Routing design in core

[The_guroo_2]

Hi Guys i have strange requirement  we have two DNS servers at our main site , Site A (we have two  datacentres) they are virtually one datacenter as far as LAN is  concerened as fibre is connected between the two core switches (at each  datacentre) and EIGRP is running between them. Both DNS servers are at  main site( site A)

The subnet ID is 192.168.1.0/24 and DNS servers IP's are 192.168.1.7 and 192.168.1.8.

Now  the requirement is that we are building site C as we have to vacate  site A and requirement is that we shift all DNS servers to site B (keep  in mind that 192 subnet only resides at site A and is reachable via  EIGRP from site B). The issue is that we have to retain the same subnet  as we have no visibility how many host uses it so it has to be same  subnet to make things worse DNS team has said that they ave to move one  server at the time.

Can someone advise how it can be done as i am lost.

Thanks as usual

[Neeraj Arora]

I can think of only one way out (other might have a better solution)

Fiber connectivity between two Cores, make it Layer 2 i.e extend the 192.168.1.0/24 vlan to your Site B. I am hoping that its not Vlan 1 on both sites

[blau grana]

Hello,

Probably there will be some more elegant solution, but this could also work.

At site B you can create Loopbacks with 192.168.1.7 and .8 addresses with mask /32 which will be prefered before /24 network. You start advertise this loopback after DNS server will be migrated.

Migrated DNS servers will be temporaty on other subnet and will be NATed 1:1 to Loopbacks. After migrating both DNS, subnet 192.168.1.0/24 will be also migrated to site B and DNS servers will be migrated to this subnet.

This can not be done without outage, but it can be done with only one DNS server outage simultaneously.

Best Regards

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