NAT Problem?

[oldzy]

Hello,

We have a 2621 router that keeps acting up ever few days, normally in the morning when staff come in. Staff cannot access the Internet at all or any internal servers by either IP or NAME. However, all incoming traffic seems fine. Restarting the router corrects everything until the next occurrence.

We are running NAT, and it seems to be the issue but not 100% certain. Sometimes the 'Inside local' IP Address is actually a Public IP on one of existing servers, and is already assigned a Static IP. Is this normal? It so happens that this particular server/website is inaccessible until a 'clear ip nat trans *' is done (sometimes the website is accessible w/o clearing the dynamic NAT translations though). There was also some AOL Public IP Address assigned to the NAT Pool IP as well as above.

We are using the below IOS release.

12.1(21)

c2600-io3-mz.121-21.bin

Any suggestions?

Thanks,

Ken

[a-vazquez]

When you have IP connectivity problems in a NAT environment, it is often difficult to determine the cause of the problem. Many times NAT is mistakenly blamed, when in reality there is an underlying problem. This document demonstrates how to verify NAT operation using tools available on Cisco routers. This document also shows you how to perform basic NAT troubleshooting, and how to avoid common mistakes when troubleshooting NAT.

http://www.cisco.com/en/US/tech/tk648/tk361/technologies_tech_note09186a0080094c32.shtml