[j-nsp] BGP load-balancing

david.roy at orange-ftgroup.com david.roy at orange-ftgroup.com
Tue Mar 24 04:11:52 EDT 2009

Do you have the load-balance per-packet enabled on your forwarding table ? 

Could you give us the output of : show route protocol bgp logical-router R5 extensive



-----Message d'origine-----
De : juniper-nsp-bounces at puck.nether.net [mailto:juniper-nsp-bounces at puck.nether.net] De la part de Aamir Saleem
Envoyé : mardi 24 mars 2009 08:42
À : juniper-nsp at puck.nether.net
Objet : [j-nsp] BGP load-balancing

Hi All,

I need your input regarding BGP loadbalancing with multipath option.

In JNCIP-M study guide, one of the requirement given in iBGP case study is to "Redistribute a summary of the RIP routes into IBGP from both r6 and r7"
and in second requiement "r5 must IBGP load-balance to the summary route representing the RIP prefixes".

After advetiseing RIP summary route ( from R6 and R7. R5 router is able to see two viable next-hops after enabling multipath in R5 ibgp group but in forwarding table of R5 shows only one path via R6 is available.

My question is:

Is only enabling multipath option will achive above mention requirement regarding BGP loadbalancing ?

As junos perform per-prefix loadbalncing by default so the iBGP case study requiremnt that "r5 must IBGP load-balance to the summary route representing the RIP prefixes" cannot be achiedved by with multipath only. All other router behind R5 router also following the same path as chosen by R5.

some output from test senario are below:

aamir at LAB1 <aamir at LAB1># run show route protocol bgp logical-router R5
inet.0: 80 destinations, 136 routes (80 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both     *[BGP/170] 01:50:49, localpref 100, from
                      AS path: I
                    > to via lt-1/2/0.116
                      to via lt-1/2/0.117
                    [BGP/170] 01:50:49, localpref 100, from
                      AS path: I
                    > to via lt-1/2/0.117 [edit] aamir at LAB1#

Forwarding table:
Logical router: R5
Routing table: inet
Destination        Type RtRef Next hop           Type Index NhRef Netif     user     0                          indr  262148     3
                                            ucst  974
7 lt-1/2/0.116

Any input is more then welcome.

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