CCNP / BSCI Examination Tutorial: Route Summarization And also the OSPF Null Interface
CCNP Examination good results, significantly about the BSCI Test, calls for you have an understanding of the small print of route summarization. This skill don't just requires that you've a comfort and ease level with binary conversions, but You need to know the way and the place to use route summarization with Every single particular person protocol.
You even have to be aware of the “side effects” of route summarization. With OSPF, there'll essentially be an additional interface established at The purpose of summarization, which catches a lot of CCNP candidates abruptly. Let’s Have a look at the null0 interface and how it pertains to OSPF summarization.
On R1, the subsequent networks are redistributed into OSPF, then summarized.
interface Loopback16
ip tackle 16.sixteen.sixteen.sixteen 255.0.0.0
interface Loopback17
ip tackle 17.seventeen.17.seventeen 255.0.0.0
interface Loopback18
ip handle eighteen.eighteen.18.18 255.0.0.0
interface Loopback19
ip deal with 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 deal with seems on R2, a downstream router.
R2#show ip route ospf
O E2 sixteen.0.0.0/six [a hundred and ten/twenty] by using 172.12.123.1, 00:00:05, Serial0
Permit’s go back to R1 and examine its OSPF table.
R1#clearly show ip route ospf
O 16.0.0.0/six is usually a summary, 00:01:fifty one, Null0
Where did the null0 interface originate from, and why can it be there? Packets despatched into the null interface are dropped, and In such a case, that’s a good thing.
After you configure summary routes in OSPF, a route to null0 is going to be put in in to the OSPF routing table. This will help to stop routing loops. Any packets destined for that routes that have been summarized may have an extended match in the routing desk, as shown underneath…
C seventeen.0.0.0/eight is specifically linked, Loopback17
C 16.0.0.0/8 is directly related, Loopback16
C 19.0.0.0/eight is directly related, Loopback19
C 18.0.0.0/eight is straight connected, Loopback18
O sixteen.0.0.0/six is often a summary, 00:01:51, Null0
.. and packets that don't match one of many summarized routes but do match the summary route will likely be dropped.
Stopping routing 토토 loops when performing route redistribution and summarization is significant. OSPF offers us a bit help in that regard in this case, and as you examine a lot more intricate redistribution eventualities on your own way to the CCNP and CCIE, you’ll realize that we’ll just take all the assistance we might get!