CCNP / BSCI Examination Tutorial: Route Summarization Plus the OSPF Null Interface
CCNP Test good results, especially around the BSCI Test, requires you understand the small print of route summarization. This talent not simply necessitates that you have a consolation stage with binary conversions, but You must know the way and exactly where to use route summarization with Each individual particular person protocol.
You even have to be aware of the “side effects” of route summarization. With OSPF, there'll basically be an additional interface created at The purpose of summarization, which catches many CCNP candidates without warning. Let’s Examine the null0 interface And exactly how it relates to OSPF summarization.
On R1, the next networks are redistributed into OSPF, after which summarized.
interface Loopback16
ip deal with 16.16.sixteen.sixteen 255.0.0.0
interface Loopback17
ip address seventeen.17.17.seventeen 255.0.0.0
interface Loopback18
ip tackle 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 related subnets
R1(config-router)#summary-address 16.0.0.0 252.0.0.0
The summary deal with appears on R2, a downstream router.
R2#show ip route ospf
O E2 sixteen.0.0.0/6 [a hundred and ten/20] by using 172.twelve.123.1, 00:00:05, Serial0
Let’s go back to R1 and check out its OSPF table.
R1#clearly show ip route ospf
O sixteen.0.0.0/6 is a summary, 00:01:fifty one, Null0
In which did the null0 interface come from, and why can it be there? Packets despatched to your null interface are dropped, and In cases like this, that’s a superb thing.
When you configure summary routes in OSPF, a route to null0 will be installed into your OSPF routing table. This assists to prevent routing 먹튀 loops. Any packets destined for the routes that were summarized could have a longer match in the routing table, as revealed under…
C 17.0.0.0/eight is immediately linked, Loopback17
C 16.0.0.0/eight is specifically related, Loopback16
C 19.0.0.0/eight is instantly related, Loopback19
C 18.0.0.0/eight is right connected, Loopback18
O 16.0.0.0/six is often a summary, 00:01:fifty one, Null0
.. and packets that don't 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 important. OSPF gives us slightly assist in that regard in this example, and when you analyze much more complicated redistribution scenarios on your own method to the CCNP and CCIE, you’ll realize that we’ll consider all the assistance we may get!