Transitioning to another ISP

[philblack]

I currently have 2 ISPs. My router is configured with BGP. One of the ISPs will be going away soon and we need to transition our internal DNS and hosted sites from one ISP assigned class c block to the secondary ISP and their respective class c block.

I only have ONE ethernet interface on the router with the OLD ISPs address. All of our hosted sites are on the OLD ISPs class c block. Is it possible for me to assign the secondary ISPs address to the one ethernet interface as a secondary ip address, install and configure a second internal DNS server then slowly reassign IP addresses to the hosted sites? Will I need a second ethernet interface and hub/switch to service this new network?

[mbjohnson]

Yes you can have multiple IP addresses on the Ethernet interface.

Here's an example:

interface ethernet 0/0

ip address 131.108.1.27 255.255.255.0

ip address 192.31.7.17 255.255.255.0 secondary

ip address 192.31.8.17 255.255.255.0 secondary

Hope it helps!