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Configuring the Open Shortest Path First Protocol (Version 2)
Transmit Delay – Sets the estimated time to send a link-state update
◆
packet over an interface. (Range: 1-65535 seconds; Default: 1 second)
LSAs have their age incremented by this delay before transmission. You
should consider both the transmission and propagation delays for an
interface when estimating this delay. Set the transmit delay according
to link speed, using larger values for lower-speed links.
If this delay is not added, the time required to transmit an LSA over the
link is not taken into consideration by the routing process. On slow
links, the router may send packets more quickly than devices can
receive them. To avoid this problem, you can use the transmit delay to
force the router to wait a specified interval between transmissions.
Retransmit Interval – Sets the time between re-sending link-state
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advertisements. (Range: 1-65535 seconds; Default: 5 seconds)
A router will resend an LSA to a neighbor if it receives no
acknowledgment after the specified retransmit interval. The retransmit
interval should be set to a conservative value that provides an
adequate flow of routing information, but does not produce
unnecessary protocol traffic. Note that this value should be larger for
virtual links.
Set this interval to a value that is greater than the round-trip delay
between any two routers on the attached network to avoid unnecessary
retransmissions.
Authentication Type – Specifies the authentication type used for an
◆
interface. (Options: None, Simple, MD5; Default: None)
Use authentication to prevent routers from inadvertently joining an
unauthorized area. Configure routers in the same area with the same
password (or key). All neighboring routers on the same network with
the same password will exchange routing data.
When using simple password authentication, a password is included in
the packet. If it does not match the password configured on the
receiving router, the packet is discarded. This method provides very
little security as it is possible to learn the authentication key by
snooping on routing protocol packets.
When using Message-Digest 5 (MD5) authentication, the router uses
the MD5 algorithm to verify data integrity by creating a 128-bit
message digest from the authentication key. Without the proper key
and key-id, it is nearly impossible to produce any message that
matches the prespecified target message digest.
The Message Digest Key ID and Authentication Key and must be used
consistently throughout the autonomous system.
◆
Authentication Key – Assign a plain-text password used by
neighboring routers to verify the authenticity of routing protocol
messages. (Range: 1-8 characters for simple password or 1-16
characters for MD5 authentication; Default: no key)
When plain-text or Message-Digest 5 (MD5) authentication is enabled
as described in the preceding item, this password (key) is inserted into
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| Unicast Routing
C
20
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