CCNP / BSCI Exam Tutorial: Route Summarization As well as the OSPF Null Interface
CCNP Examination achievements, specifically about the BSCI Test, requires you comprehend the small print of route summarization. This ability don't just demands that you've a convenience amount with binary conversions, but You need to know the way and the place to apply route summarization with Every individual protocol.
You even have to learn the “Unwanted side effects” of route summarization. With OSPF, there will basically be an additional interface designed at The purpose of summarization, and this catches lots of CCNP candidates unexpectedly. Permit’s Consider the null0 interface And the way it relates to OSPF summarization.
On R1, the following networks are redistributed into OSPF, after which you can summarized.
interface Loopback16
ip deal with sixteen.sixteen.16.sixteen 255.0.0.0
interface Loopback17
ip handle seventeen.17.seventeen.seventeen 255.0.0.0
interface Loopback18
ip handle 18.18.18.18 255.0.0.0
interface Loopback19
ip tackle 19.19.19.19 255.0.0.0
R1(config)#router ospf 1
R1(config-router)#redistribute related subnets
R1(config-router)#summary-address sixteen.0.0.0 252.0.0.0
The summary address seems on R2, a downstream router.
R2#show ip route ospf
O E2 16.0.0.0/six [one hundred ten/20] through 172.twelve.123.one, 00:00:05, Serial0
Let’s return to R1 and evaluate its OSPF desk.
R1#display ip route ospf
O sixteen.0.0.0/six is usually a summary, 00:01:fifty one, Null0
The place did the null0 interface come from, and why is it there? Packets sent into the null interface are dropped, and In such a case, that’s a great detail.
After you 먹튀검증 configure summary routes in OSPF, a route to null0 are going to be mounted to the OSPF routing table. This will help to forestall routing loops. Any packets destined to the routes which were summarized may have a longer match inside the routing desk, as proven underneath…
C 17.0.0.0/eight is straight linked, Loopback17
C 16.0.0.0/8 is specifically connected, Loopback16
C 19.0.0.0/8 is straight linked, Loopback19
C eighteen.0.0.0/8 is right connected, Loopback18
O 16.0.0.0/6 can be a summary, 00:01:51, Null0
.. and packets that do not match one of several summarized routes but do match the summary route are going to be dropped.
Protecting against routing loops when carrying out route redistribution and summarization is vital. OSPF gives us slightly assist in that regard in this case, and while you study extra elaborate redistribution scenarios on your approach to the CCNP and CCIE, you’ll recognize that we’ll acquire all the assistance we will get!