Configuring OSPF Areas
22-14 Configuring OSPFv2
Configuring Area Virtual-Link Authentication
An area virtual-link can be configured for simple authentication. Neighbor virtual link routers
must have the same password.
Use the area virtual-link authentication-key command in OSPF router configuration command
mode to configure simple authentication on this area virtual-link. The key is an alphanumeric
string of up to 8 characters.
Configuring Area Virtual-Link Timers
The following timers can be configured for an area virtual-link:
•Dead-interval using the area virtual-link dead-interval command.
The dead interval specifies the number of seconds that a router must wait to receive a hello
packet before declaring the neighbor as “dead” and removing it from the OSPF neighbor list.
This value must be the same for all virtual links attached to a certain subnet. The value can
range from 1 to 8192.
• Hello-interval using the area virtual-link hello-interval command.
The hello interval specifies the number of seconds between hello packets on the virtual link.
This value must be the same for all virtual links attached to a network. The value can range
from 1 to 8192.
• Retransmit-interval using the area virtual-link retransmit-interval command.
The retransmit interval specifies the number of seconds between successive retransmissions of
the same LSAs. Valid values are greater than the expected amount of time required for the
update packet to reach and return from the interface, and range from 1 to 8192. Default is 5
seconds.
• Transmit-delay using the area virtual-link transmit-delay command.
The transmit delay specifies the estimated number of seconds before a link state update
packet on the interface should be transmitted. Valid values range from 1 to 8192. Default is 1
second.
See “Configuring OSPF Interface Timers” on page 22-16 for an OSPF timers discussion.
Configuring Route Redistribution
Redistribution permits the importation of other routing protocols into OSPF such as RIP, as well as
static and directly connected routes. See “Configuring a Not So Stubby Area (NSSA)” on
page 22-11 for an example of redistribution of connected and RIP routes by an ASBR in an NSSA
context.
Use the redistribute command in OSPF router configuration command mode to permit the
redistributions of OSPF, RIP, static, or connected routes by this router.
Configuring Passive Interfaces
Passive interfaces explicitly allows the network to be advertised, but prevents it from forming
neighbor relationships on that interface. Passive interfaces are included in the OSPF route table.
Note: RFC 2328 specifies that the retransmit-interval should be greater than the expected round-
trip delay between the two routers. Since this may be hard to estimate for a virtual link, it is better to
err on the side of making it too large.
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