BGP Design Migration

[Steev112]

Dear All

I have internet router (IR-1) connected to Core switch and three ISPs this router is very old, my plan is bring new internet router (IR-2) and do following steps for shifting the traffic :

1.       Enable IBGP between IR-1 and IR-2.

2.       Shift ISP-1 to new router IR-2

3.       Shift ISP-2 to new router IR-2.

4.       Shift ISP-3 to new router IR-2.

5.       Shift the Core switch to new router IR-2.

6.       Remove the old Internet Router (IR-1) from the picture.

Can you please tell me what the best practice to do this migration?

Are the above steps enough or there is steps I have to take in my consideration?

I really appreciate your concerns.

Best Regards,

[Akash Agrawal]

Hi Stevan,

For seamless transition I would suggest below steps

1. Connect a 10G link from core switch to IR-2 and enable all protocol on link (IGP,MPLS,PIM) as it is there on IR-1 and BGP with RR.

2. When IR-2 is having full connectivity with core network as IR-1, then move one link of ISP-1 to IR-2, establish eBGP peering with ISP-1 over loopback ip.

3. Set lower LP on IR-1 for ISP-1 prefixes to move forward traffic via IR-2.

4. Advertise prefixes to ISP-1 on R1 with AS-PATH prepend to move reverse traffic via IR-2.

5. Once forward and reverse traffic for ISP-1 is moved to IR-2, you can shift another link also to IR-2.

6. Repeat same steps to move ISP-2 and ISP-3 links.

7. Now traffic on link between core switch and IR-1 should be zero. If it is, you can remove the old Internet Router (IR-1) from the picture.

Regards,

Akash

[Sandeep Sharma]

Hi Steven

Your plan seems fine but I will prefer to remove the old router from the path asap. So in place to shifting the core switch to new router on 6th step we should prefer to do it on first step or second and later passively without any impact you can shift the left ISP link one by one or in one go.

Thanks & Regards

Sandeep

[ravikantt]

  Hi Steven,

Well, what I'm suggesting could be configurational task, but why don't you run VRRP after connecting new device, & make new device Master, later on , if you want,  can remove the the VRRP config as well.

Cheers

Ashok