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eBGP Load Balancing

I have an eBGP connection between two routers, I want to add another link for load balancing. The 2 new routers will run eBGP between them as well. How do I achieve load balancing between the two links. Do I need to set up any parameters, or does BGP load balance by default?

Thanks for the help, and let me know if i need to give more details

1 REPLY
Hall of Fame Super Silver

Re: eBGP Load Balancing

Hello Gary,

you need to perform some configuration to take advantage of both links.

There are two ways of doing this:

a) move the eBGP session to loopback addresses and with two static routes on each router with destination the neighbor router's loopback address

b) define a second eBGP session on the physical ip addresses of both routers and add the command maximum-paths 2 under router bgp x on both routers

a) config

R1

int loop1

ip address 1.1.1.1 255.255.255.255

desc ebgp loop

!

router bgp X

neighbor 2.2.2.2 remote-as y

neighbor 2.2.2.2 update-source loop1

neighbor 2.2.2.2 ebgp-multihop 2

!

ip route 2.2.2.2 255.255.255.255 s0/0

ip route 2.2.2.2 255.255.255.255 s0/1

the same must be done on the second router define loop1 wiht ip 2.2.2.2/32 add static routes for net 1.1.1.1/32 uing the links define in the same way the eBGP session

b) config

nothing special

config a has to be preferred because only one copy of each advertisement is received for example when you receive a full BGP internet table.

note: in this case you see only one route for each prefix but there are two routes for the eBGP next-hop and recursion provides load-balancing.

config b uses the maxim-paths and in this case you see two B routes for each prefix in the routing table.

Hope to help

Giuseppe

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