Refer to the attachment. Site1 and Site2 are connected through R3 and R5. OSPF is run among R2, R3, R4, R5 and R6 and their interfaces are in AREA 0.
Site1 cannot access Site2 server 10.1.77.17 (The server is normal.). But it can access devices of other segments (10.1.75.206).
1、Check routing table of R3 and save it in 10.1.77.16/28 network segment. The route is active.
R3(config)# show ip routing
Destination/Mask Proto Pref Metric Nexthop Interface
10.1.77.16/28 OSPF 10 58 10.1.75.22 Serial2:0
2、On R3 tracert 10.1.77.19 and it is abnormal (tracert 10.1.77.16/28 network segment, the path and the next-hop of routing table are not consistent. It does not pass through s2:0 and cannot from E0. After it reaches 10.1.76.170, it returns local router. There is loop.), but tracert 10.1.75.206 and it is normal.
R3# tracert -a 10.1.75.21 10.1.77.19
traceroute to 10.1.77.19(10.1.77.19) 30 hops max,40 bytes packet
1 10.1.76.170 11 ms 4 ms 50 ms
2 10.1.76.171 2 ms 10.1.76.172 1 ms 10.1.76.171 4 ms
3 10.1.75.22 27 ms 10.1.77.19 23 ms 10.1.76.170 19 ms
R3# tracert -a 10.1.75.21 10.1.75.206
traceroute to 10.1.75.206(10.1.75.206) 30 hops max,40 bytes packet
1 10.1.75.22 23 ms 23 ms 22 ms
2 10.1.77.19 23 ms 23 ms 22 ms
3 10.1.75.206 27 ms 27 ms 26 ms
3、Check forwarding table and the next-hop from FIB to 10.1.77.16/28 and that in routing table are different.
4、Refresh FIB of R3 and the problem is solved.
There are many reasons. e.g. Route policy is set on the router. The next-hop inforwarding table and routing table is inconsistent.
Check whether there is route to the server on egress router of Site1. If there is the route, confirm that the nexthop in FIB and routing table is consistent or not. If there is no such route, check whether local egress router and opposite one set route policy and filter it.
1. When the device forwards packet, it checks forwarding table. The contents come from routing table. Sometimes forwarding table is abnormal, the content in forwarding table and routing table is different.
2. The command of checking forwarding table of VRP1.6.X version: R3(config)# h-kernroute；
The command of checking forwarding table of VRP3.4 version: <Quidway> display fib。
3. VRP1.6.X version has no command of refreshing forwarding table and restarting OSPF. It only has to restart router.
The command of refreshing forwarding table of VRP3.4 version: <Quidway> reset ip fast-forwarding cache。