ebgp multihop

Unanswered Question
Jul 15th, 2007
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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?


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Jon Marshall Sun, 07/15/2007 - 23:07
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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 Sun, 07/15/2007 - 23:17
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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

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