BGP with 2 Routers and 2 ISPs

DPG

Does anyone have any suggestions for this setup? Any major drawbacks?

burbankmarc

Nope, pretty straight forward. Just make sure you configure it properly so you don't become a transit AS. Work with your ISPs, they'll be able to help you.

yebo2010

Just make sure that the ISPs do not inject the whole internet routing table into your routers. As also already said, make sure you are not a transit.
I assume the idea is load balancing and redundancy right? Then you have to tune your BGP carefully otherwise you may overload one link.
But the topology is possible and its good to have to 2 or more ISP connections. The routers should have enough resources though(depending on the internal network size).

ColbyG

What are the speeds of each link? Do you want to load balance or simply use one ISP for failover?

What do you have so far?

networker050184

Its a rather common design and shouldn't give you much issue. The configuration complexity depends like Colby said on what your traffic goals are. Active/backup is pretty straight forward. I've seen customers pulling their hair out for months trying to equally load balance two circuits like this though. I have one that requests at least one change a month for the last three months trying to even out the traffic. They even went with GLBP on the inside even though I tried to tell them that would make zero difference. Some guy from Cisco TAC told them it would help though, so it had to right

ColbyG

networker050184 wrote: »

Its a rather common design and shouldn't give you much issue. The configuration complexity depends like Colby said on what your traffic goals are. Active/backup is pretty straight forward. I've seen customers pulling their hair out for months trying to equally load balance two circuits like this though. I have one that requests at least one change a month for the last three months trying to even out the traffic. They even went with GLBP on the inside even though I tried to tell them that would make zero difference. Some guy from Cisco TAC told them it would help though, so it had to right

Hahaha, nice.

What have they ended up sticking with? If I were to do this, I think I'd just inject a default from each BGP router into the IGP and let it go. If I wanted active/failover I'd just set LP inbound and prepend or use communities outbound. I don't have a ton of real world BGP experience yet though.

networker050184

They haven't ended up sticking with anything yet. Right now they are still trying to equally balance their inbound traffic with prepends which isn't working out ok for them. For outbound traffic they have the other provider (which is a larger more well connected AS) prepending to them to try and balance their outbound traffic. Thats not really working out too well for them either.

What I would do is get a full table from the larger provider and local and default from the smaller provider. That way you can take the smaller provider for all their local traffic (which should also return over your link in most instances). You will then send the majority of your internet traffic through the larger provider and since that provider is larger and better connected to the net the vast majority of your inbound traffic will come in there automatically. The default route can serve as your back up solution when your full feed goes down. That is the simplest solution IMO and requires the least amount of configuration and route manipulation.

ColbyG

Ah, that makes a lot of sense.

DPG

I should make it a little more clear.

Router_A and Router_B are Cat 6500's and will take the full routing table. The 6500s will be announcing public IPs.

I will have some devices using Router_A and some Router_B. There will also be devices connected to both Router_A and Router_B.

All links are gigabit ethernet.

jason_lunde

DPG wrote: »

I should make it a little more clear.

Router_A and Router_B are Cat 6500's and will take the full routing table. The 6500s will be announcing public IPs.

I will have some devices using Router_A and some Router_B. There will also be devices connected to both Router_A and Router_B.

All links are gigabit ethernet.

How big are your pipes to both ISP's? I did read your post, but I am assuming you dont have gig speeds to both providers

DPG

I have gigabit ethernet to both providers. They will be upgraded to 10Gbit soon. I will probably be introducing another provider into the mix later this year.

The current setup is the two providers into one 6509.

ColbyG

That's pretty impressive...

If they're equal speeds, just inject defaults from each router into your IGP and let everything work.

yebo2010

I agree, that's what I could advise as well. Life seems to be straight forward in that case.