CCNP / BSCI Examination Tutorial: Route Summarization And also the OSPF Null Interface
CCNP exam good results, particularly around the BSCI Test, requires you fully grasp the main points of route summarization. This talent not merely requires that you have a comfort and ease stage with binary conversions, but You must know the way and in which to use route summarization with Each individual unique protocol.
You even have to be aware of the “side effects” of route summarization. With OSPF, there'll really be an extra interface designed at The purpose of summarization, and this catches many CCNP candidates without warning. Enable’s Examine the null0 interface And just how it pertains to OSPF summarization.
On R1, the next networks are redistributed into OSPF, and afterwards summarized.
interface Loopback16
ip deal with sixteen.16.sixteen.16 255.0.0.0
interface Loopback17
ip deal with 17.17.seventeen.17 255.0.0.0
interface Loopback18
ip deal with 18.eighteen.18.eighteen 255.0.0.0
interface Loopback19
ip handle 19.19.19.19 255.0.0.0
R1(config)#router ospf 1
R1(config-router)#redistribute related subnets
R1(config-router)#summary-deal with 16.0.0.0 252.0.0.0
The summary deal with seems on R2, a downstream router.
R2#exhibit ip route ospf
O E2 16.0.0.0/6 [one hundred ten/20] by using 172.12.123.1, 00:00:05, Serial0
Enable’s return to R1 and evaluate its OSPF table.
R1#show ip route ospf
O 16.0.0.0/six is a summary, 00:01:51, Null0
Exactly where did the null0 interface originate from, and why can it be there? Packets despatched to your null interface are dropped, and in this case, that’s an excellent matter.
Whenever you configure summary routes in OSPF, a path to null0 will be set up into your OSPF routing desk. This assists to avoid routing loops. Any packets destined to the routes that were summarized will likely have an 토토 extended match from the routing table, as proven down below…
C 17.0.0.0/8 is specifically linked, Loopback17
C sixteen.0.0.0/8 is immediately related, Loopback16
C 19.0.0.0/8 is straight connected, Loopback19
C eighteen.0.0.0/eight is straight related, Loopback18
O 16.0.0.0/six can be a summary, 00:01:fifty one, Null0
.. and packets that do not match one of the summarized routes but do match the summary route are going to be dropped.
Preventing routing loops when carrying out route redistribution and summarization is important. OSPF offers us somewhat help in that regard in this situation, and as you examine extra complex redistribution eventualities on your approach to the CCNP and CCIE, you’ll understand that we’ll take all the help we could possibly get!