CCNP / BSCI Exam Tutorial: Route Summarization Along with the OSPF Null Interface
CCNP Test achievement, particularly around the BSCI Examination, demands you understand the details of route summarization. This ability not merely needs that you've got a comfort degree with binary conversions, but You must know the way and where to use route summarization with Every individual protocol.
You even have to be aware of the “side effects” of route summarization. With OSPF, there'll basically be an extra interface designed at The purpose of summarization, which catches a lot of CCNP candidates unexpectedly. Let’s Examine the null0 interface and how it pertains to OSPF summarization.
On R1, the next 먹튀 networks are redistributed into OSPF, then summarized.
interface Loopback16
ip address sixteen.16.16.16 255.0.0.0
interface Loopback17
ip handle 17.17.seventeen.seventeen 255.0.0.0
interface Loopback18
ip tackle eighteen.eighteen.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-address 16.0.0.0 252.0.0.0
The summary address appears on R2, a downstream router.
R2#present ip route ospf
O E2 sixteen.0.0.0/6 [one hundred ten/20] by way of 172.12.123.one, 00:00:05, Serial0
Enable’s return to R1 and evaluate its OSPF table.
R1#show ip route ospf
O 16.0.0.0/six is usually a summary, 00:01:fifty one, Null0
Where by did the null0 interface originate from, and why could it be there? Packets sent on the null interface are dropped, and In such a case, that’s a good matter.
Any time you configure summary routes in OSPF, a route to null0 might be mounted into the OSPF routing desk. This assists to stop routing loops. Any packets destined with the routes that have been summarized should have an extended match inside the routing table, as shown beneath…
C 17.0.0.0/eight is directly related, Loopback17
C 16.0.0.0/8 is instantly related, Loopback16
C 19.0.0.0/8 is immediately connected, Loopback19
C 18.0.0.0/eight is straight related, Loopback18
O sixteen.0.0.0/6 is usually a summary, 00:01:fifty one, Null0
.. and packets that do not match one of many summarized routes but do match the summary route will be dropped.
Blocking routing loops when accomplishing route redistribution and summarization is important. OSPF gives us a little help in that regard in this example, and when you research far more intricate redistribution situations on the way to the CCNP and CCIE, you’ll know that we’ll get all the help we might get!