Problem NAT inside

Question:

a have a router CISCO 1841 WS-C3560V2-24TS-S and I configured a NAT inside from the router to the firewall like this :

ip nat inside source static firewall_adresse  public_adresse and its work fine and when a added it I do this command "wr" to save the configuration and I restarted the router many times and it still work fine

but in the last five months this NAT does not exsit twice and I must add it a gain

can you help please or explain why happened this

Answer:

This look like a software issue. Check if your IOS is hitting the following software defect -

CSCsi30964  

Static NAT statement disappears from running-configuration

tools.cisco.com/Support/BugToolKit/search/getBugDetails.do?method=fetchBugDetails&bugId=CSCsi30964

Also please post the output of show run, sh ver and which NAT statement observed issue.

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Here are the bug details -

+++++++++++++++++++++++++++

Symptoms:

On a Cisco router performing NAT, static NAT statements may disappear from the running-configuration during operation. Any new flows requiring translation via the missing statement may fail.

Conditions:

- This problem was first experienced in IOS 12.4(9)T.

- It has only been reported for extendable, inside source static NAT statements

for TCP ports 80 (HTTP) and 25 (SMTP), with and without a route-map:

Examples:

ip nat inside source static tcp x.x.x.x 25 y.y.y.y 25 extendable

ip nat inside source static tcp x.x.x.x 25 y.y.y.y 25 extendable route-map nonat

ip nat inside source static tcp x.x.x.x 80 y.y.y.y 80 route-map nonat extendable

- After the statement disappears from the running-configuration, it is still

visible in the startup-configuration.

- Existing translations created before the disappearance are cached in the NAT

translation table and continue to work correctly.

Workaround:

Reload the router.

+++++++++++++++++++++++++++

Could you confirm following : Was the NAT translation there in startup-config, once it was not seen in running-config ?

You are using 124-11.XJ4 IOS. I don't think the defect is resolved in this IOS.

In mainline train the defect is fixed from 12.4(18b) onwards.

Please check the Release notes and features in use available in the mainline release if you are planning for upgrade.

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Cisco 1841 (revision 7.0) with 115712K/15360K bytes of memory.

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You have 128 Mb of DRAM on this router.

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I'm not sure if I understand your question correctly..

Are you telling when the VPN traffic is going via this Router, then when you type show run it doesn't show you the output.

and when the VPN traffic is blocked, you are able to see the output.

If that is the case, you may need to check CPU & Memory Utilization, Interface counters on the Router when the issue is happeneing to determine the exact cause.

sh proc cpu sorted | ex 0.00

sh mem stat WS-C3560V2-48TS-S

sh interface