CCNP / BSCI Exam Tutorial: Route Summarization As well as the OSPF Null Interface
CCNP Test good results, especially around the BSCI Test, demands you fully grasp the main points of route summarization. This talent not just requires that you've a ease and comfort stage with binary conversions, but you have to know the way and in which to use route summarization with Every single specific protocol.
You even have to understand the “Unintended effects” of route summarization. With OSPF, there'll essentially be an extra interface developed at the point of summarization, and this catches a lot of CCNP candidates abruptly. Let’s Consider the null0 interface And the way it relates to OSPF summarization.
On R1, the following networks are redistributed into OSPF, after which summarized.
interface Loopback16
ip address 16.sixteen.16.sixteen 255.0.0.0
interface Loopback17
ip deal with 17.17.seventeen.17 255.0.0.0
interface Loopback18
ip deal with 18.eighteen.eighteen.18 255.0.0.0
interface Loopback19
ip address 19.19.19.19 255.0.0.0
R1(config)#router ospf one
R1(config-router)#redistribute linked subnets
R1(config-router)#summary-tackle sixteen.0.0.0 252.0.0.0
The summary tackle seems on R2, a downstream router.
R2#present ip route ospf
O E2 sixteen.0.0.0/6 [one hundred ten/twenty] by means of 172.12.123.1, 00:00:05, Serial0
Enable’s go back to R1 and check out its OSPF desk.
R1#display ip route ospf
O sixteen.0.0.0/6 is really a summary, 00:01:51, 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 such a case, that’s a great point.
Whenever you configure summary routes in OSPF, a route to null0 might be set up in the OSPF routing desk. This can help to circumvent routing loops. Any packets destined for that routes that were summarized will likely have an extended match within the routing desk, as proven below…
C seventeen.0.0.0/8 is directly connected, Loopback17
C 16.0.0.0/eight is right connected, Loopback16
C 19.0.0.0/8 is immediately linked, Loopback19
C eighteen.0.0.0/8 is specifically connected, Loopback18
O sixteen.0.0.0/6 is usually a summary, 00:01:51, Null0
.. and packets that do not match among the summarized routes but do match the summary route will be dropped.
Preventing routing 토토사이트 loops when accomplishing route redistribution and summarization is vital. OSPF offers us somewhat assist in that regard in this situation, and as you analyze much more complicated redistribution scenarios on your solution to the CCNP and CCIE, you’ll know that we’ll choose all the help we could possibly get!