User Manual UMN:CLI
V8102
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12.2.6.9 Virtual Link
In OSPF, all areas must be connected to a backbone area. If there is a break in backbone
continuity, or the backbone is purposefully portioned, you can establish a virtual link. The
virtual link must be configured in both routers.
OSPF network regards virtual link routers as Point-to-point router. Therefore, the Hello-
interval, Retransmit-interval, Transmit-delay must be consistent across all routers in an at-
tached network.
User can configure Authentication for security, Authentication key for password, and time
period for Hello-interval, Retransmit-interval, Transmit-delay and Dead-interval to operate
virtual link.
The following items describe 7 configurations for virtual link:
• Authentication
This is configuration for security of routing information. message-digest uses MD5
to encode for authentication, null means not using any of authentication.
• Authentication-key
Configures the authentication which is based on text encoding.
• Message-digest-key
Configures the authentication which is based on md5 type.
• Hello-interval
OSPF router sends Hello packet to notify existence of itself. Hello-interval is that
packet transmission interval.
• Retransmit-interval
When router transmits LSA, it is waiting for approval information come from receiver.
In this time, if there is no answer from receiver for configured time, the router trans-
mits LSA again. Retransmit-interval is configuration of the time interval between
transmission and retransmission
• Dead-interval
If there is no hello packet for the configured time. The router perceives other router is
stopped working. Dead-interval is configuration of the time interval which perceives
other router is stopped operating.
• Transmit-delay
When a router transmits LSA, the traffic can be delayed by status of communications.
Transmit-delay is considering of the configuration for LSA transmission time.
Configuration for virtual link can be selected more than 2 options without order. The fol-
lowing is explaining options of command:
• authentication [message-digest | null]
• authentication-key KEY
• message-digest-key KEY md5 KEY
• hello-interval <1-65535>
• retransmit-interval <1-65535>
• dead-interval <1-65535>
• transmit-delay <1-65535>
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