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Multihoming with multiple ISPs and two locations

network_user
Level 1
Level 1

My network has two offices with each office multihoming to two ISPs, with default route to ISPs. Each office has two edge routers with outbound traffic load balancing. When one of the routers/ISP goes down it has a static route (with higher weight 253) to other router to failover all the traffic. Now we are setting up a satellite link between the two offices and I want that if both the ISPs of one site goes down, that site should route all its traffic from ISP on the other site, and vice versa( For eg: in the diagram if ISP1 and ISP2 goes down, Site 1 should route its traffic from either ISP3/ISP4 through R3/R4). Attached is the general diagram of the network.

Satellite link will not be up all the time. It will be brought up only when needed.

What I have already in place on each of the 4 routers:

1. Receiving BGP default route from respective ISP.

2. Static route with higher weight(253) to failover router, to go through 2nd ISP on the same site.

What I am planning to add to make this work:

advertise site 1 IP subnets into BGP of site 2 routers with higher prepends.

add a static route for these networks in site 2 routers with tracking Satellite link, and next hop satellite link

add a default route with higher weight in site 1 routers with next hop to Satellite link

Same thing on the routers on site 2.

Will this design work?

I know that BGP will not advertise the networks of other site unless satellite link comes up as I have a condition that the static route comes up only when satellite link is up. Will BGP advertise these networks when the static route comes up in routing table, or will I have to do clear BGP soft out each time?

Thank you.

1 Reply 1

paolo bevilacqua
Hall of Fame
Hall of Fame

Yes, it will. With a proper coonfiguration you don't have to do anything under any event.

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