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IPv6 Training (Cisco): Using the “area range” Command 

Added: 01/07/2009, Hits: 4,007, Rating: 0, Comments: 0, Votes: 0
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The “area range” command is a Cisco IOS “Router” configuration command; that is used to consolidate and summarize routes at an OSPF area boundary.

Another way of explaining is, the “area range” command is a Cisco IOS “Router” configuration command; that is performed (used) only on OSPF Area Border Routers or (ABRs), so the ABRs can perform “route summarization” for an OSPF area.

Now, just in case you’re new to the concept of an ABR performing “Route Summarization”; ABR “Route Summarization” is the process in which an OSPF Area Border Router (ABR) advertises a single summarized route to another External ABR; and the single summarized route that is advertised by the ABR, represents the address range of the particular OSPF area(s) that the advertising ABR belong too.

Here’s an example of the command prompt and the correct syntax for the command:

Router(config-router)#area area-id range ipv6-prefix /prefix-length [advertise | not-advertise] [cost cost]

Now, in order to remove the specified area from the software configuration on an ABR, use the no area area-id command (with no other keywords). Like you see in the example below:

Router(config-router)#no area 1

Remember, when using the no area area-id command, the command removes all area options, such as area default-cost, area nssa, area range, area stub, and area virtual-link.

The “area range” command Keywords and Arguments Explained:

area-id – This argument is an identifier of the area for which routes are to be summarized. The identifier can be specified as either a decimal value or an IPv6 prefix.

ipv6-prefix —This argument is (represents) the IPv6 prefix.

/prefix-length — This argument is (represents) the IPv6 prefix length.

advertise – This optional keyword sets the address range status to advertise and generates a Type 3 summary link-state advertisement (LSA).

not-advertise – This optional keyword sets the address range status to Do Not Advertise. This means the Type 3 summary LSA is suppressed, and the component networks remain hidden from other networks.

cost – This optional keyword represents the metric or cost for the summary route, which is used during OSPF SPF calculation to determine the shortest paths to the destination. The value can be 0 to 16777215.

I hope this article was very informative and helped you quickly understand the usage, keywords, and arguments of the “area encryption” command. If you need to learn more about the command; I suggest you visit my website, were you’ll find the latest information regarding Cisco IPv6 Design and Implementation Techniques.

To your success,

Charles Ross
CCNP #CSCO10444244

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