# Cisco IP address conflicts



## evo22 (Jul 18, 2006)

Hello,

I just configured a new Cisco 1841 Router and attempted to replace our existing router last night and it cause network IP address conflicts with our servers? Sounds like a NAT problem...does anyone know how to fix this issue?

Thanks in advance


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## Ericunicast (Aug 23, 2006)

how was the router configured? staticly or by using a routing protocol, RIP, IGRP etc.?


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## evo22 (Jul 18, 2006)

The router has a static IP and the servers have static IPs. I solved the problem with the conflict. Now I'm having problems with the Firewall, it's only allowing out bound traffic...we host our own website and it will not in coming traffic to our website? I tried IP forwarding no luck.... Any suggestions short of contacting Cisco support?

Thanks in advance...


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## Ericunicast (Aug 23, 2006)

What type of firewall are you using and at what point in the network are you NATing? sounds like another NAT issue.


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## evo22 (Jul 18, 2006)

The Firewall we are using is the built in Cisco 1800 series firewall.


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## Ericunicast (Aug 23, 2006)

The only possible problems i can think of are potential NAT problems. Im stumped for now. Its not an overload because that would eliminate traffic all together. Ill get back to you in a few.


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## evo22 (Jul 18, 2006)

Thanks I appreciate it!


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## terbolee (Sep 4, 2006)

Can I assume you've checked the ACLs to make sure they are working right? On the router, check the existing routing table [show ip route] to make sure that all known routes should be there. An IP address conflict can confuse a router causing it to build an incorrect routing table. You might try clearing the routing table so it can build a new one. I think the command is [clear ip route *] in the Global Configuration mode. Hope this helps.


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