Troubleshooting the routing entry default

The OSPF database contains an LSA, but therouting table does not contain the corresponding route entry.

  Possible Causes

1) The switch configurations have problems, for example, route filtering is configured and the network types do not match.

2)The network environment has problems, for example, better routes are available.

3)When the FA address is not 0, the route is not learned from OSPF. If the FA address is not 0, the route with the smallest metric to the FA address is preferred and the route to the FA address must be an intra-domain or inter-domain OSPF route; otherwise, the route entry will be ignored.

Troubleshooting ProcedureStep1: Check switch configurations.

1.Check whether the network types match.

If the network types at the two ends of a neighbor do not match, the routing table cannot be correctly loaded.

2.Check whether route filtering is configured.

If the distribute-list in table filters routes incorrectly, the routes cannot be added the routing table (distribute-list is used to filter routes).

3.Checkwhether the routing loop prevention function is enabled.

If the loop prevention function is enabled and a VPN route carries DN-Bit or the Route Tag value of an LSA is the same as that at the local end in an L3 VPN environment,check whether the requirements for loop prevention are met.

Step2: Check the network environment.

1. Check whether better routes areavailable.

2. Check whether the routes in the routing table are better than the OSPF route, namely, the administrative distance is smaller than the OSPF route, which causes that the OSPF route cannot be added into the routing table.

3. Check whether the route to the FA addressis reachable.

When a router receives a Type7-to-Type 5 LSA, the router finds that the routing table has noroute to the FA address (not 0), which causes that the Type 5 LSA route cannot be added into the routing table.

Possible cause: Route filtering (distribute-list in) is configured, which filters the routes to the FA address.

Step3: Check the FA addresses.

For type-5 LSAs of OSPF, there are two types of FA addresses:

1) If OSPF imports anexternal route and the FA address of the generated type 5 LSA is 0.0.0.0, other routers will calculate the next-hop address of the external route by considering how to reach ASBR(namely, the router that generates the type 5 LSA) in order to reach the  external network.

2) If OSPF imports an external route and the FA address of the generated type 5 LSA is not 0, other routers will calculate the next-hop address of the external route by considering how to reach this FA address in order to reach the external network.

If all of the following conditions aremet:  

1) the egress interface of the imported external route is enabled with OSPF;

2) the egress interface of the imported external route is not passive-interface;

3) the OSPF network type for the egress interface of the imported external route is broadcast;

the FA address (not 0) of the generatedType 5 LSA is the next-hop address of the imported external route.  

Note: If the FA address is not 0, the routewith the smallest metric to the FA address is preferred and the route to the FA address must be an intra-domain or inter-domain OSPF route; otherwise, theroute entry will be ignored.  

Above all, if a Type 5 LSA route is not added into the routing table, you have two solutions:

(1) Run the show ip route | in x.x.x.x (FA address) command to check whether the learned address is an intra-domain or inter-domain address. If not, the route will not be added into the routing table.

(2) Disable OSPF on the egress interface ofthe ASBR.

Step4: Fault Information Collection

Collect log information (pay attention to the time switch and the time accuracy) for fault analysis.

[Device debugging information, configuration, hardware and software versions, device logs and operation logs]

Collecting basic information

showversion

showversion slots

showrun

showlog

show ipinterface brief

showinterface status

showinterface counter sum   

showinterface counter  rate

showinterfaces counters errors

showinterfaces counters

showarp counter

showarp

showarp detail

showmac-address-table

showmac-address-table counter

show iproute

show iproute count

showmemory

dir

showvlan

showcpu

showcpu-protect mb

showcpu-protect

show cpu-protect slot X //X indicates the slot ID, for example, slot 4 of the standalone deviceS8610:  show cpu-pro slot 4; for example,slot 4 of chassis 2 in the VSU: show cpu-pro slot 2/4

show cpu-protect slot X //X indicates the slot ID, for example, slot 4 of the standalone deviceS8610:  show cpu-pro slot 4; for example,slot 4 of chassis 2 in the VSU: show cpu-pro slot 2/4

showspanning-tree

showspanning-tree summary

Collecting OSPF information

show ipospf

show ipospf neighbor

show ipospf interface

show ipospf border-routers

show ipospf spf

show ipospf route count

show ipospf route

show ipospf database database-summary

show ipospf database

show ipospf database router

show ipospf database network

show ipospf database summary

show ipospf database asbr-summary

show ipospf database external

show ipospf database nssa-external

showmemory protocols

Collecting OSPF dynamic information

1.Ruijie#debug ip ospf route ase

Ruijie#clearip ospf ase   //(Note: This command is ahidden command.)   undebug all: disablesdebugging.

2.Ruijie#show ip route    //Check whetherthe route is available. If not, go to step 3; otherwise, stop collectinginformation.

3.Ruijie#debug ip ospf route spf

Configurethe cost value on an interface enabled with OSPF ((config-if)# mode): ip ospfcost 99

Waitfor 10 seconds.

Restorethe configuration: no ip ospf cost (If the cost value is configured originally,it is reset to ip ospf cost xxx, where xxx indicates the originally configuredvalue)

undebugall: disable debugging.

4.Ruijie#show ip route    //Check whetherthe route is available. If not, go to step 5; otherwise, stop collectinginformation.

5.Ruijie#clear ip ospf process  

6. Ruijie#show ip route   //Checkwhether the route is available.

Debugging operations cause risks (The worst case is to restart the switch for recovery). Perform debugging only after informing customers ofthe risks and get them accepted. It is recommended debugging at low-traffic periods (Be more cautious when dealing with core switches). If packet capturing is also required for troubleshooting, remember to collect information by debugging and packet capturing at the same time.