Hi all,

Currently, we're an AS with a /24 prefix. We're advertising these IPs through 2 peers.
The problem is that we'll need to move our datacenter, physically, to the new company address.

What is the best solution to this case? We bought another CCR just in case we need to keep it powered on in the new location.
Is there a way we can advertise the same /24 on this router too, simultaneously? Or is it best to establish BGP session but not advertise the prefixes yet?

Is there a way we can advertise the same /24 on this router too, simultaneously? Or is it best to establish BGP session but not advertise the prefixes yet?

You could only advertise the same /24 if the two locations are connected by some other means (ex. layer 2 circuit between them), or at least some kind of tunnel over IPs that are not part of that /24. Otherwise you could have packets returned to datacenter B that are meant for datacenter A and the other way around, without a way of getting the packets to the correct place.

You could only advertise the same /24 if the two locations are connected by some other means (ex. layer 2 circuit between them), or at least some kind of tunnel over IPs that are not part of that /24. Otherwise you could have packets returned to datacenter B that are meant for datacenter A and the other way around, without a way of getting the packets to the correct place.

Thanks @mducharme.
So, if we got a L2 communication between the two sites, how the BGP configuration will look like? I mean, we currently have two peers on site A, how can I advertise the same /24 network to the same peers (ISPs) on site B? There is a need for iBGP here? Or are you referring to only establish a BGP session on site A and transport the routes stacticaly to site B?

Or, even is it a better approach to establish a BGP session on both sites, but with peer 1 on site A and peer 2 on site B only?

I would do this by simply advertising the /24 at both physical locations. And then have your own connection between these 2 locations and run iBGP or OSPF between the routers (you can use EoIP or any other tunnel for this in the meantime)

so i.e. you have 1.2.3.0/24 advertising out both locations, but .0-.192 are physically still at LocationA and .193-.255 are physically at LocationB
Start with just regular BGP at both locations, you aren't able to control where traffic comes in, sometimes traffic destined for .167 hits LocationB but its ok because B knows that it lives on A via OSPF/iBGP and just sends the traffic over the tunnel. And the opposite occurs for traffic destined to i.e. .223

Once its all working and you are happy, you can AS-prepend at A to lower the priority of incoming traffic (you could also make B the preferred default route from A, so ALL outgoing traffic goes to B first)
Then once most traffic is moved just stop advertising BGP at A entirely, wait till traffic dies off completely and then remove the router

If you are using full tables, OSPF can't handle those, so you will want to iBGP peer those two routers to make sure that they have the same view of the global routing table. If you are only getting a default route, that probably isn't necessary.

If you are using full tables, OSPF can't handle those, so you will want to iBGP peer those two routers to make sure that they have the same view of the global routing table. If you are only getting a default route, that probably isn't necessary.

I wouldn't be advertising the BGP table across the link, no no, just advertise the specific /32 addresses of the /24 block (and any other infrastructure/private IP's) between the 2 edge routers so traffic gets to where it has to
the eBGP routes stay on each router they don't advertise those to each other