* Correction: in Point number 3 i meant 10.0.35.0/24 & not 10.0.25.0/25
________________________________ From: Narendra Naukwal <[email protected]> To: Wilberth E. Lemaître <[email protected]>; "[email protected]" <[email protected]> Sent: Friday, 26 July 2013 8:50 AM Subject: Re: [OSL | CCIE_RS] FW: OSPF Summarization 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 _______________________________________________ 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 _______________________________________________ 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
