Cisco 800 ADSL for some reason broadcasting on 2 internal IP's

[edeyzel-bba]

Hi,

I have a verys strange issue. All of a sudden one of our PC's with a static IP got a IP conflict. Upon further investigation it came to light that the IP and traffic is originating from out Cisco 800 ADSL router.

Now, the setup is like this - Router main IP is xxx.xxx.xxx.1, the conflicting IP is xxx.xxx.xxx.11.

Both IP's come back with the same MAC address and when we unplug the Cisco router from the network .11 is no longer reachable.

The Cisco is only connected to the DSL modem and Interface 3 on the router that is connected to the main switch and that is it.

Now, this router is in France and I am in the UK so I do not hve physicle access to the router but according to my guy on the ground thats the setup.

I checked all over the configuration of the device but I cannot see that IP configured anywhere.

Some help wpuld be appreciated.

[ANDREY KRASHENINNIKOV]

There are many reasons for the appearance of the second address. Please show complete running congiguration or output

sh run | in xxx.xxx.xxx

xxx.xxx.xxx is part of main IP address.

[edeyzel-bba]

Hi,

ip dhcp excluded-address 192.168.77.1 192.168.77.19
   default-router 192.168.77.1
 ip address 192.168.77.1 255.255.255.0
ip nat inside source static tcp 192.168.77.11 48840 80.13.228.185 48840 extendable
ip nat outside source static tcp 80.13.228.185 48841 192.168.77.11 48841 extendable
ip nat outside source static tcp 192.168.77.11 48840 80.13.228.185 48840 extendable
logging 192.168.77.10
access-list 100 permit tcp any host 192.168.77.1 eq 48841
access-list 100 permit tcp any host 192.168.77.1 eq 48840
access-list 105 deny   tcp any host 192.168.77.1 eq 48840
access-list 105 deny   tcp any host 192.168.77.1 eq 48841

I see some NAT rules in there but how do I get rd of them?

Sorry, a bit new to Cisco.

Thnaks fpr the reply btw.

[ANDREY KRASHENINNIKOV · Accepted solution]

Yes you are right it is NAT.

The router change ip address from 80.13.228.185 to 192.168.77.11, therefore got a IP conflict

[edeyzel-bba]

Thanks, issue resolved, thanks for putting me on the right trail.