Cisco CCNP / BSCI Examination Tutorial: OSPF Router Varieties
Once you’re getting ready to pass the BSCI examination on the best way to the coveted Cisco CCNP certification, you will be quickly overwhelmed by the sheer amount of BGP and OSPF knowledge you have to exhibit a mastery of. One set of particulars that some BSCI and CCNP candidates underestimate are the differences between the OSPF router types.
An OSPF Internal router has one rule – it must have all its interfaces in a single area. It doesn’t imply that area has to be Space 0.
An OSPF Backbone router is a router with a minimum of a single area in the OSPF spine area, Area 0. A router can be both an Inner and Spine router if all its interfaces are in Space 0.
An Area Border Router has at the very least one interface in Space zero and another interface in a non-backbone area. ABRs are additionally considered one of two router varieties that can carry out OSPF route summarization. (To promote a summary route from one OSPF space to a different, use the area range command on the ABR.)
Lastly, an ASBR is an OSPF router that is performing route redistribution by injecting routes from one other supply into the OSPF domain. This is the other OSPF router sort that can perform route summarization; to summarize routes being redistributed into OSPF, use the summary-handle command on the ASBR.
There are a number of commands you should utilize to determine the router sorts in a given OSPF area. The command “show ip ospf” will display quite a bit of information relating to the local router, and this consists of whether or not that router is performing as an ABR or ASBR. To see the routes to the ABRs and ASBRs from the local router, run “show ip ospf border-routers”.
Getting ready to cross the BSCI exam and earn your Cisco CCNP? Route summarization is simply one of the many expertise you’ll need to grasp as a way to earn your CCNP. Whether or not it’s RIP version 2, OSPF, or EIGRP, the BSCI exam will demand that you can flawlessly configure route summarization.
Route summarization isn’t simply important for the BSCI exam. It’s a beneficial skill to have in the true world as well. Correctly summarizing routes can lead to smaller routing tables that are nonetheless capable of route packets accurately – what I wish to name “concise and complete” routing tables.
The first talent you’ve got to have in order to work with route summarization is binary math more particularly, you have to be able to take a number of routes and give you both an abstract route and masks to advertise to downstream routers. Given the networks 100.16.0.zero /16, 100.17.0.zero /16, 100.18.0.0 /16, and 100.19.0.0 /16, might you quickly give you both the abstract deal with and masks? All it’s worthwhile to do is break the four network numbers down into binary strings. We all know the final two octets will all convert to the binary string 00000000, so in this article we’ll solely illustrate the right way to convert the primary and second octet from decimal to binary.
one hundred sixteen = 01100100 00010000
a hundred 17 = 01100100 00010001
100 18 = 01100100 00010010
a hundred 19 = 01100100 00010011
To provide you with the summary route, just work from left to right and draw a line the place the four networks no longer have a bit in common. For these four networks, that time comes between the 14th and 15th bits. This leaves us with this string: 01100100 000100xx. All you need to do is convert that string back to decimal, which provides us one hundred for the first octet and sixteen for the second. (The two x values are bits on the precise aspect of the road, which aren’t utilized in calculating the abstract route.) Since we know that zero is the worth for the final octets, the resulting summary community quantity is 100.16.0.0.
However we’re not carried out! We now need to come up with the summary mask to advertise together with the abstract route. To arrive at the abstract route, write out a masks in binary with a “1” for every bit to the left of the line we drew beforehand, and a “0” for every bit to the right. That gives us the following string:
11111111 11111100 00000000 00000000
Changing that to dotted decimal, we arrive on the summary mask 255.252.0.0. The right summary community and mask to promote are 100.16.0.zero 252.0.0.0.
For the BSCI exam, emphasis is put on realizing how you can promote these abstract routes in RIPv2, EIGRP, and OSPF. For RIP v2 and EIGRP, route summarization occurs on the interface degree – it isn’t configured underneath the protocol. On the interface that should advertise the summary route, use the command “ip abstract-handle”. Listed below are examples of how the above abstract route would be configured on ethernet0 in both RIPv2 and EIGRP.
R1(config-if)ip summary-deal with rip 100.16.0.zero 255.252.0.zero
R1(config-if)ip summary-handle eigrp a hundred 100.16.0.zero 255.252.0.0
The primary distinction between the 2 is that the EIGRP command must specify the AS quantity – that’s what the “100” is in the course of the EIGRP command. Since RIPv2 does not use AS numbers, there isn’t any further worth needed within the configuration.
For OSPF, the instructions differ. In case you’re configuring inter-area route summarization, use the “space range” command. The quantity following “area” is the area containing the routes being summarized, not the area receiving the summary.
R1(config)router ospf 1
R1(config-router)area 1 vary 100.16.0.zero 255.252.0.0
If you are summarizing routes which are being redistributed into OSPF, use the abstract-handle command under the OSPF routing process on the ASBR.
R1(config)router ospf 1
R1(config-router)abstract-address 100.16.0.0 255.252.0.0
I speak from expertise when I tell you that practice makes perfect on the BSCI examination, particularly with binary and summarization questions. The beauty of these questions is that there are not any gray areas with these questions – you both know learn how to do it or you don’t. And with practice and a mind for detail, you possibly can grasp these skills, go the examination, and turn out to be a CCNP. Here is to your success on these powerful Cisco certification exams!
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