System information

Troubleshooting TCP/IP
Book Title
7-122
Mismatched Hello or dead
timers, E-bits (set for stub
areas), area IDs,
authentication types,
or network masks
The values set for the Hello timer and dead timer intervals, E-bits (this bit is set if
the router is configured in a stub area), area IDs, authentication types, and network
masks should all be the same throughout an OSPF area and in some cases the
entire OSPF network.
Step 1 Use the show ip ospf neighbor privileged exec command to identify the
OSPF neighbors of each router.
Step 2 If the output does not list an expected neighbor, use the
show ip ospf interface privileged exec command on the router and its
expected neighbor. Examine the Hello and dead timer interval values
configured on OSPF interfaces.
The following is an example of the show ip ospf interface command:
C7010#show ip ospf interface
[...]
Timer intervals configured, Hello 12, Dead 48, Wait 40,
Retransmit 5
Step 3
Compare the values configured for the timers on each router. If there is a
mismatch, reconfigure the timer values so that they are the same on the
router and its neighbor.
For example, to change the Hello timer interval to 10 on Ethernet
interface 0/1, enter the following commands:
C7010(config)#interface e0/1
C7010(config-if)#ip ospf hello-interval 10
The following is an overview of the ip ospf hello-interval command:
ip ospf hello-interval seconds
Syntax Description:
• seconds—Unsigned integer that specifies the interval in seconds. The
value must be the same for all nodes on a specific network. The default
is 10 seconds.
Mismatched Hello or dead
timers, E-bits (set for stub
areas), area IDs,
authentication types,
or network masks
Step 4 Use the debug ip ospf adj privileged exec command. Check the output
for mismatched values.
In the following example, there is a network mask mismatch. The mask
received from router 141.108.10.3 is 255.255.255.0, and the mask
configured on the router C4500 is 255.255.255.252:
C4500#debug ip ospf adj
OSPF: Mismatched hello parameters from 141.108.10.3
Dead R 40 C 40, Hello R 10 C 10 Mask R 255.255.255.0 C
255.255.255.252
Step 5
If mismatches are indicated in the debug output, try to resolve the
mismatch. For detailed information about configuring OSPF, see the
Cisco IOS Network Protocols Configuration Guide, Part 1.
Step 6 Perform the same steps for all these parameters. Ensure that all routers in
an area have the same area ID, check whether all routers in the area are
configured as stub routers, check whether the same authentication type is
configured for all routers, and so forth. For information on configuring
these parameters, consult the Cisco IOS Network Protocols Configuration
Guide, Part 1.
Note: Timer values are extremely important when Cisco routers interoperate with
routers from other vendors.
Possible Problem Solution