CCNP / BSCI Exam Tutorial: Route Summarization As well as OSPF Null Interface
CCNP Examination good results, particularly to the BSCI Test, calls for you recognize the main points of route summarization. This skill don't just necessitates that you have a consolation amount with binary conversions, but It's important to understand how and where to use route summarization with Each individual particular person protocol.
You even have to understand the “Unwanted side effects” of route summarization. With OSPF, there will essentially be an additional interface established at the point of summarization, which catches lots of CCNP candidates without warning. Permit’s Look into the null0 interface And the way it pertains to OSPF summarization.
On R1, the following networks are redistributed into OSPF, and after that summarized.
interface Loopback16
ip deal with sixteen.sixteen.sixteen.sixteen 255.0.0.0
interface Loopback17
ip tackle seventeen.seventeen.17.seventeen 255.0.0.0
interface Loopback18
ip deal with 18.18.eighteen.18 255.0.0.0
interface Loopback19
ip handle 19.19.19.19 255.0.0.0
R1(config)#router ospf one
R1(config-router)#redistribute linked subnets
R1(config-router)#summary-deal with 16.0.0.0 252.0.0.0
The summary address seems on R2, a downstream router.
R2#display ip route ospf
O E2 sixteen.0.0.0/6 [110/twenty] by way of 토토사이트 172.12.123.1, 00:00:05, Serial0
Allow’s go back to R1 and have a look at its OSPF table.
R1#exhibit ip route ospf
O 16.0.0.0/six is usually a summary, 00:01:fifty one, Null0
Wherever did the null0 interface come from, and why could it be there? Packets sent into the null interface are dropped, and In this instance, that’s a superb point.
If you configure summary routes in OSPF, a path to null0 might be installed into the OSPF routing table. This assists to prevent routing loops. Any packets destined for your routes which have been summarized may have an extended match from the routing desk, as demonstrated beneath…
C 17.0.0.0/8 is immediately related, Loopback17
C sixteen.0.0.0/eight is instantly related, Loopback16
C 19.0.0.0/eight is right linked, Loopback19
C eighteen.0.0.0/eight is right linked, Loopback18
O 16.0.0.0/six can be a summary, 00:01:51, Null0
.. and packets that don't match one of many summarized routes but do match the summary route will probably be dropped.
Stopping routing loops when undertaking route redistribution and summarization is vital. OSPF gives us just a little assist in that regard in this example, and as you study more advanced redistribution scenarios in your approach to the CCNP and CCIE, you’ll realize that we’ll acquire all the assistance we might get!