IOS NAT translation (destination??)

[grnelson]

We are moving to a  new data center and re-addressing all central hosts.

Our DHCP server is  currently at address 192.168.16.200 so naturally, we have

a helper-address of  192.168.16.200 configured on L3 client interfaces.

If possible, we  would like to avoid changing the existing helper-address on every L3  interface.

Let's say the DHCP  server's new address is 10.1.1.1.

I would like to use  NAT translation so that an incoming  DHCP packet with destination 192.168.16.200  gets translated to 10.1.1.1.

We would announce a  route for 192.168.16.200/32  on the router having the L3 interface to the DHCP  server  pointing at a next-hop loopback interface. When a DHCP packet passes  through the loopback interface the destination address is translated to 10.1.1.1  and the packet is sent to the DHCP server's new address. The DHCP server replies  to the source address.

This would let us  configure an enterprise-wide helper-address that would never have to change. We  would just change the NAT translation in the router to which the DHCP server is  connected.

Can this be done in IOS? Is there a better way to do this?

[Jon Marshall]

We did something similar when we migrated to a new DC although in our case it was only temporary until we updated the ip helper-address so it will work.

something like -

ip nat inside source static 10.1.1.1 192.168.16.200

on the DHCP server connected router. The inside interface would be the one connected to the 10.1.1.1 network.

FYI, we used a perl script to actually update the routers, relatively straightforward ie. it logged into the router using perl expect and then replaced the existing ip helper-address with the new one. Sorry i can't provide the script as i have since left the company and didn't make a copy but i remember it was fairly trivial to write.

Jon