CCNP / BSCI Examination Tutorial: Route Summarization And The OSPF Null Interface
CCNP exam accomplishment, particularly on the BSCI Test, needs you recognize the small print of route summarization. This talent not merely needs that you have a ease and comfort amount with binary conversions, but You will need to understand how and exactly where to apply route summarization with Each individual person protocol.
You even have to find out the “Uncomfortable side effects” of route summarization. With OSPF, there'll really be an additional interface established at the point of summarization, and this catches lots of CCNP candidates without warning. Enable’s take a look at the null0 interface And exactly how it pertains to OSPF summarization.
On R1, the next networks are redistributed into OSPF, then summarized.
interface Loopback16
ip address sixteen.sixteen.sixteen.16 255.0.0.0
interface Loopback17
ip handle 17.seventeen.seventeen.17 255.0.0.0
interface Loopback18
ip address 18.18.18.eighteen 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 linked subnets
R1(config-router)#summary-tackle sixteen.0.0.0 252.0.0.0
The summary tackle seems on R2, a downstream router.
R2#display ip route ospf
O E2 16.0.0.0/6 [110/twenty] by using 172.twelve.123.1, 00:00:05, Serial0
Permit’s go back to R1 and evaluate its OSPF desk.
R1#display ip route ospf
O 16.0.0.0/6 can be a summary, 00:01:51, Null0
Wherever did the null0 interface come from, and why can it be there? Packets sent on the null interface are dropped, and In such a case, that’s a good point.
Whenever you configure summary routes in OSPF, a route to null0 will probably be put in in to the OSPF routing table. This can help to prevent routing loops. Any packets destined for the routes which were summarized can have a longer match in the routing table, as demonstrated below…
C seventeen.0.0.0/eight is directly connected, Loopback17
C 16.0.0.0/eight is straight linked, Loopback16
C 19.0.0.0/eight is directly related, Loopback19
C eighteen.0.0.0/eight is right linked, Loopback18
O sixteen.0.0.0/6 is often a summary, 00:01:51, Null0
.. and packets that don't match one of many summarized routes but do match the summary route will likely be dropped.
Stopping routing loops when undertaking route redistribution and summarization is vital. OSPF presents us a little assist in that regard in this case, and as you examine much more intricate redistribution situations with your solution to the CCNP and CCIE, you’ll know that we’ll acquire all 먹튀 the help we may get!