Come on Dazza, get people really confused now and tell how supernetting works. thanks, George Vieira Network Administrator Citadel Computer Systems P/L http://www.citadelcomputer.com.au -----Original Message----- From: DaZZa [mailto:[EMAIL PROTECTED]] Sent: Monday, 17 July 2000 11:41 AM To: [EMAIL PROTECTED] Cc: [EMAIL PROTECTED] Subject: Re: [SLUG] IP Addressing/Subnetting The Easy Way... On Mon, 17 Jul 2000, Dean Hamstead wrote: > > You actually have 16 addresses in this range, with 14 useable. IP > > numbering starts from ZERO - in other words, ZERO is a valid IP address - > > so your range is from 0 to 15 - with 0 being the network address, and 15 > > being the broadcast address. > > when you use a subnet like 255.255.255.240 which 14 address's can be > used? > with 255.255.255.0 is all 255 in the last byte, eg 192.168.0.x > > with 255.255.255.240 is it the last 14 address's? > can i use it to take a chunk from the middle? > eg. 192.168.0.15 - 30? The short answer is - yes. The long answer is - with caveats. Generally, when using private addressing, subnetting is a waste of time unless you've got 1) Multiple sites or 2) Extremely complex networking Subnetting is only really useful for public networking which connects to the net - and even then, you need pretty specialised circumstances to use it. Basically, with a .240 subnet mask, for every 16 IP addresses, you can use the middle 14 - in other words, you can do this IP range Useable addresses ---------------------------------------- 0-15 1-14 16-31 17-30 32-47 33-46 48-63 49-62 You get the idea. However, you have to be logical - you can't just take a chunk here, and a chunk there - if you _really_ need 14 node segments, then take then from the early part of the subnet range, and make them contiguous - don't use, say, the 0-15 range for one segment, then say the 112-127 range for the next - because _ALL_ the unused addresses between .0 and .127 are wasted unless you apply similar 14 host networks in this range {or another multiple which will fit - a 30 host network in the 64-95 range, maybe}. Basically, non contiguous networks are wasteful of addresses - subnet masking is wasteful of addresses - anything except the base class netmask is wasteful of addreses. :-) Unless you have a specific reason for subnetting this far, don't do it - all it does is make your router work harder, and unless your network is over 50 or 60 nodes [per physical segment], you're wasting your time. DaZZa -- SLUG - Sydney Linux User Group Mailing List - http://slug.org.au/ More Info: http://slug.org.au/lists/listinfo/slug -- SLUG - Sydney Linux User Group Mailing List - http://slug.org.au/ More Info: http://slug.org.au/lists/listinfo/slug
