[j-nsp] bgp multipath confusion

Cord MacLeod cordmacleod at gmail.com
Wed Jul 15 20:22:26 EDT 2009


I guess I don't fully understand how this is supposed to work.  I have  
an ex4200 device with 4 links, 2 to each m7.  Both m7s are acting as  
route reflectors and advertising default to the ex4200.  The loopbacks  
are advertised with ISIS.  However when I check BGP's summery and my  
routing table, it seems multipath isn't working.  Any thoughts?

ex4200:
root at crs1.sc1# show
type internal;
local-address 10.0.0.31;
export next-hop-self;
multipath;
neighbor 10.0.0.13 {
     description "iBGP to edge1";
     peer-as 64554;
}
neighbor 10.0.0.14 {
     description "iBGP to edge2";
     peer-as 64554;

Table          Tot Paths  Act Paths Suppressed    History Damp  
State    Pending
inet.0                 2          1          0          0           
0          0
Peer                     AS      InPkt     OutPkt    OutQ   Flaps Last  
Up/Dwn State|#Active/Received/Accepted/Damped...
10.0.0.13          64554         30         28       0       3        
12:03 0/1/1/0              0/0/0/0
10.0.0.14          64554         58         57       0       3        
12:03 1/1/1/0              0/0/0/0


0.0.0.0/0          *[BGP/170] 00:12:36, MED 0, localpref 100, from  
10.0.0.14
                       AS path: 3561 I
                     > to 10.0.0.69 via ge-0/0/1.0
                       to 10.0.0.49 via ge-1/0/0.0
                     [BGP/170] 00:12:36, MED 0, localpref 100, from  
10.0.0.13
                       AS path: 3561 I
                     > to 10.0.0.69 via ge-0/0/1.0
                       to 10.0.0.49 via ge-1/0/0.0

.49 and .69 are both /30 link addresses on 10.0.0.13.  So the 2 links  
in place on .14 aren't showing up.

Interface             System         L State        Hold (secs) SNPA
ge-0/0/0.0            edge2.xxx      2  Up                   23  0:1f: 
12:d2:d0:db
ge-0/0/1.0            edge1.xxx      2  Up                   24  0:1f: 
12:d3:60:2
ge-1/0/0.0            edge1.xxx      2  Up                   25  0:1f: 
12:d3:60:db
ge-1/0/1.0            edge2.xxx      2  Up                   19  0:1f: 
12:d2:d0:2



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