CCNP / BSCI Examination Tutorial: Route Summarization And The OSPF Null Interface
CCNP Examination results, significantly to the BSCI Test, requires you understand the main points of route summarization. This skill don't just involves that you've a comfort and ease stage with binary conversions, but You should understand how and in which to use route summarization with each individual protocol.
You even have to be aware of the “Unwanted side effects” of route summarization. With OSPF, there will actually be an additional interface created at the point of summarization, and this catches lots of CCNP candidates unexpectedly. Enable’s Look into the null0 interface and how it relates to OSPF summarization.
On R1, the following networks are redistributed into OSPF, and then summarized.
interface Loopback16
ip handle 16.sixteen.16.16 255.0.0.0
interface Loopback17
ip handle seventeen.seventeen.17.seventeen 255.0.0.0
interface Loopback18
ip address 18.eighteen.18.eighteen 255.0.0.0
interface Loopback19
ip address 19.19.19.19 255.0.0.0
R1(config)#router ospf one
R1(config-router)#redistribute connected subnets
R1(config-router)#summary-handle 16.0.0.0 252.0.0.0
The summary handle seems on R2, a downstream 먹튀 router.
R2#clearly show ip route ospf
O E2 sixteen.0.0.0/six [one hundred ten/20] through 172.twelve.123.one, 00:00:05, Serial0
Allow’s go back to R1 and check out its OSPF table.
R1#present ip route ospf
O 16.0.0.0/six is usually a summary, 00:01:fifty one, Null0
Where by did the null0 interface originate from, and why could it be there? Packets despatched towards the null interface are dropped, and in this case, that’s a fantastic point.
After you configure summary routes in OSPF, a path to null0 might be installed into the OSPF routing table. This will help to stop routing loops. Any packets destined for your routes which have been summarized will likely have a longer match from the routing desk, as shown underneath…
C 17.0.0.0/8 is right related, Loopback17
C 16.0.0.0/eight is immediately linked, Loopback16
C 19.0.0.0/eight is right related, Loopback19
C eighteen.0.0.0/8 is right related, Loopback18
O sixteen.0.0.0/6 is really a summary, 00:01:51, Null0
.. and packets that don't match among the summarized routes but do match the summary route might be dropped.
Avoiding routing loops when carrying out route redistribution and summarization is vital. OSPF gives us a little assist in that regard in this example, and when you review much more advanced redistribution eventualities on your own way to the CCNP and CCIE, you’ll recognize that we’ll take all the assistance we could get!