CCNP / BSCI Examination Tutorial: Route Summarization Plus the OSPF Null Interface
CCNP Examination success, specially around the BSCI Examination, demands you realize the small print of route summarization. This skill not simply needs that you've got a convenience level with binary conversions, but It's important to know the way and wherever to apply route summarization with Each and 먹튀검증 every specific protocol.
You even have to understand the “Negative effects” of route summarization. With OSPF, there will in fact be an additional interface developed at the point of summarization, which catches a great deal of CCNP candidates abruptly. Permit’s Look into the null0 interface And exactly how it pertains to OSPF summarization.
On R1, the next networks are redistributed into OSPF, after which summarized.
interface Loopback16
ip handle sixteen.16.sixteen.sixteen 255.0.0.0
interface Loopback17
ip tackle seventeen.seventeen.seventeen.seventeen 255.0.0.0
interface Loopback18
ip tackle 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 one
R1(config-router)#redistribute connected subnets
R1(config-router)#summary-address sixteen.0.0.0 252.0.0.0
The summary tackle seems on R2, a downstream router.
R2#show ip route ospf
O E2 sixteen.0.0.0/6 [one hundred ten/twenty] by means of 172.twelve.123.1, 00:00:05, Serial0
Permit’s go back to R1 and examine its OSPF table.
R1#exhibit ip route ospf
O 16.0.0.0/6 is usually a summary, 00:01:fifty one, Null0
Wherever did the null0 interface originate from, and why could it be there? Packets despatched on the null interface are dropped, and In such cases, that’s an excellent matter.
If you configure summary routes in OSPF, a route to null0 will likely be put in in the OSPF routing desk. This can help to forestall routing loops. Any packets destined for your routes which were summarized will likely have a longer match in the routing table, as shown down below…
C seventeen.0.0.0/8 is immediately linked, Loopback17
C sixteen.0.0.0/8 is directly connected, Loopback16
C 19.0.0.0/8 is immediately connected, Loopback19
C 18.0.0.0/8 is specifically linked, Loopback18
O sixteen.0.0.0/six is often 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 likely be dropped.
Blocking routing loops when executing route redistribution and summarization is important. OSPF provides us just a little assist in that regard in this case, and while you review additional intricate redistribution situations on the approach to the CCNP and CCIE, you’ll understand that we’ll choose all the assistance we could get!