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TOPIC: Supernet routing

Supernet routing 8 years 7 months ago #25730

  • NeoTech
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Hey guys, im unsure if im posting in the right place here, but i need a bit of clarification on supernetting. I cant seem to find anything related to it on the alternative menu.

now i know, using the 'ip classless' command in CISCO IOS software, global config mode, its possible to define a route to cover a range of subnets (a supernet route)

Would i be right in saying a valid supernet route for 192.168.64.0 /20 and 192.168.32.0 /20 would be 192.168.0.0 /16 :?: :?

I thought i'd nailed subnetting but im unsure of this.

regards to all and thanks in advance! :)

Neo
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Re: Supernet routing 8 years 7 months ago #25731

  • Elohim
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Well... if you don't care about what else is there in that space then that will work...

192.168.32.0/20 includes all everything from 192.168.32.0 to 192.168.47.255

192.168.64.0/20 includes everything from 192.168.64.0 to 192.168.79.255

These two /20 subnetwork doesn't really summarize well because they are not continguous. You still have another /20 between the two /20 you mention. However, if you don't care what is really there... and you just want to summarize it with one statement, 192.168.0.0/17 will summarize everything from 192.168.0.0 to 192.168.127.255 which includes the IPs you want.


Hey guys, im unsure if im posting in the right place here, but i need a bit of clarification on supernetting. I cant seem to find anything related to it on the alternative menu.

now i know, using the 'ip classless' command in CISCO IOS software, global config mode, its possible to define a route to cover a range of subnets (a supernet route)

Would i be right in saying a valid supernet route for 192.168.64.0 /20 and 192.168.32.0 /20 would be 192.168.0.0 /16 :?: :?

I thought i'd nailed subnetting but im unsure of this.

regards to all and thanks in advance! :)
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Re: Supernet routing 8 years 7 months ago #25734

  • NeoTech
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ok cheers for that. seems like ive finally got subnetting theory down but could you elaborate for me as to what you were trying to explain? did i step on some reserved addresses or something?

Thanks!

Neo
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Re: Supernet routing 8 years 7 months ago #25740

  • Chojin
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What he says,

Is you are summarizing the subnets towards 1 big subnet, but this 1 big subnet also includes ip's not in your range.

this would almost be as summarizing :

10.1.0.0 /16 and 10.2.0.0/16 towards 10.0.0.0/8 (also including the 3-254 subnets).

You don't have a 10.3.0.0/16 in above example.. but this is also included in the summarized subnet. If that doesn't matter, than your good to go :)
CCNA / CCNP / CCNA - Security / CCIP / Prince2 / Checkpoint CCSA
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Re: Supernet routing 8 years 7 months ago #25780

  • NeoTech
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Hi again chojin :), Thanks for clearing that up.

The example wasn't for anything practical it was just so i was clear i had understood supernet routing.

If im correct, using your example; supernet routing to 10.0.0.0/8 would be usable for networks 10.2.0.0/16 and 10.1.0.0/16 provided there were no other networks in the autonomous system on the 10.0.0.0/8 network... correct?

i can see how much a waste that would be though lol, so many subnets would get flooded. :shock:

Cheers!

Neo
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Re: Supernet routing 8 years 7 months ago #25781

  • NeoTech
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quick note: at time of giving that example my only intention was to cover the whole network 192.168.0.0

i realise it would cause too much traffic to be practical, but in theory wouldn't every node with 192.168.*.* designated to its ip address receive the packet?

Neo
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