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TOPIC: Quick question on OSPF and route summarization

Quick question on OSPF and route summarization 10 years 1 month ago #17281

Hi people i just need to clarify some stuff on ospf and route summarization

Scenario:

I have Router A which is the main router that is connected to 4 other Routers namely Router B, C, D and E. Since they are all in the same OSPF area 0, it shouldnt be a problem summarizing all 4 different subnets into one on Router A rite?

Therefore, i was wondering if this command would work:

Router A(config-router)# network 192.168.1.0 0.0.0.15 area 0

Basically, i used a subnet mask of /30 for each serial connection so i would have 192.168.1.0, 192.168.1.4, 192.168.1.8 and 192.168.1.12. By using the above command, does it summarize all 4 networks into one? Or is it advisable to specify 4 commands for each respective serial link? Please advise.
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Re: Quick question on OSPF and route summarization 10 years 1 month ago #17325

  • Dove
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what I understood is you had give the below subnetwor to all the routers serial interfaces respectively. if its correct then

Yep, It will work but you gotta give this command in all the 4 routers. so there is no sense to use this wildcard

It will be helpful if you wanna route more then one sub-network from a router then you can use like this. That is if you want to route aall the 4 sub-network what you have mentioned in a single routing command then this statment
Router A(config-router)# network 192.168.1.0 0.0.0.15 area 0

will help you.

Hope I answered to your query.

Dove
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Re: Quick question on OSPF and route summarization 10 years 1 month ago #17326

Hi Dove,

thanks for your reply. What you are saying is if i were to use the command :

Router A(config-router)# network 192.168.1.0 0.0.0.15 area 0

Then all my other routers are required to use the above command as well???

But if i were to use the following commands :

Router A(config-router)# network 192.168.1.0 0.0.0.3 area 0
Router A(config-router)# network 192.168.1.4 0.0.0.3 area 0
Router A(config-router)# network 192.168.1.8 0.0.0.3 area 0
Router A(config-router)# network 192.168.1.12 0.0.0.3 area 0

This would mean that configurations on other routers would be required to enter the subnet for only its own serial interface?

Thanks in advance!
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Re: Quick question on OSPF and route summarization 10 years 1 month ago #17329

  • Dove
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what I mean to say is you can use, its not a mandatory.

Exact command is this one only based on the subnet what you had given on serial interface.
Router A(config-router)# network 192.168.1.0 0.0.0.3 area 0

Dove
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Re: Quick question on OSPF and route summarization 10 years 1 month ago #17353

  • S0lo
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Router A(config-router)# network 192.168.1.0 0.0.0.15 area 0

I tried something similar. It works, but I had to issue the same command on other routers too.
Studying CCNP...

Ammar Muqaddas
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