Concept Guide

Changing OSPFv2 Parameters on Interfaces
You can modify the OSPF conguration on switch interfaces.
Some interface parameter values must be consistent across all interfaces to avoid routing errors. For example, set the same time interval
for the hello packets on all routers in the OSPF network to prevent misconguration of OSPF neighbors.
To change OSPFv2 parameters on the interfaces, use any or all of the following commands.
• Change the cost associated with OSPF trac on the interface.
CONFIG-INTERFACE mode
ip ospf cost
– cost: The range is from 1 to 65535 (the default depends on the interface speed).
• Change the time interval the router waits before declaring a neighbor dead.
CONFIG-INTERFACE mode
ip ospf dead-interval seconds
– seconds: the range is from 1 to 65535 (the default is 40 seconds).
The dead interval must be four times the hello interval.
The dead interval must be the same on all routers in the OSPF network.
• Change the time interval between hello-packet transmission.
CONFIG-INTERFACE mode
ip ospf hello-interval seconds
– seconds: the range is from 1 to 65535 (the default is 10 seconds).
The hello interval must be the same on all routers in the OSPF network.
• Use the MD5 algorithm to produce a message digest or key, which is sent instead of the key.
CONFIG-INTERFACE mode
ip ospf message-digest-key keyid md5 key
– keyid: the range is from 1 to 255.
– Key: a character string.
NOTE
: Be sure to write down or otherwise record the key. You cannot learn the key after it is congured. You must be
careful when changing this key.
NOTE: You can congure a maximum of six digest keys on an interface. Of the available six digest keys, the switches
select the MD5 key that is common. The remaining MD5 keys are unused.
• Change the priority of the interface, which is used to determine the Designated Router for the OSPF broadcast network.
CONFIG-INTERFACE mode
ip ospf priority number
– number: the range is from 0 to 255 (the default is 1).
• Change the retransmission interval between LSAs.
CONFIG-INTERFACE mode
ip ospf retransmit-interval seconds
Open Shortest Path First (OSPFv2 and OSPFv3)
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