix the problem themselves.

If the Ping is successful, but you cannot connect to the web server using a web browser, then the web server may not be currently running on the target machine. Contact the owner of the web server, or wait until they find and fix the problem themselves.

You can also simply disable the Web Cache Control Protocol on the router, and see if you can then connect to the web server. If you still cannot make the connection, then the problem is not with the Cache Engines, but with the web server.

Determining Why Data is Not Being Cached

If the Status page for a Cache Engine shows that no data is being cached, you have not specifically turned off caching for the machine by removing it from the cache farm, and you know that the traffic you are testing with uses port 80, follow these steps to determine why the machine is not caching data:

Step 1 Use the show ip wccp EXEC command on the home router for the Cache Engine to determine whether the router is running the Web Cache Control Protocol. This command should also show the number of Cache Engines available to the router. If the router is not running the protocol, start it using the ip wccp command.

Step 2 Use the show ip interface EXEC command on the home router for the Cache Engine to determine whether the outbound interfaces are redirecting web packets to the cache farm. The output should show "Web Cache Redirect is enabled" for each outbound interface. If the interfaces do not have web cache redirection enabled, enable it for each interface using the ip web-cache redirect interface command.

Step 3 Use the show ip wccp web-caches command if the number of Cache Engines displayed in the show ip wccp command is less than expected. Any engines shown with this command should be fully configured and functional. If an engine is not listed, connect to that engine's management interface, click Nerd Knobs, and fix the configuration of the engine. Ensure you are using the correct IP addresses for the engine, its home router, and its gateway.

Step 4 If all configuration parameters appear to be correct, and the home router is running the required protocols, try rebooting the Cache Engine. Click the Nerd Knobs button, and click Reboot in the Heart Monitor group, then click Do It in the Heart Monitor group.

Step 5 If the Cache Engine is still not caching pages, contact Cisco Technical Support for assistance.

Determining Why Customized Pages Are Not Correct

Many web pages use cookies to customize the page for the user. If users complain that they are not getting correctly customized pages, this may indicate that the web server is not set up correctly to include the appropriate caching parameters in the HTTP header. You can try to convince the owner of the web server to address this issue, or you can turn off cookie caching in the cache farm. If you turn off cookie caching, only the HTML page that uses cookies is not cached; graphics and other objects on the page are cached according to your MIME blocking settings.

To turn off cookie caching:

Step 1 Click Nerd Knobs. The Freshness Factor group controls cookie caching.

Step 2 Check Off for Cookie Caching.

Step 3 Click Adjust in the Freshness Factor group. The Cache Engine sends a message to all the engines in the cache farm, so that every engine uses the same freshness factors.

Obtaining Information for Technical Support

Use the TechSupport command to gather information that can help Cisco Technical Support personnel diagnose and resolve problems you might be having with your Cache Engine. The syntax of the TechSupport command is:

TechSupport

Command Environment

You can use the TechSupport command from the Cache Engine console or from a Telnet session. You cannot use the command when running from the recovery diskette.

Example

In this example, not all of the output of the command is shown; only the major sections of command output are displayed.

->TechSupport

Version: CE v1.2.5 (12-23-97) [/ata0/1_2_5.dir]

Software Configuration for Cache Engine

Config Version = 1

Time = 18:58:51, Date = 01/06/1998

Network

(****Network information****)

DNS

(****DNS information****)

Proxy

(****Cache Proxy information****)

Local CFC Latency

(****Cache CFC information****)

Freshness Factor

(****Freshness Factor information****)

Filters

(****URL Filtering information****)

Syslog host is valid.

(****SYSLOG information****)

MulticastDump 

(****MulticastDump output****)

  CPU Utilization: OneSec: 1  TenSec 1

  NET Utilization: OneSec: 0  TenSec 0

  DISK Utilization: OneSec: 0  TenSec 0

memShow follows:

(****memShow output****)

ipstatShow follows:

(****ipstatShow output****)

tcpstatShow follows:

(****tcpstatShow output****)

inetstatShow follows:

(****inetstatShow output****)

routeShow follows

(****routeShow output****)

routestatShow

(****routestatShow output****)

General Stats

(****Disk usage information****)

Table 5-1 describes the fields in the TechSupport command output.

Table 5-1: TechSupport Command Output

Field	Description
Version	Displays the directory that contains the active software version, and the version information.
Software Configuration for Cache Engine Config Version Time Network DNS Proxy Local CFC Latency Freshness Factor Filters Syslog host	Displays the configuration information for the Cache Engine. Most of this information is set through the Cache Engine's management interface, and can also be viewed through that interface.
MulticastDump	Displays the status of the cache farm.
CPU Utilization	Displays the average CPU usage over the previous one- and ten-second intervals.
NET Utilization	Displays average network usage over the previous one- and ten-second intervals.
DISK Utilization	Displays average disk usage over the previous one- and ten-second intervals.
memShow follows:	Displays available and allocated memory.
ipstatShow follows:	Displays overall statistics for IP errors.
tcpstatShow follows:	Displays overall statistics for TCP transactions.
inetstatShow follows:	Displays current active Internet connections.
routeShow follows	Displays assigned gateways and route host tables.
routestatShow	Displays overall statistics for routing errors.
General Stats	Displays overall statistics for disk usage.