CCNP / BSCI Exam Tutorial: Route Summarization Along with the OSPF Null Interface
CCNP Examination accomplishment, notably around the BSCI exam, demands you have an understanding of the main points of route summarization. This ability don't just calls for that you have a comfort and ease level with binary conversions, but You should know how and exactly where to apply route summarization with Every single particular person protocol.
You also have to understand the “side effects” of route summarization. With OSPF, there will actually be an additional interface produced at The purpose of summarization, and this catches loads of CCNP candidates by surprise. Allow’s Check out the null0 interface And just how it pertains to OSPF summarization.
On R1, the following networks are redistributed into OSPF, after 먹튀검증 which summarized.
interface Loopback16
ip tackle sixteen.16.16.sixteen 255.0.0.0
interface Loopback17
ip address seventeen.seventeen.17.seventeen 255.0.0.0
interface Loopback18
ip handle 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 connected subnets
R1(config-router)#summary-deal with 16.0.0.0 252.0.0.0
The summary deal with appears on R2, a downstream router.
R2#present ip route ospf
O E2 sixteen.0.0.0/six [one hundred ten/twenty] by using 172.12.123.one, 00:00:05, Serial0
Enable’s go back to R1 and check out its OSPF desk.
R1#exhibit ip route ospf
O 16.0.0.0/6 is actually a summary, 00:01:51, Null0
Exactly where did the null0 interface originate from, and why could it be there? Packets sent to the null interface are dropped, and In this instance, that’s an excellent point.
Any time you configure summary routes in OSPF, a path to null0 will likely be put in to the OSPF routing table. This will help to circumvent routing loops. Any packets destined to the routes that have been summarized may have a longer match inside the routing table, as demonstrated under…
C 17.0.0.0/eight is right related, Loopback17
C 16.0.0.0/8 is instantly linked, Loopback16
C 19.0.0.0/8 is instantly connected, Loopback19
C eighteen.0.0.0/8 is directly connected, Loopback18
O 16.0.0.0/six is a summary, 00:01:fifty one, Null0
.. and packets that do not match on the list of summarized routes but do match the summary route will probably be dropped.
Avoiding routing loops when performing route redistribution and summarization is vital. OSPF offers us a bit help in that regard in this situation, and as you analyze additional elaborate redistribution eventualities on the method to the CCNP and CCIE, you’ll know that we’ll acquire all the help we may get!