when you summarize the 172.16.0.0 range why do you go for /22 and not /21? /22 gives you 4 hosts, but don't you need to subtract 2 (broadcast and network) hosts leaving you with only 2 available hosts?
OSPF LSA Type 3 summarization
Scenario:
The mineral express is specialized in trading expensive minerals. You are their senior network engineer and responsible for the OSPF network that they have running. One of your colleagues is complaining that the routing table is becoming too large. It's up to you to configure some summarization!
Goal:
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- Router Talc and Fluorite have multiple loopback interfaces. Configure the network so Area 0 only sees a summary of these networks. Use the most optimal summary.
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IOS:
c3640-jk9s-mz.124-16.bin
Topology:
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Comments (5)
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ReneMolenaar 2012-06-18 12:33:28We are summarising networks so you don't have to worry about a network or broadcast address.
These are the networks:
Code:172.16.0.0/24
172.16.1.0/24
172.16.2.0/24
172.16.3.0/24I can combine 172.16.0.0/24 + 172.16.1.0/24 into 172.16.0.0/23
And we can combine 172.16.2.0/24 and 172.16.3.0/24 into 172.16.2.0/23
172.16.0.0/23 and 172.16.2.0/23 can be combined into 172.16.0.0/22 together.
If you are a bit fuzzy about this...try the following:
Write down 172.16.0.0/24,172.16.1.0/24, 172.16.2.0/24 and 172.16.3.0/24 in binary below each other...then draw a line where the bits are the same. You'll see that the first 22 bits are the same for these 4 networks so that's the summary we can use.
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WezVR 2012-06-19 13:44:06Thanks Rene, I understand the concepts was just confused about the network and broadcast addresses and whether or not you had to take them into consideration.
ReneMolenaar wrote:We are summarising networks so you don't have to worry about a network or broadcast address.
These are the networks:
Code:172.16.0.0/24
172.16.1.0/24
172.16.2.0/24
172.16.3.0/24
I can combine 172.16.0.0/24 + 172.16.1.0/24 into 172.16.0.0/23
And we can combine 172.16.2.0/24 and 172.16.3.0/24 into 172.16.2.0/23
172.16.0.0/23 and 172.16.2.0/23 can be combined into 172.16.0.0/22 together.
If you are a bit fuzzy about this...try the following:
Write down 172.16.0.0/24,172.16.1.0/24, 172.16.2.0/24 and 172.16.3.0/24 in binary below each other...then draw a line where the bits are the same. You'll see that the first 22 bits are the same for these 4 networks so that's the summary we can use.
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ReneMolenaar 2012-06-19 16:03:35
alright
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gass 2013-04-07 11:40:18Strangely when I studied for my CCNA, my instructor always used to tell me how multi-area OSPF in CCNP was the hardest thing to grasp of all the material. So far EIGRP has been much more unpredictable and unintuitive for me with all those metrics and feasibility conditions and second-hand routing information. I find OSPF to be neat and logical. And the labs are easy to complete.
Thank you Rene for all the work you've done for us. Currently studying for my CCNP ROUTE using your book.