Spontaneous static NAT entry being created in IOS 12.3(12)

Hello,

I have an IOS router (2651) configured to do NAT. I have a dynamic NAT pool for my internal 172.16.0.0/16 network and also have static NAT entries for three IP addresses in that network. (172.16.0.18,

I called Cisco when I noticed that the router appeared to have spontaneously created a static NAT entry for 172.16.0.16 that mapped to one of the IP addresses in my dynamic NAT pool. This was a problem because I have an access list on the dynamic NAT pool that prevents NAT under certain circumstances, and a route map that prevents NAT on the static entries. Since the static entry for 172.16.0.16 was spontaneously created, traffic was not being passed properly to the destinations that required NAT to be disabled.

I was curious if anyone else has seen similar behavior and knows what might have caused this. I have upgraded to 12.3(15) (from 12.3(12)) and haven't seen the problem again, however it took at least two weeks to show up before.

To give you an idea of the spuriousness of this, here's a snippet of a CLI session on my router that should be impossible:

router#conf t Enter configuration commands, one per line. End with CNTL/Z. router(config)#no ip nat inside source static 172.16.0.16 99.88.77.66

Static entry in use, do you want to delete child entries? [no]: y %Translation not found router(config)#exit router#clear ip nat trans * router#conf t Enter configuration commands, one per line. End with CNTL/Z. router(config)#no ip nat inside source static 172.16.0.16 99.88.77.66 %Translation not found router(config)#exit router#

These two lines are the clearest indication of a defect in the IOS:

Static entry in use, do you want to delete child entries? [no]: y %Translation not found

How can the static entry be in use if it doesn't exist?

Thanks in advance for your help.