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Opposite EBGP Neighbor Receives Route and it Jitters because the Preference of IBGP is Lower than Blackhole Route

Publication Date:  2012-07-27 Views:  41 Downloads:  0
Issue Description
One MAN double-egress is square. Two NE80E and two GSR establish EBGP neignbor relation. IBGP neighbor relation is established between two NE80. Opposite EBGP neighbor GSR route normally receives the route when the first NE80E advertises MAN internal route with BGP network command. When the second NE80E advertises the same route, opposite EBGP neighbor (the second GSR) cannot normally receive the route. Check received routing list of GSR and there is increase and decrease.
Topology:
GSR --------- GSR
 |                       |
 |                       |        
NE80E(1)----NE80E(2)
Alarm Information
Null
Handling Process
Change the preference of IBGP protocol higher than NULL0 (preference 20 255 130). And then EBGP neighbor relation can normally receive MAN internal route advertised by two NE80E.
Root Cause
disp cu and it is configured with the preference of BGP protocol.   preference 20 200 130 and preference of NULL0 routing protocol
ip route-static 58.51.0.0 255.255.192.0 NULL0 preference 230 
The preference of IBGP is lower than NULL0. The second GSR first receives MAN internal route through IBGP. The route learnt through IBGP is not optimal.
Suggestions
Route learnt through IBGP is not optimal route. 

END