CCNP / BSCI Examination Tutorial: Route Summarization Along with the OSPF Null Interface
CCNP Test success, significantly over the BSCI exam, needs you understand the small print of route summarization. This skill not simply necessitates that you've got a comfort and ease level with binary conversions, but you have to know the way and where to apply route summarization with Each and every particular person protocol.
You even have to be aware of the “Uncomfortable side effects” of route summarization. With OSPF, there will really be an additional interface established at the point of summarization, and this catches a great deal of CCNP candidates by surprise. Enable’s Check out the null0 interface and how it pertains to OSPF summarization.
On R1, the next networks are redistributed into OSPF, after which summarized.
interface Loopback16
ip tackle sixteen.sixteen.sixteen.16 255.0.0.0
interface Loopback17
ip deal with 17.17.17.17 255.0.0.0
interface Loopback18
ip tackle eighteen.eighteen.18.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-address 16.0.0.0 252.0.0.0
The summary tackle seems on R2, a downstream router.
R2#present ip route ospf
O E2 16.0.0.0/six [one hundred ten/twenty] through 172.12.123.1, 00:00:05, Serial0
Permit’s return to R1 and have a look at its OSPF table.
R1#present ip route ospf
O 16.0.0.0/six is usually a summary, 00:01:fifty one, Null0
In which did the null0 interface come from, and why is it there? Packets sent for the null interface are dropped, and In this instance, that’s a great factor.
Once you configure summary routes in OSPF, a route to null0 will probably be put in to the OSPF routing table. This helps to forestall routing loops. Any packets destined with the routes which have been summarized can have an extended match while in the routing desk, as revealed below…
C seventeen.0.0.0/eight is straight connected, Loopback17
C 16.0.0.0/eight is immediately connected, Loopback16
C 19.0.0.0/eight is instantly related, Loopback19
C eighteen.0.0.0/8 is right connected, Loopback18
O 16.0.0.0/six is a summary, 00:01:51, Null0
.. and packets that do not match 먹튀 among the list of summarized routes but do match the summary route is going to be dropped.
Preventing routing loops when performing route redistribution and summarization is important. OSPF offers us somewhat help in that regard in this situation, and when you research a lot more advanced redistribution scenarios in your strategy to the CCNP and CCIE, you’ll realize that we’ll take all the assistance we could possibly get!