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Take a public subnet into two smaller public subnets

I have a cable provider who is providing a /28 let's say 200.100.50.0  Can I effectively take that subnet and break it into two smaller?  Basically I would like to host Internet for a tennant in my building however let them use their own firewall and block.

So in essense

Network 1 200.100.50.0 /29

Network 2 200.100.50.8 /29

What is the easiest way to configure my router for this setup?  We'll say Fa0/0 is the public connection, Fa0/1 is Network 1, and Fa0/2 is network 2.

If that is not possible can I break it into the following....

200.100.50.0 /30 (i.e .1 is the service provider, .2 is my router)

200.100.50.4 /30 (Goes to one customer's firewall)

200.100.50.8 /29 (Goes to my firewall)

What would be the best way to handle this setup?

1 REPLY
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Re: Take a public subnet into two smaller public subnets

ngthen@moonark.com

I have a cable provider who is providing a /28 let's say 200.100.50.0  Can I effectively take that subnet and break it into two smaller?  Basically I would like to host Internet for a tennant in my building however let them use their own firewall and block.

So in essense

Network 1 200.100.50.0 /29

Network 2 200.100.50.8 /29

What is the easiest way to configure my router for this setup?  We'll say Fa0/0 is the public connection, Fa0/1 is Network 1, and Fa0/2 is network 2.

If that is not possible can I break it into the following....

200.100.50.0 /30 (i.e .1 is the service provider, .2 is my router)

200.100.50.4 /30 (Goes to one customer's firewall)

200.100.50.8 /29 (Goes to my firewall)

What would be the best way to handle this setup?

You can break up the address space however you want because the provider will simply route the /28 to you. What you do with it is up to you but be aware that when you start splitting it up you will lose available addresses because of the network and broadcast address for each subnet.

If your router connects to the ISP using part of the /29 address space and you then want to use the same /29 address space for your firewall and the customers firewall you will need to do the 2 x /30 + 1 x /29. It would be more efficient if your provider could provide you a separate /30 just for the connection between your router and theirs and then you can use 2 x /29 for you and your customer.

Jon

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