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.
GSR --------- GSR
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.
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 188.8.131.52 255.255.192.0 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.
Route learnt through IBGP is not optimal route.