Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 
Community Member

NAT with Secondary IP on 2620

I have a 2620 that has a T1 on serial 0 and then a Public network IP 63.X.X.X on Fa0/0 with a /27 subnet. My question is I want to set up a secondary IP on fa0/0 ie: 10.10.20.X. I want to use NAT for my private network with the translations from the 10.10.20.X network to the public network on fa0/0. Is this set up possible? Sorry but I have a hard time explaining things maybe I can clarify better in an email offline. thanks

Community Member

Re: NAT with Secondary IP on 2620

I am not quire sure what you mean by this, but I hope this may answer your question. When you do NAT on an interface, I have had problems with secondary IP blocks not passing to the interface with NAT. Even if you put the ip address secondary on the interface, you cannot route to it. I have gotten around this problem with using:

interface Serial0

ip address

ip access-group 111 in

no ip directed-broadcast

ip nat outside


interface FastEthernet0

ip address secondary

ip address

ip access-group 1 in

no ip directed-broadcast

ip nat inside



ip nat pool FSE-natpool-1 netmask

ip nat inside source list 1 pool FSE-natpool-1 overload

ip nat inside source static no-alias

ip route

ip route FastEthernet0

Notice the (ip route FastE0). This was done because the block was not routing through the NAT and was getting kicked out.

Let me know if this is not what you are looking for.


CreatePlease to create content