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TOPIC: Subnetting ISP block

Subnetting ISP block 13 years 1 month ago #22226

Hi all,

I have a question on how to subnet a block of IPs given to me from an ISP. My ISP has given me a x.x.x.32/27 and I want to split the block into the following networks: x.x.x.32/28 and x.x.x.48/28. The first network is being used by my perimeter devices (firewall, vpn box, etc..) and the second network is for the DMZ interface. Are there any changes that need to be made on the ISP's router/gateway?

Thanks for your help.

Re: Subnetting ISP block 13 years 4 weeks ago #22272

  • krik
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No! Your ISP will forward every packets destined to the /27 (and therefore the two /28 ) to your internet gateway
Christophe Lemaire

Re: Subnetting ISP block 13 years 4 weeks ago #22273

  • ptk
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I could very well be wrong, but unless he's putting his own router in the second subnet, won't he need the ISP to assign another IP (in the second subnet) to the router's adapter so that the second subnet will have a default gateway?
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