CCNP / BSCI Examination Tutorial: Route Summarization As well as the OSPF Null Interface
CCNP Test good results, specially on the BSCI Examination, needs you comprehend the main points of route summarization. This ability don't just calls for that you have a comfort degree with binary conversions, 토토 but You must know the way and the place 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 essentially be an additional interface made at the point of summarization, which catches a great deal of CCNP candidates abruptly. Allow’s take a look at 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 sixteen.16.16.16 255.0.0.0
interface Loopback17
ip tackle seventeen.seventeen.17.seventeen 255.0.0.0
interface Loopback18
ip tackle eighteen.eighteen.18.18 255.0.0.0
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-address 16.0.0.0 252.0.0.0
The summary tackle appears on R2, a downstream router.
R2#clearly show ip route ospf
O E2 sixteen.0.0.0/6 [110/twenty] by using 172.12.123.1, 00:00:05, Serial0
Enable’s go back to R1 and take a look at its OSPF desk.
R1#demonstrate ip route ospf
O 16.0.0.0/six is usually a summary, 00:01:51, Null0
Where by did the null0 interface originate from, and why could it be there? Packets despatched into the null interface are dropped, and In such a case, that’s an excellent matter.
Whenever you configure summary routes in OSPF, a path to null0 is going to be mounted to the OSPF routing table. This helps to avoid routing loops. Any packets destined for that routes that were summarized will likely have an extended match during the routing desk, as demonstrated under…
C 17.0.0.0/eight is specifically linked, Loopback17
C 16.0.0.0/eight is instantly connected, Loopback16
C 19.0.0.0/8 is straight connected, Loopback19
C eighteen.0.0.0/eight is specifically related, Loopback18
O sixteen.0.0.0/six is actually a summary, 00:01:fifty one, Null0
.. and packets that do not match one of several summarized routes but do match the summary route will probably be dropped.
Stopping routing loops when accomplishing route redistribution and summarization is vital. OSPF provides us a little help in that regard in this example, and as you examine more elaborate redistribution scenarios in your way to the CCNP and CCIE, you’ll understand that we’ll take all the assistance we might get!