ebgp multihop

[nabhishek]

Hi

I have 2 routers connected via 2 serial links. To enable load balancing between the two i have configured EBGP using the loopback ips.

routerA

ip loopback lo 1.1.1.1 255.255.255.255

router bgp 64001

neighbor 2.2.2.2 remote-as 64002

neighbor 2.2.2.2 update-source loopback0

routerB

ip loopback lo 2.2.2.2 255.255.255.255

router bgp 64002

neighbor 1.1.1.1 remote-as 64001

neighbor 1.1.1.1 update-source loopback0

The loopbacks are reachable using static routes(not shown).

To enable load balancing between the 2 is it required to use ebgp-multihop command on both the routers?

If so why?

[Jon Marshall]

Hi

You will need to do 2 things

1) Enable ebgp multihop. This is because EBGP assumes that the neighbour is on a directly connected interface. if it isn't and in this case it isn't you need to tell EBGP that the neighbour interface is more than one hop away ie.

ebgp-multihop 2

2) You will also need to tell BGP to use multiple paths if you want load balancing to work. Attached is a link to a doc that explains this in detail.

http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a0080094431.shtml

HTH

Jon

[guruprasadr]

HI, [Pls rate if HELPS]

Configure as below:

Router A:

neighbor 2.2.2.2 ebgp-multihop

!!You must configure eBGP multihop whenever the external BGP (eBGP) connections are not on the same network address

Router B:

neighbor 1.1.1.1 ebgp-multihop

Using "show ip route" verify the Load Balancing across both the Paths.

Pls Refer the Link below (for help):

http://www.cisco.com/en/US/tech/tk365/technologies_configuration_example09186a00800945bf.shtml#conf1

PLS Rate if HELPS

Best Regards,

Guru Prasad R