Migrate the Public IP subnets from ISP to our DC

[Ivan Adji - Krstev]

Hi all, 

I would like to migrate all the public IPs ( this are ours IPs ) to our Newly Router. Or in short take control of the AS number and put it in new DC.

Currently we have DC and Router that is ISP control. Now we migrate to different DC and we want to manage the AS ( Public IPs ) our self. So we have x.x.x.x in DC1 and we want to migrate x.x.x.x in NewDC. As i know this should be done via BGP but i would need some steps and how things will work if we have to same IP address active. I know that may Geolocation is coming in game but still I want some advice and hints on how to do it. 

Kind regards

Ivan

[Philip D'Ath]

I see several options.

1. Do a cold cut over.  Stop advertising from the old DC, and start advertising from the new DC.  There will be an outage.

2. Build a GRE tunnel from the old DC to the new DC, and run iBGP over that.  That if traffic turns up at the DC you don't want you can re-route it to the correct DC.

2. Build a layer 2 circuit between the sites.  This can be done with a service provider QinQ circuit, or you could use a pair of routers and build a L2TPv3 circuit between them.  The advantage of this is that VLANs will be extended across both sites, so you can have the IP addresses active at both sites at the same time, and you can move machines across "one by one".

[Ivan Adji - Krstev]

So with option 2 looks like Live migration where on both Sites i have the same IPs ?

As i imagine that scenario where i will have all subnets ( public ones ) propagate on both ends ( Old DC and New DC ) and till we migrate all Apps than we can cut it out the Old one. 

If so, what will be the scenario for it?

[Philip D'Ath]

You just build a GRE tunnel between the two outside interfaces, run iBGP over it.

You then have to migrate all the machines in the subnet as you move it from the old DC to the new DC in one go.

[Ivan Adji - Krstev]

And is there a way to transfer /26 subnet. For example we have one subnet x.x.x.x/26 and we need this one to be migrate in the new DC with new ISP. I can't find a solution for this. One of the ISP says that this can't be done. And im saying that must be a way. :)

[Philip D'Ath]

You have to migrate a minimum of a /24 at a time.

So advertise that /24 to both ISPs, and build a GRE tunnel between your routers, to route the appropriate subnet(s) back to the correct DC.

[Ivan Adji - Krstev]

So there is no way to keep the /26 subnet ? :( This is subnet is specific for us, i was hoping to keep this and all others we can go with new but ... it get opposite :) 

[Ivan Adji - Krstev]

And what about advertise the routes to/with that subnet ?

[Philip D'Ath]

First build a GRE tunnel between the outside interfaces of the routers, and get BGP running over that.  You need to get both sites aware of which routes are at which sites.