Choosing Network Addresses for new network

control

For all the real life network engineers out there...

If you are tasked with building a brand new network, how do you go logically go about deciding the class, network addresse/subnets to use? Do you have to wait until you are supplied external addresses by an ISP first then build the address space around that?

Thanks

SharkDiver

For your internal LAN, you just need to decide how many IPs and subnets you need and just pick your addresses from the RFC 1918 Private Address Spaces.

Private network - Wikipedia, the free encyclopedia

You can use these addresses at will.

SharkDiver

The ISP will assign you your inside global (internet routable) addresses that your inside local addresses (your private addresses) will be NATed to.

networker050184

I like to use /24s everywhere when using private addressing because I'm lazy! Its also nice to always have the gateway of .1. I'll usually set aside a /24 for network links and break /30s off of that.

If you are using public addressing then you just have to start chopping it up the best you can to fit your needs.

Roguetadhg

We always need more 255's in subnet masks :P