Cisco CCNP BSCI Exam Tutorial Using OSPF s Summary-Address Command

MRR and PLR Articles Pack

Below is a MRR and PLR article in category Computers Technology -> subcategory Computer Certification.

Title:
Cisco CCNP / BSCI Exam Tutorial: Using OSPF's "Summary-Address" Command

Word Count:
339

Summary:
Success on the BSCI exam and working with OSPF in production networks can depend on you knowing the proper usage of the "summary-address" command. Learn how to use this command and see it in action with Chris Bryant, CCIE #12933.


Keywords:
ospf, summary, address, command, route, summarization, summarize, bsci, exam, pass, free, tutorial


Article Body:
BSCI exam success, not to mention earning your CCNP, can come down to your OSPF route summarization skills. There are a few different commands and situations you need to be ready for, and one of these situations is the proper use of the "summary-address" command.

The summary-address command should be used on an ASBR in order to summarize routes that are being injected into the OSPF domain via redistribution. In the following example, four routes are being redisitributed into OSPF on R1, making R1 an ASBR.

interface Loopback16

ip address 16.16.16.16 255.0.0.0

!

interface Loopback17

ip address 17.17.17.17 255.0.0.0

!

interface Loopback18

ip address 18.18.18.18 255.0.0.0

!

interface Loopback19

ip address 19.19.19.19 255.0.0.0

R1(config)#router ospf 1

R1(config-router)#redistribute connected subnets

These four routes are seen on downstream router R2 as External Type-2, the default for routes redistributed into OSPF.

R2#show ip route ospf

O E2 17.0.0.0/8 [110/20] via 172.12.123.1, 00:00:07, Serial0

O E2 16.0.0.0/8 [110/20] via 172.12.123.1, 00:00:07, Serial0

O E2 19.0.0.0/8 [110/20] via 172.12.123.1, 00:00:07, Serial0

O E2 18.0.0.0/8 [110/20] via 172.12.123.1, 00:00:07, Serial0

To summarize networks learned by redistribution, use the OSPF command summary-address. You can probably do this summarization in your head, but do so before continuing with the lab.

R1(config)#router ospf 1

R1(config-router)#summary-address 16.0.0.0 252.0.0.0

Look at the change in R2's OSPF table.

R2#show ip route ospf

O E2 16.0.0.0/6 [110/20] via 172.12.123.1, 00:00:05, Serial0

The external routes have been successfully summarized. Note that the summary route is still marked as an E2 route.

There's an interesting route installed into R1's OSPF table as well.

R1#show ip route ospf


O 16.0.0.0/6 is a summary, 00:01:51, Null0

When you configure summary routes in OSPF, a route to null0 will be installed into the OSPF routing table. This helps to prevent routing loops. Any packets destined for the routes that have been summarized will have a longer match in the routing table....

C 17.0.0.0/8 is directly connected, Loopback17

C 16.0.0.0/8 is directly connected, Loopback16

C 19.0.0.0/8 is directly connected, Loopback19

C 18.0.0.0/8 is directly connected, Loopback18


O 16.0.0.0/6 is a summary, 00:03:10, Null0

O 12.0.0.0/6 is a summary, 00:07:53, Null0

.. and packets that do not match one of the summarized routes but do match the summary route will be dropped.




You can find an AI generated version of this article here: Cisco CCNP BSCI Exam Tutorial Using OSPF s Summary-Address Command.

You can browse and read all the articles for free. If you want to use them and get PLR and MRR rights, you need to buy the pack. Learn more about this pack of over 100 000 MRR and PLR articles.

“MRR and PLR Article Pack Is Ready For You To Have Your Very Own Article Selling Business. All articles in this pack come with MRR (Master Resale Rights) and PLR (Private Label Rights). Learn more about this pack of over 100 000 MRR and PLR articles.”