How to split up IP's

[kaptk2]

Right now I have:
Firewall<--->server<--->router1<===T1 Line===>router2<--->LAN

IP an attempting to switch from a private addressing scheme to a public one. Right now I have everything on the left side of router one has a 10.0.0.0/24 and all the LAN clients have a 10.1.0.0/24 address. What is the best way to split up my new /24 public block. I only need about /28 on the left side of router1. Any suggestions on how to split this up to keep the most IP's?

Hope that this all makes sense.

 

[chieftan999]

You need to have a good look at subnetting. It would be too long a reply to explain it on this forum.

Go to google and search subnetting.

Very basically:-

Default class C = 255.255.255.0

The above is 1 network and 254 hosts.

Subnetting borrows bits from the host portion. First legal subnet of a class C is 192 (Borrowing the first 2 bits (128 + 64). Apply the formula to the switched on bits (2 of them) and you get 4 subnets but the RFC's state you cannot have all 0's and all 1's so you have to -2 off this, which leaves you with 2 subnets. Now do the same with the switched off bits (there are 6 of them as there are 8 bits in each byte) so the maths is 2 - 4 - 8 - 16 - 32 - 64 but you cannot have all 0's and all 1's so minus 2 and you have 62. So the answer is 2 subnets with 62 hosts per subnet.

Now just continue borrowing the bits and applying the same formula and it will give you the available subnets and hosts per subnet.

This is also applied to Class B and Class A networks.

 

[kaptk2]

After some Googling here is what I found out. The best/easiest way would be to do this:

Put a /28 on top of the /24. The /28 would be on the Firewall/router side of things and the rest of the address on the LAN side of things. So routing looks like this:

Firewall/Router 192.1.0.1/28 route 192.1.0.0/24 router1 IP
(192.1.0.2)

Router1 IP 192.1.0.2/28 route 192.1.0.0/24 to router2 IP
(192.1.0.3)

Router2 IP 192.1.0.3/24 route 192.1.0.0/28 to router1 IP
(192.1.0.2)

I think this setup will work, and using it I will have 11 IP's to use for the existing server and futere servers.

Any suggestions on why this would not work or does it all make sense?

 

[chieftan999]

If you use a /28 and take up three addresses for the routers and firewall then you are correct with stating it leaves 11 addresses.

Should work okay