Two identical routers with same config but second one doesn't work

[CPL-RL5]

I have two 8200 routers. One running 12.4(Router A) and a newer one running 12.11(Router B). Router A is on loan while we waited for router B to arrive. I got router A running without issues. When router B arrived, I configured it exactly the same as router A and swapped routers. However, router B will not pass any traffic from interface 0/0/0 or interface 0/0/2 out interface 0/0/1. Devices behind 0/0/0 and 0/0/2 have no problems reaching devices behind one another but 0/0/1 just won't pass any traffic outside from the other two interfaces. I do have ip route 0.0.0.0 0.0.0.0 GigabitEthernet0/0/1 {IP of next hop provided by ISP} on both routers. Router A works as expected but router B doesn't. From the console session of router B, I can ping the next hop IP from ISP and 8.8.8.8 and all routes show up when I do a show ip route. On router A, I can ping interface 0/0/1 and outside from behind interface 0/0/0 but router B just comes back with timed out errors. I've removed all access lists to test and still no improvement. I've made two with just permit ip any any for IN and OUT but still won't work. Hope someone can provide suggestions. Thank you.

[MHM Cisco World]

Ip routing is already work

Run

Debug ip packet <<- share result here 

MHM

[ammahend]

manually clear arp on devices behind B and try again. 

Get show run from A and B, use notepad++ compare tool and compare config, don't rely on visual check. 

[Jens Albrecht]

Hello @CPL-RL5,

if I understand your post correctly, the interface gi0/0/1 is up and running, meaning its status is shown as up/up.

There is a chance that the ISP filters based on the MAC address of the connected routers.

So check the MAC address of router A and configure the MAC address on the interface of router B accordingly.

HTH!

[paul driver]

Hello
As a quick test, spoof the arp from "OLD" rtr  interface and apply it on the new rtr interface see if that helps.

[CPL-RL5]

Thank you, I appreciate all the suggestions. I won't be able to test until the weekend.

[Joshqun Ismayilov]

@CPL-RL5  can you please check NAT -  

#show ip nat translations
#show ip nat statistics

Thanks !