ROUTERA is connected with NET1: 172.16.0.0/24, and ROUTERC with NET2:192.168.0.0/24; ROUTERA connects to ROUTERB through the network segment of 10.0.0.0/30. ROUTERB connects to ROUTERC through 10.0.0.4/30. The interfaces that interconnect ROUTERA to ROUTERB, and ROUTERB to ROUTERC have enabled OSPF protocol, and also import direct and static routes.
The customer reports that the PC (192.168.0.2) under ROUTERC cannot ping to the PC (172.16.0.2) in the network segment of 172.16.0.0.
1. Check the gateway of PC, and it is normal.
2. Check the configuration of OSPF, and it is normal.
3. Check the routes at ROUTERA and ROUTERC, and they have learned the routes from the peer.
4. At ROUTERC, execute TRACERT for PC in 172.16.0.0/24, and it is found that packets circulate between ROUTERB and ROUTERC. It is doubted that there is a loop between ROUTERB and ROUTERCk. After checkup, ROUTERC is configured with the static route as follows: IP ROUTE 172.16.0.0 255.255.255.128 10.0.0.5(IP of ROUTERB connected to ROUTERC) PRE 60. Therefore, ROUTERB contains the route to the network segment of 172.16.0.0/24 and 172.16.0.0/25, with next hop to ROUTERA and ROUTERC respectively. According to the maximum-length matching principle, the packets to 172.16.0.0/24 will circulate between ROUTERC and ROUTERB, until TTL turns to zero and the packets are discarded. Delete the static routes at ROUTERC, and the problem is solved.
1. The configuration of gateway is problematic.
2. The configuration of OSPF is problematic.
3. The route learning is problematic.
At last, it is found that the static route configuration is false.
During the configuration, delete the unnecessary data, avoiding route loop.