Multiple ISP BGP HSRP Failover

[Jonathan Slack]

Hello,

I am wondering if what I am looking at is even possible and where to start as I can not find any documentation that looks like it.  I have attached a picture as well for visual representation.

Here is what I am looking to do, if possible.

I am looking at having two routers, one primary, one secondary, and two different ISPs, ISP A and ISP B.

We have our own ARIN Block and I need to setup BGP.

Fail States.

Primary Router

1. ISP A goes down and BGP Advertises routes now to ISP B.
2. ISP A comes back up and BGP Advertise routes now to ISP A

Secondary Router

1. Primary Router Hardware Failure, Secondary router Advertises Route out ISP A
2. ISP A goes down and BGP Advertises routes now to ISP B. (While Primary Router is down)
3. ISP A comes back up and BGP Advertise routes now to ISP A. (While Primary Router is down

Any guidance or link to a configuration document I might have missed would be very helpful or any different suggestions on a way to do achieve what I am looking for. (Possibly advertise out both ISP A and ISP B on the Primary router at the same time? Then just worry about hardware failover).  Something like that.

I have not worked with BGP in anything other then a lab environment at this time and any suggestions or documentation would be very helpful.

Thank you in advance.

[eduardopozo56]

If there any specific reason for not advertising routes to both ISP from Both routers at the same time? (Maybe load balancing between ISP?)
BGP adjacency, convergence and route propagation on internet takes time, so having the kind of failover that you need would take some seconds (maybe minutes), or hours, depending on your ISP.

I would have both routers advertising the ARIN block to both ISP's at the same time, and if you want to use only 1 ISP and the #2 just in case on failure, you can use some AS_PATH prepend on one router so the 1st one has a shorter as_path and is preferred over #2

Using this you would accomplish the following:
- Primary router would always be entry point for your ARIN block ( Shorter AS_PATH), traffic would be load-balanced between ISP_A and ISP_B depending on their inter connectivity with others ISP

- If ISP_A go down, ISP_B would take all the traffic and viceversa

- If Router1 goes down, Router2 would take all the traffic, as it was already advertising the ARIN block but with a longer AS_PATH

This is a simple way of doing it.