CCNP / BSCI Examination Tutorial: Route Summarization And The OSPF Null Interface
CCNP exam success, specially over the BSCI exam, requires you understand the details of route summarization. This skill not simply demands you have a ease and comfort stage with binary conversions, but You must understand how and wherever to use route summarization with Every person protocol.
You also have to be aware of the “Unwanted effects” of route summarization. With OSPF, there'll essentially be an extra interface created at The purpose of summarization, which catches loads of CCNP candidates by surprise. Let’s Have a look at the null0 interface And the way it relates to OSPF summarization.
On R1, the subsequent networks are redistributed into OSPF, and after that summarized.
interface Loopback16
ip deal with 16.sixteen.sixteen.sixteen 255.0.0.0
interface Loopback17
ip deal with 17.17.seventeen.seventeen 255.0.0.0
interface Loopback18
ip address eighteen.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-tackle 16.0.0.0 252.0.0.0
The summary handle appears on R2, a downstream router.
R2#clearly show ip route ospf
O E2 sixteen.0.0.0/6 [one hundred ten/20] through 172.12.123.1, 00:00:05, Serial0
Enable’s go back to R1 and check out its OSPF table.
R1#present ip route ospf
O sixteen.0.0.0/six is really a summary, 00:01:fifty one, Null0
In which did the null0 interface come from, and why can it be there? Packets sent to your null interface are dropped, and in this case, that’s a good matter.
After you configure summary routes in OSPF, a route to null0 will probably be set up to the OSPF routing desk. This assists to stop routing loops. Any packets destined for the routes which have been summarized should have an extended match within the routing table, as revealed down below…
C 17.0.0.0/eight is instantly related, Loopback17
C sixteen.0.0.0/eight is directly connected, Loopback16
C 19.0.0.0/eight is straight connected, Loopback19
C 18.0.0.0/8 is directly connected, Loopback18
O sixteen.0.0.0/6 is often a summary, 00:01:51, Null0
.. and packets that do not match on the list of summarized routes but do match the summary route will be dropped.
Stopping routing loops when carrying out route 토토사이트 redistribution and summarization is important. OSPF gives us a bit help in that regard in this example, and while you research a lot more complicated redistribution eventualities on the solution to the CCNP and CCIE, you’ll realize that we’ll consider all the help we could get!