NE40 connects with MA5200F. User adds one C address pool (xxx.11.77.0) on MA5200F and enables roundtrip route on NE40. Parts of routes on NE40 are as follows:
ip route-static xxx.11.76.0 255.255.254.0 NULL 0 preferenc 60
ip route-static xxx.11.76.0 255.255.255.0 xxx.11.78.242 preferenc 60
ip route-static xxx.11.77.0 255.255.255.0 xxx.11.78.242 preference 60
The user deletes ip route-static xxx.11.76.0 255.255.254.0 NULL 0 preferenc 60
Most users can dial, but cannot access network.
1. Tracer route and it cannot reach MA5200F.
2. Tracert xxx.11.76.0 to NE40 from external network and it is unreachable.
3. NE40 route is not advertised.
4. Check NE40 configuration and BGP is as follows:
network xxx.11.76.0 255.255.254.0
5. network xxx.11.76.0 255.255.254.0 advertises 23-bit mask route of xxx.11.76.0, but ip route-static xxx.11.76.0 255.255.254.0 NULL 0 preference60 is added when these addresses of network segment are not used. In order to advertise the route of these networks, it enables blackhole route by deceiving BGP. Delete this blackhole route, NE40 has no 23-bit mask route of xxx.11.76.0. However, if the route of configured network segment with network command is imported in BGP, the route must be in routing table. Opposite device cannot learn it and the service interrupts. Delete these three routes and add one
ip route-static xxx.11.76.0 255.255.254.0 xxx.11.78.242 preference 60. xxx.11.76.0 255.255.254.0 and route advertised by BGP network are consistent. The opposite can learn the route of 76,77 and the service recovers.
The route is problematic.