CCNP / BSCI Test Tutorial: Route Summarization As well as OSPF Null Interface
CCNP Examination accomplishment, significantly within the BSCI exam, calls for you fully grasp the details of route summarization. This talent not merely calls for that you've a ease and comfort stage with binary conversions, but You should know the way and in which to apply route summarization with Every single individual protocol.
You also have to know the “Negative effects” of route summarization. With OSPF, there'll truly be an extra interface made at the point of summarization, and this catches many CCNP candidates unexpectedly. Allow’s Look into the null0 interface and how it relates to OSPF summarization.
On R1, the next networks are redistributed into OSPF, after which summarized.
interface Loopback16
ip deal with sixteen.sixteen.sixteen.16 255.0.0.0
interface Loopback17
ip deal with 17.seventeen.seventeen.17 255.0.0.0
interface Loopback18
ip tackle 18.eighteen.eighteen.eighteen 255.0.0.0
interface Loopback19
ip tackle 19.19.19.19 255.0.0.0
R1(config)#router ospf one
R1(config-router)#redistribute related subnets
R1(config-router)#summary-deal with 16.0.0.0 252.0.0.0
The summary handle seems on R2, a downstream router.
R2#show ip route ospf
O E2 sixteen.0.0.0/six [110/20] via 172.12.123.one, 00:00:05, Serial0
Let’s return to R1 and examine its OSPF desk.
R1#show ip route ospf
O 16.0.0.0/six is really a summary, 00:01:fifty one, Null0
The place did the null0 interface come from, and why can it be there? Packets despatched on the null interface are dropped, and in this case, that’s a very good issue.
Whenever you configure summary routes in OSPF, a path to null0 might be mounted to the OSPF routing desk. This assists to avoid routing loops. Any packets destined to the routes that were summarized will likely have a longer match during the routing table, as revealed underneath…
C 17.0.0.0/8 is instantly related, Loopback17
C sixteen.0.0.0/8 is straight related, Loopback16
C 19.0.0.0/eight is specifically linked, Loopback19
C eighteen.0.0.0/8 is immediately linked, Loopback18
O sixteen.0.0.0/six is often a summary, 00:01:fifty one, Null0
.. and packets that do not match one of many summarized routes but do match the summary route are going to be dropped.
Avoiding routing loops when accomplishing route redistribution and summarization is 토토사이트 vital. OSPF gives us somewhat help in that regard in this situation, and when you analyze a lot more sophisticated redistribution scenarios in your method to the CCNP and CCIE, you’ll understand that we’ll consider all the assistance we could possibly get!