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Configuring the Switch
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- 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 resending link-state advertisements.
(Range: 1-65535 seconds; Default: 1)
- A router will resend an LSA to a neighbor if it receives no acknowledgment. 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.
• Hello Interval – Sets the interval between sending hello packets on an interface.
(Range: 1-65535 seconds; Default: 10)
- This interval must be set to the same value for all routers on the network.
- Using a smaller Hello interval allows changes in the network topology to be
discovered more quickly, but may result in more routing traffic.
• Rtr Dead Interval – Sets the interval at which hello packets are not seen before
neighbors declare the router down. This interval must be set to the same value for
all routers on the network. (Range: 1-65535 seconds; Default: 40, or 4 times the
Hello Interval)
• Cost – Sets the cost of sending a packet on an interface, where higher values
indicate slower ports. (Range: 1-65535; Default: 1)
- This router uses a default cost of 1 for all ports. Therefore, if you install a Gigabit
module, you need to reset the cost for all of the 100 Mbps ports to some value
greater than 1.
- Routes are subsequently assigned a metric equal to the sum of all metrics for
each interface link in the route.
• Authentication Type – Specifies the authentication type used for an interface.
(Options: None, Simple password, 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.
- 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 Authentication Key and Message Digest Key-id must be used consistently
throughout the autonomous system. (Note that the Message Digest Key-id field
is disabled when this authentication type is selected.)
• 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)