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Step-by-Step Configuration and Troubleshooting Best Practices for the NGFW, NGIPS and AMP Technologies A Visual Guide to the Cisco Firepower Threat Defense (FTD)
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IP Conflict on PIX Outside Interface

Please excuse my ignorance but I have a problem with a PIX 525 (failover) that I just cannot figure out.

The outside interface has an address with a /27 mask. I am using a few statics to NAT inbound connections(for FTP use, etc). And the global I am using is the outside interface.

I have recently been asked to put a further FTP server inbetween the outside of the PIX and default gateway and assign it a public IP within the /27 range. When I do, Windows (FTP server) complains of an IP address conflict and never assigns the NIC an address.

Any ideas? - as you can probably guess I am not an expert.


Re: IP Conflict on PIX Outside Interface

Do a ping swwep of the public network and find an IP that is not being used. However you'll also want to check your firewall and see what is being used (your static NAT's). Also from your internet router, take a look at your ARP table, it should see what public IP's have been learned (ie used).

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Re: IP Conflict on PIX Outside Interface

Thanks for the prompt reply. The statics are Ok and I used a relatively high number in the addressing using the assumption nothing would be using it.

I also tried to place it within a dmz and perform a no nat operation - this didn't work either. See my next post.

I put this PIX in about five years ago and the only thing I have done since is the occassional static and access-list. It just works. It is very frustrating when no option seems to work.

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