ASR reporting duplicate ip address

[dan.letkeman]

Hello,

I have an odd problem with an ASR1001 and a 3560G.  The ASR is for some reason reporting that there is a duplicate ip address on the link between the 3560G and the ASR

ASR#show ip arp

Protocol  Address          Age (min)  Hardware Addr   Type   Interface

Internet  10.110.1.1              -   4c00.8203.a781  ARPA   GigabitEthernet0/0/1

Internet  10.110.1.2              -   4c00.8203.a781  ARPA   GigabitEthernet0/0/1

interface GigabitEthernet0/0/1

description Inside Interface

ip address 10.110.1.1 255.255.255.252

no ip redirects

ip nat inside

negotiation auto

cdp enable

ip virtual-reassembly

3560G#show ip arp

Protocol  Address          Age (min)  Hardware Addr   Type   Interface

Internet  10.110.1.1              -   4c00.8203.a781  ARPA   GigabitEthernet0/2

Internet  10.110.1.2              -   00c5.4592.bcd4  ARPA   GigabitEthernet0/2

interface GigabitEthernet0/2

no switchport

ip address 10.110.1.2 255.255.255.252

Doesn't matter what we do it always thinks the mac address of the adjacent device is actually itself.....very frusturating.

Any ideas?

Thanks,

Dan.

[Lei Tian]

Hi Dan,

Was that interface IP misconfigured before? Did you try reload the router? Does it break traffic forwarding between ASR and 3560? Can you config static ARP for the IP?

HTH,
Lei Tian

Sent from Cisco Technical Support iPhone App

[dan.letkeman]

This is a lab setup.  Yes it breaks ip forwarding between the router and switch.  Static arp does not help.

It's very odd, but I think it might having something to do with nat.  If I configure the 3560G with a different ip (10.110.1.3) then it all works, until i configure a static outside nat entry, then the router takes and add's 10.110.1.3 as a duplicate ip address as well!

[Lei Tian]

Hi,

Are you using neighbor IP in your NAT config? If that's case, then is expected.

HTH,
Lei Tian

Sent from Cisco Technical Support iPhone App

[dan.letkeman]

No we are not using the neighbor command.

[paul driver · Accepted solution]

Hello

Try using the no-alias command on you statics nat entrys

res

Paul

Please don't forget to rate any posts that have been helpful.

Thanks.

[dan.letkeman]

I will try this when it happens again, but it actually stopped the duplicate ip messages....for now.