CCNP / BSCI Exam Tutorial: Route Summarization As well as OSPF Null Interface
CCNP Test accomplishment, significantly on the BSCI Test, demands you realize the small print of route summarization. This ability not merely requires that you've got a comfort stage with binary conversions, but You must understand how and where by to use route summarization with Just about every unique protocol.
You also have to know the “Unwanted effects” of route summarization. With OSPF, there will truly be an extra interface created at the point of summarization, which catches a lot of CCNP candidates without warning. Enable’s take a look at 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 tackle sixteen.16.16.sixteen 255.0.0.0
interface Loopback17
ip deal with seventeen.seventeen.seventeen.seventeen 255.0.0.0
interface Loopback18
ip tackle eighteen.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 16.0.0.0 252.0.0.0
The summary handle seems on R2, a downstream router.
R2#present ip route ospf
O E2 먹튀검증 16.0.0.0/6 [one hundred ten/20] by means of 172.12.123.1, 00:00:05, Serial0
Permit’s go back to R1 and examine its OSPF table.
R1#present ip route ospf
O sixteen.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 cases like this, that’s an excellent issue.
If you configure summary routes in OSPF, a path to null0 will probably be installed in to the OSPF routing table. This allows to avoid routing loops. Any packets destined for that routes which have been summarized may have an extended match inside the routing desk, as shown beneath…
C 17.0.0.0/8 is directly connected, Loopback17
C sixteen.0.0.0/8 is specifically connected, Loopback16
C 19.0.0.0/8 is specifically connected, Loopback19
C 18.0.0.0/8 is directly related, Loopback18
O sixteen.0.0.0/six is usually a summary, 00:01:fifty one, Null0
.. and packets that don't match one of the summarized routes but do match the summary route will likely be dropped.
Stopping routing loops when performing route redistribution and summarization is important. OSPF presents us somewhat assist in that regard in this situation, and as you research additional advanced redistribution scenarios with your strategy to the CCNP and CCIE, you’ll understand that we’ll consider all the assistance we might get!