CCNP / BSCI Exam Tutorial: Route Summarization Plus the OSPF Null Interface
CCNP exam achievement, particularly to the BSCI Examination, demands you fully grasp the main points of route summarization. This ability don't just needs that you've a comfort and ease level with binary conversions, but You should understand how and in which to use route summarization with Just about every person protocol.
You even have to know the “Uncomfortable side effects” of route summarization. With OSPF, there'll actually be an extra interface developed at the point of summarization, and this catches many CCNP candidates abruptly. Allow’s Examine the null0 interface and how it relates to OSPF summarization.
On R1, the following networks are redistributed into OSPF, and afterwards summarized.
interface Loopback16
ip deal with sixteen.sixteen.16.sixteen 255.0.0.0
interface Loopback17
ip address 17.17.seventeen.seventeen 255.0.0.0
interface Loopback18
ip handle eighteen.18.eighteen.eighteen 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-handle 16.0.0.0 252.0.0.0
The summary deal with seems on R2, a downstream router.
R2#display ip route ospf
O E2 sixteen.0.0.0/six [a hundred and ten/twenty] by using 172.12.123.one, 00:00:05, Serial0
Permit’s return to 먹튀검증 R1 and evaluate its OSPF desk.
R1#clearly show ip route ospf
O 16.0.0.0/six is a summary, 00:01:fifty one, Null0
Where by did the null0 interface come from, and why is it there? Packets despatched for the null interface are dropped, and In cases like this, that’s an excellent detail.
Any time you configure summary routes in OSPF, a route to null0 will likely be mounted into your OSPF routing table. This will help to stop routing loops. Any packets destined for that routes which have been summarized may have an extended match during the routing table, as demonstrated beneath…
C seventeen.0.0.0/8 is directly related, Loopback17
C 16.0.0.0/eight is straight connected, Loopback16
C 19.0.0.0/eight is right related, Loopback19
C 18.0.0.0/8 is directly related, Loopback18
O 16.0.0.0/6 is usually a summary, 00:01:fifty one, Null0
.. and packets that don't match one of several summarized routes but do match the summary route might be dropped.
Blocking routing loops when doing route redistribution and summarization is vital. OSPF offers us a bit assist in that regard in this case, and while you analyze far more advanced redistribution eventualities with your method to the CCNP and CCIE, you’ll recognize that we’ll just take all the assistance we could possibly get!