CCNP / BSCI Exam Tutorial: Route Summarization As well as the OSPF Null Interface
CCNP exam success, significantly to the BSCI Test, calls for you comprehend the details of route summarization. This skill not merely requires you have a ease and comfort degree with binary conversions, but You need to understand how and wherever to apply route summarization with Every personal protocol.
You even have to know the “Unwanted effects” of route summarization. With OSPF, there'll in fact be an additional interface established at The purpose of summarization, which catches lots of CCNP candidates abruptly. Permit’s Check out the null0 interface And exactly how it relates to OSPF summarization.
On R1, the following networks are redistributed into OSPF, and after that summarized.
interface Loopback16
ip deal with sixteen.sixteen.sixteen.16 255.0.0.0
interface Loopback17
ip deal with 17.seventeen.17.17 255.0.0.0
interface Loopback18
ip tackle 18.eighteen.18.18 255.0.0.0
interface Loopback19
ip handle 19.19.19.19 255.0.0.0
R1(config)#router ospf one
R1(config-router)#redistribute related subnets
R1(config-router)#summary-handle 16.0.0.0 252.0.0.0
The summary address appears on R2, a downstream router.
R2#display ip route 토토사이트 ospf
O E2 sixteen.0.0.0/6 [a hundred and ten/twenty] through 172.twelve.123.one, 00:00:05, Serial0
Allow’s go back to R1 and take a look at its OSPF table.
R1#display ip route ospf
O sixteen.0.0.0/six can be a summary, 00:01:fifty one, Null0
Wherever did the null0 interface come from, and why is it there? Packets despatched for the null interface are dropped, and In this instance, that’s a very good matter.
When you configure summary routes in OSPF, a path to null0 might be set up in to the OSPF routing table. This can help to prevent routing loops. Any packets destined for your routes which were summarized will have an extended match within the routing desk, as revealed below…
C 17.0.0.0/eight is immediately related, Loopback17
C sixteen.0.0.0/eight is right connected, Loopback16
C 19.0.0.0/8 is directly connected, Loopback19
C 18.0.0.0/8 is right related, Loopback18
O 16.0.0.0/6 is usually a summary, 00:01:fifty one, Null0
.. and packets that don't match among the list of summarized routes but do match the summary route will probably be dropped.
Preventing routing loops when accomplishing route redistribution and summarization is important. OSPF gives us a little assist in that regard in this case, and when you research more complicated redistribution eventualities in your strategy to the CCNP and CCIE, you’ll know that we’ll take all the help we could get!