BGP Best Practise for Internet Providerchange

[MANFRED LIEBCHEN]

Best Practise for Internet Providerchange

Our Network is in i.e. AS 5000; we have a Singe Home Environment with multiple links connected to one ISP(Carrier1) which is in i.e. AS 8000 terminating on two different Routers (border1-gw and border2-gw) located in our Network connected together via IBGP.

                        Carrier 1     RTR-A                          RTR-B
                        AS 8000       |     \                           /    |
                                            |       \                       /      |
                                            |         \                   /        |
            Our Network       border1-gw ------- border2-gw
                  AS 5000

border1-gw and border2-gw are both Cisco ASR9904 running with IOS XR 6.6.3

At the moment we receive a defaultroute and complete Routingtable from Carrier 1; our ingress/egress traffic is asymmetric which means, both Routers are active/active.
We announce 7 Prefixes to Carrier1

Example Addresses are arbitrarily conceived
address-family ipv4 unicast
140.70.0.0/16
185.200.100.0/22
130.80.216.0/23
130.80.209.0/24
130.80.225.0/24
130.80.226.0/23
address-family ipv6 unicast
2c00:a300::/32

We want change our Internetprovider from Carrier1 to Carrier2 !

during migration we will have a Multi Home Environment with multiple links connected to two different ISP(Carrier1 and Carrier2) which are in different AS(8000 and 6000) terminating on two different Routers (border1-gw and border2-gw) located in our Network connected together via IBGP.

                        Carrier 1     RTR-A                          RTR-B
                        AS 8000       |     \                           /    |
                                            |       \                       /      |
                                            |         \                   /        |
            Our Network       border1-gw ------- border2-gw
                  AS 5000             |    \                          /     | 
                                            |       \                      /      |
                                            |         \                  /        |                             
                        Carrier 2     RTR-1                    RTR-2
                        AS 6000

We will receive default route and full routing table from Carrier1 and Carrier2;

we DO NOT become a transit path for either ISP !Please add an example configuration for this purpose if possible.

After Migration we have a Singe Home Environment
with Carrier2 only quite the same connection see at the beginning of my question.

What is the best way -minimal interrupt- to move Prefixes from Carrier1 to Carrier2 ? Carrier1 shoul be backup for ingress/egress, Carrier2 should become active for ingress/egress;

i think moving each prefix seperate would be the best way with minimal impacts.

Any hints and IOS XR configuration examples are welcome

Thanks in advance Manfred

[MHM Cisco World · Accepted solution]

https://networkdirection.net/articles/routingandswitching/bgppreventtransitas/

prevent transit AS.

[MANFRED LIEBCHEN]

thanks very much; your hint was exactly what i was searching for

Greetings Manfred

[Flavio Miranda]

This could be an easy task except for one point ("We will receive default route and full routing table from Carrier1 and Carrier2")

Why is that? If  we are talking about single home, why dont you accept only the default route? Then, you can do it in "big bang" mode, I mean, On day X, you stop accepting default route from Carrier1  and start acception from Carrier2. Totally under your control.

[MANFRED LIEBCHEN]

Hi

we have some other peerings witch special route policies i did not mention in my question

Regards Manfred

[Georg Pauwen]

Hello,

can you elaborate on that ? Does that mean you will still be connected tp ISP1 somehow ?