CCNP / BSCI Exam Tutorial: Route Summarization As well as OSPF Null Interface
CCNP exam accomplishment, notably about the BSCI Test, calls for you have an understanding of the 토토 details of route summarization. This talent not only demands that you've got a comfort and ease level with binary conversions, but You will need to understand how and wherever to use route summarization with Every single particular person protocol.
You also have to learn the “Unwanted effects” of route summarization. With OSPF, there will truly be an additional interface developed at the point of summarization, which catches a lot of CCNP candidates by surprise. Enable’s Examine the null0 interface And just how it relates to OSPF summarization.
On R1, the following networks are redistributed into OSPF, and after that summarized.
interface Loopback16
ip deal with sixteen.sixteen.16.16 255.0.0.0
interface Loopback17
ip tackle seventeen.seventeen.seventeen.17 255.0.0.0
interface Loopback18
ip address eighteen.eighteen.eighteen.18 255.0.0.0
interface Loopback19
ip address 19.19.19.19 255.0.0.0
R1(config)#router ospf 1
R1(config-router)#redistribute linked subnets
R1(config-router)#summary-handle sixteen.0.0.0 252.0.0.0
The summary deal with appears on R2, a downstream router.
R2#display ip route ospf
O E2 16.0.0.0/six [one hundred ten/twenty] by using 172.12.123.one, 00:00:05, Serial0
Let’s return to R1 and examine its OSPF table.
R1#present ip route ospf
O sixteen.0.0.0/six is often a summary, 00:01:51, Null0
Wherever did the null0 interface originate from, and why could it be there? Packets despatched for the null interface are dropped, and In this instance, that’s a great matter.
Whenever you configure summary routes in OSPF, a path to null0 are going to be set up in to the OSPF routing table. This assists to circumvent routing loops. Any packets destined for your routes which were summarized could have a longer match during the routing desk, as shown beneath…
C seventeen.0.0.0/8 is immediately linked, Loopback17
C sixteen.0.0.0/8 is straight connected, Loopback16
C 19.0.0.0/8 is immediately connected, Loopback19
C 18.0.0.0/eight is directly related, Loopback18
O sixteen.0.0.0/six can be a summary, 00:01:51, Null0
.. and packets that do not match one of many summarized routes but do match the summary route will likely be dropped.
Protecting against routing loops when carrying out route redistribution and summarization is vital. OSPF offers us a little help in that regard in this situation, and when you study extra intricate redistribution situations in your method to the CCNP and CCIE, you’ll know that we’ll choose all the help we could possibly get!