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Network Warrior, 2nd Edition by Gary A. Donahue

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Troubleshooting

If you change an access list, change NAT, or do anything else that can alter which packets are allowed to flow through the firewall, you may not see the results until you execute the clear xlate command.

Xlate is short for translation. A translation is created for every conversation that is active on the ASA. To see which xlates are active on your ASA, use the show xlate command:

ASA-5540# show xlate
4 in use, 4 most used
Global 10.0.0.10 Local 192.168.1.10
Global 10.0.0.11 Local 192.168.1.11
PAT Global 10.0.0.6(80) Local 192.168.1.6(80)
PAT Global 10.0.0.6(443) Local 192.168.1.7(443)

The PAT Global entries are live connections from my PC to the Web. I had a download running through a web browser, plus a few web pages open. The last entry is a static translation resulting from the static configuration entered earlier.

To clear xlates, use the clear xlate command:

ASA-5540#clear xlate

Warning

When you clear xlates, every session on the firewall will be broken and will need to be rebuilt. If your ASA is protecting an ecommerce website, transactions will be broken and customers may become unhappy. You should not clear xlates unless there is a valid reason.

While the clear xlate command runs with no fanfare on the ASA, every connection will be cleared. My IM client reset, and the download I had running aborted as a result of the xlates being cleared.

Another useful command for troubleshooting is show conn, which shows all of the active connections on the ASA:

ASA-5540#sho conn ...

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