CCNP / BSCI Examination Tutorial: Route Summarization Along with the OSPF Null Interface
CCNP Test achievements, particularly within the BSCI Test, calls for you understand the main points of route summarization. This ability not merely involves that you've got a ease and comfort level with binary conversions, 토토사이트 but You will need to know the way and in which to use route summarization with Each individual person protocol.
You also have to know the “Unwanted effects” of route summarization. With OSPF, there will basically be an additional interface produced at the point of summarization, and this catches lots of CCNP candidates unexpectedly. Permit’s take a look at the null0 interface And exactly how it pertains to OSPF summarization.
On R1, the following networks are redistributed into OSPF, then summarized.
interface Loopback16
ip handle 16.16.16.sixteen 255.0.0.0
interface Loopback17
ip handle 17.17.seventeen.17 255.0.0.0
interface Loopback18
ip address eighteen.18.18.18 255.0.0.0
interface Loopback19
ip deal with 19.19.19.19 255.0.0.0
R1(config)#router ospf 1
R1(config-router)#redistribute connected subnets
R1(config-router)#summary-tackle 16.0.0.0 252.0.0.0
The summary handle appears on R2, a downstream router.
R2#display ip route ospf
O E2 16.0.0.0/6 [one hundred ten/20] via 172.12.123.one, 00:00:05, Serial0
Allow’s return to R1 and have a look at its OSPF table.
R1#present ip route ospf
O 16.0.0.0/six is really a summary, 00:01:fifty one, Null0
Exactly where did the null0 interface come from, and why can it be there? Packets sent towards the null interface are dropped, and In this instance, that’s an excellent thing.
Whenever you configure summary routes in OSPF, a path to null0 will probably be put in in the OSPF routing desk. This can help to forestall routing loops. Any packets destined to the routes that have been summarized will likely have an extended match within the routing table, as revealed below…
C seventeen.0.0.0/eight is immediately related, Loopback17
C 16.0.0.0/eight is directly connected, Loopback16
C 19.0.0.0/8 is immediately linked, Loopback19
C eighteen.0.0.0/8 is directly connected, Loopback18
O 16.0.0.0/six is really a summary, 00:01:51, Null0
.. and packets that do not match on the list of summarized routes but do match the summary route are going to be dropped.
Protecting against routing loops when undertaking route redistribution and summarization is significant. OSPF offers us a little bit help in that regard in this situation, and as you examine additional sophisticated redistribution eventualities with your method to the CCNP and CCIE, you’ll know that we’ll get all the help we might get!