Virtual Link And Transit Area For Ospf - Cisco NCS 5500 Series Configuration Manuals

Implementing OSPF
Example:
RP/0/RP0/CPU0:router(config-ospf)# timers lsa min-arrival 2
Limits the frequency that new processes of any particular OSPF Version 2 LSA can be accepted during flooding.
• The default is 1 second.
Step 7
timers lsa group-pacing seconds
Example:
RP/0/
/CPU0:router(config-ospf)# timers lsa group-pacing 1000
Changes the interval at which OSPF link-state LSAs are collected into a group for flooding.
• The default is 240 seconds.
Step 8
commit

Virtual Link and Transit Area for OSPF

In OSPF, routing information from all areas is first summarized to the backbone area by ABRs. The same
ABRs, in turn, propagate such received information to their attached areas. Such hierarchical distribution of
routing information requires that all areas be connected to the backbone area (Area 0). Occasions might exist
for which an area must be defined, but it cannot be physically connected to Area 0. Examples of such an
occasion might be if your company makes a new acquisition that includes an OSPF area, or if Area 0 itself
is partitioned.
In the case in which an area cannot be connected to Area 0, you must configure a virtual link between that
area and Area 0. The two endpoints of a virtual link are ABRs, and the virtual link must be configured in both
routers. The common nonbackbone area to which the two routers belong is called a transit area. A virtual link
specifies the transit area and the router ID of the other virtual endpoint (the other ABR).
A virtual link cannot be configured through a stub area or NSSA.
Figure 1: Virtual Link to Area 0
This figure illustrates a virtual link from Area 3 to Area 0.
Routing Configuration Guide for Cisco NCS 5500 Series Routers, IOS XR Release 6.3.x

Virtual Link and Transit Area for OSPF

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