CCNP / BSCI Test Tutorial: Route Summarization As well as OSPF Null Interface
CCNP exam accomplishment, significantly to the BSCI exam, requires you understand the small print of route summarization. This talent not simply demands that you've a comfort stage with binary conversions, but You should understand how and exactly where to apply route summarization with Just about every specific protocol.
You also have to grasp the “Unwanted effects” of route summarization. With OSPF, there'll truly be an additional interface made at the point of summarization, which catches lots of CCNP candidates unexpectedly. Let’s Have a look at the null0 interface and how it relates to OSPF summarization.
On R1, the following networks are redistributed into OSPF, and then summarized.
interface Loopback16
ip deal with 16.sixteen.16.sixteen 255.0.0.0
interface Loopback17
ip handle seventeen.17.seventeen.seventeen 255.0.0.0
interface Loopback18
ip deal with 18.eighteen.eighteen.eighteen 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 related subnets
R1(config-router)#summary-address sixteen.0.0.0 252.0.0.0
The summary deal with appears on R2, a downstream router.
R2#present ip route ospf
O E2 16.0.0.0/six [a hundred and ten/twenty] by way of 172.12.123.1, 00:00:05, Serial0
Enable’s return to R1 and check out its OSPF table.
R1#show ip route ospf
O 16.0.0.0/6 is really a summary, 00:01:fifty one, Null0
Where did the null0 interface originate from, and why could it be there? Packets despatched into the null interface are dropped, and In this instance, that’s a fantastic factor.
Once you configure summary routes in OSPF, a path to null0 are going to be installed to the OSPF routing table. This helps to circumvent routing loops. Any packets destined with the routes which were summarized could have a longer match from the routing table, as proven below…
C seventeen.0.0.0/8 is specifically linked, Loopback17
C 16.0.0.0/eight is specifically related, Loopback16
C 19.0.0.0/8 is directly related, Loopback19
C 18.0.0.0/eight is instantly linked, Loopback18
O sixteen.0.0.0/6 is actually a summary, 00:01:51, Null0
.. and packets that don't match among the summarized routes but do match the summary route will be dropped.
Avoiding routing loops when doing route redistribution and summarization is significant. OSPF offers us a bit help in 토토 that regard in this case, and when you analyze more intricate redistribution scenarios on your own technique to the CCNP and CCIE, you’ll understand that we’ll consider all the help we might get!
