2 ISP In-place Migration

[Jason Young]

We are replacing our Internet carrier and struggling to find the best method to migrate our IPs over with Zero downtime given the DNS replication lag around the world.

We have 4.5 Mb connection from Windstream into a 2901 Router with 3 public ranges assigned to us. We are migrating to a 10Mb AT&T connection into the same router with 1 large public ip range. Behind the router is a pair of Active/Passive ASA 5510's.

We have been kicking around ideas to make the migration with no downtime knowing that the servers behind the firewall really need to answer on both public IPs for a day or two to ensure there is no downtime.

We have thoughts but nothing we are comfortable with yet. I am sure there is something really simple we are not thinking of, so I figured I would ask for some help.

Adding to the mix we are going to replace our firewalls which can be done ahead of time, during or after if that would make it any easer.

Any help would be greatly appreciated.

Thanks,

Jason

[Tarjeet Singh]

Just move your connection to temporary router and then configure your production router and then move internet line back to your production router. There will be short blip if you could flip cable between these two routers quick enough. You can buy linksys router. This router will keep our connection in mean time you can configure your router. 

[Jason Young]

Tarjeet,

I am confused on how this would help me.  For example we host websiteA.com, when we change the DNS for that site it would take 24 hours to replicate and I would need the website temporarily avalible on both IP's until the new DNS has completed replication. 

While I do have extra routers that I can setup I am not sure how it would help in this case.

Thanks,

Jason

[thomas.g.fan]

not sure if this works for you but worth a look:

phase 1

phase 2

phase 3

[Gajendra R']

Hi Jason,

As per Jason post you can register DNS A record for your New & Old as well. Then if you have extra router and Switch  you can connect with firewall. as you said DNS registration will take at least 24 hrs. Hence you can put a backup route with Tracking in ASA towards to your new ISP line. once you done with DNS registration you can go for AT&T line state forward..

:-)