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STATIC NAT Problem on IOS 15.x

Few are the issues that I am facing on IOS Version 15 and Cisco 1941 Router , this router is currently in production on clients.

  • •1.        I do PAT on router interface , and it has public IP on it , when I send  request to Internet via Browser from LAN client , Page does not open  and when I check  NAT TRANSLATION on router , Router does translate the  packets. The work around I found is that when I disabled CEF on router ,  Web starts browsing ,  Why does this happen and why I need to disable  CEF ?

  • •2.        I have Public IP Pool its subnet mask is /29 , one of the Public IP  from this pool is live on the interface. When I perform STATIC NAT a web  server resides in LAN , then I can access this server from anywhere in  the world by IP.

After  few days Static NAT stopped working , I again Static NAT it on other  Public IP , the same issue rise again , I am not able to access this  server from Internet. This issue has been faced at two clients.   The  same pool i have checked on 1841 router and static nat works fine on the  same public IP .  

I have upgraded the IOS as well to version 15.1 but  STATIC NAT issue is not solved.

Please Help me out in this regard.

I would be grateful

Everyone's tags (4)
Cisco Employee

STATIC NAT Problem on IOS 15.x


This forum is to discuss specific bugs and the bug toolkit/bug sarch tool.  This question is probably better asked in "Wan, Routing and Switching" or with a TAC case.

To increase the chance of getting an answer, you should provide the exact version of software and relevant configuration snippets.

A quick check on the Bug Search tool on "cef nat" may help.  I see a few candidate bugs when I do that.

Bug search tool: