CCNP / BSCI Exam Tutorial: Route Summarization Along with the OSPF Null Interface
CCNP Test achievements, particularly on the BSCI Examination, needs you understand the details of route summarization. This skill not merely calls for you have a convenience amount with binary conversions, but you have to know how and in which to use route summarization with Every person protocol.
You even have to be aware of the “Unwanted side effects” of route summarization. With OSPF, there will essentially be an additional interface developed at The purpose of summarization, and this catches a lot of CCNP candidates by surprise. 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, and after that summarized.
interface Loopback16
ip address sixteen.16.16.sixteen 255.0.0.0
interface Loopback17
ip tackle seventeen.17.17.17 255.0.0.0
interface Loopback18
ip address eighteen.eighteen.eighteen.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 related subnets
R1(config-router)#summary-address sixteen.0.0.0 252.0.0.0
The summary address appears on R2, a downstream router.
R2#clearly show ip route ospf
O E2 sixteen.0.0.0/6 [a hundred and ten/twenty] through 토토사이트 172.twelve.123.one, 00:00:05, Serial0
Allow’s go back to R1 and take a look at its OSPF desk.
R1#display ip route ospf
O 16.0.0.0/6 is a summary, 00:01:fifty one, Null0
Exactly where did the null0 interface originate from, and why can it be there? Packets despatched towards the null interface are dropped, and In this instance, that’s a good matter.
Whenever you configure summary routes in OSPF, a path to null0 will be put in in to the OSPF routing desk. This helps to prevent routing loops. Any packets destined for that routes which were summarized will have an extended match within the routing desk, as shown underneath…
C seventeen.0.0.0/8 is instantly linked, Loopback17
C sixteen.0.0.0/eight is directly related, Loopback16
C 19.0.0.0/eight is instantly related, Loopback19
C 18.0.0.0/8 is instantly related, Loopback18
O sixteen.0.0.0/6 is a summary, 00:01:fifty one, Null0
.. and packets that don't match one of several summarized routes but do match the summary route are going to be dropped.
Preventing routing loops when doing route redistribution and summarization is vital. OSPF presents us somewhat help in that regard in this situation, and as you review far more complicated redistribution scenarios on the way to the CCNP and CCIE, you’ll understand that we’ll get all the assistance we might get!