Hi Wilberth,
I would say that the most efficient summarization configuration would depend on
IP Addressing scheme used else where in your network:
For Example:
1. You could use 'area 2 range 10.0.32.0 255.255.248.0' on the ABR.
10.0.32.0/21 would cover range 10.0.32.1 to 10.0.39.255. This one liner summary
will solve your purpose, however, it will include subnets that do not belong to
your IP scheme like (10.0.35.0, 10.0.37.0, 10.0.38.0, 10.0.39.0). You can use
this summary address if these subnets are NOT being used at a different place
in your network. Also this can be used in case there are more specific routes
to these prefixes.
--> Routing table will have an entry like: {O IA 10.0.32.0/21
[110/11] via 12.0.0.2, 00:00:11, FastEthernet0/1}
2. You could use 'area 2 range 10.0.32.0 255.255.252.0' on the ABR. This would
cover range from 10.0.32.1 to 10.0.35.254. This still includes 10.0.35.0/24
subnet!! You can use this summary address if prefix 10.0.35.0/24 is NOT being
used at a different place in your network. Also this can be used in case there
is more specific route to the prefix (10.0.35.0/24)
--> Routing table will have an entry like: O IA 10.0.32.0/22
[110/11] via 12.0.0.2, 00:00:18, FastEthernet0/1
O IA
10.0.36.0/24 [110/11] via 12.0.0.2, 00:00:05, FastEthernet0/1
3. If you are using 10.0.25.0/25 network some place else in your network & do
not want this to be a part of your summary range you could use 'area 2 range
10.0.32.0 255.255.254.0'. This consists of 10.0.32.1 - 10.0.33.254.
Your routing table after summarization would look like:
O IA 10.0.34.0/24 [110/11] via 12.0.0.2, 00:00:13, FastEthernet0/1
O IA 10.0.32.0/23 [110/11] via 12.0.0.2, 00:00:04, FastEthernet0/1
O IA 10.0.36.0/24 [110/11] via 12.0.0.2, 00:02:47, FastEthernet0/1
Hope this helps!
Naren
________________________________
From: Wilberth E. Lemaître <[email protected]>
To: "[email protected]" <[email protected]>
Sent: Friday, 26 July 2013 5:25 AM
Subject: [OSL | CCIE_RS] FW: OSPF Summarization
I was able to see the logic, if I use 3 bits the ranges would go like these:
10.0.0.0 - 10.0.31.255
10.0.32.0 - 10.0.63.255
10.0.64.0 - 10.0.95.255
As we can see, they will all catch in the second range. Correct me if I am
wrong?
From: [email protected]
To: [email protected]
Subject: OSPF Summarization
Date: Thu, 25 Jul 2013 17:27:49 -0600
Hello community,
I have a question in regards summarization.
Let's say I have area 2 configured on a router, the advertised networks are the
following:
router ospf xxx
network 10.0.32.1 0.0.0.0 area 2
network 10.0.33.1 0.0.0.0 area 2
network 10.0.34.1 0.0.0.0 area 2
network 10.0.36.1 0.0.0.0 area 2
network 192.168.0.2 0.0.0.0 area 0
I want to summarize area 2, the mechanism I use for summarization is the
following and correct me if I am wrong. I look for the octet where the decimal
number changes, or where the bits are not equal. As we can see this happens on
the 3rd octet and I start using increments with each octet value:
128 64 32 16 8 4 2 1
I wonder myself which increment or which number would catch all of those into
one advertisement counting from zero, in other words, how many binary digits I
have to convert to 1 in order to do the summarization.
Based on this scenario, 32 would catch less than what we need, 64 would be the
perfect one, and I will need to convert only 2 bits (the first 2 bits) and my
subnet mask would look like 11111111.11111111.11000000.00000000 and the network
range would go like this:
10.0.0.0 - 10.0.63.255
10.0.64.0- 10.0.127.255
As we can see, if I use a subnet mask of 18, I will be including ranges that
are NOT necessary.
What would be the efficient summarization in order to accomplish this scenario?
Please explain ;)
Best regards,
Wilberth
_______________________________________________
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_______________________________________________
For more information regarding industry leading CCIE Lab training, please visit
www.ipexpert.com
Are you a CCNP or CCIE and looking for a job? Check out
www.PlatinumPlacement.com
http://onlinestudylist.com/mailman/listinfo/ccie_rs
