From: Wang Dehong-DWANG1 (Dehong.Wang@motorola.com)
Date: Fri Jun 24 2005 - 18:00:18 GMT-3
What are two lowest numbers for netmask? 0 is the lowest, and the next is 128. any others are greater than 128..
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Kelly Scroggins
Sent: Friday, June 24, 2005 3:37 PM
To: ccie2be
Cc: 'Stewart, Dirk'; ccielab@groupstudy.com
Subject: Re: Subnet Question? Help
Here's a great IP Subnet Calc. I know there's a ton of 'em out there, but this one uses a web interface as well as a command line (Perl) interface.
I guess the drawback is, apparently it won't let you enter the mask you wanted.
http://jodies.de/ipcalc?host=172.16.26.49&mask1=255.255.50.0&mask2=
Corrected illegal netmask: 255.255.50.0
Address: 172.16.26.49 10101100.00010000 .00011010.00110001
Netmask: 255.255.0.0 = 16 11111111.11111111 .00000000.00000000
Wildcard: 0.0.255.255 00000000.00000000 .11111111.11111111
=>
Network: 172.16.0.0/16 10101100.00010000 .00000000.00000000 (Class B)
Broadcast: 172.16.255.255 10101100.00010000 .11111111.11111111
HostMin: 172.16.0.1 10101100.00010000 .00000000.00000001
HostMax: 172.16.255.254 10101100.00010000 .11111111.11111110
Hosts/Net: 65534 (Private Internet)
-- kelly http://home1.gte.net/res0psau/index.html#Hang-Gliding-Stuff-- -- \ / \/ /\ / \ -- --
Quoting ccie2be <ccie2be@nyc.rr.com>: Dirk, It might help if you remember the function of a subnet mask - it tells a networking device which portion of the ip address belongs to the network and which portion belongs to the host. Without a netmask and assuming classless networking, how would a networking device know which portion of the ip address represents the network address and which represents the host address. For example, consider 122.189.12.196 In this ip address, which bits represent the network address? 122 ? 122.189 ? 122.189.12 ? 122.189.12.192 ? Without a subnet mask there's no way to know. It could be the first 8 bits, the first 16, the first 24 bits, and even the first 26 bits. Actually, it could be any number of bits between 8 and 31. (192 = 1100 0000 in binary) In your example, the first 2 octets (16 bits) of the net mask are 255 255. In binary, that's equal to 1111 1111 and 1111 1111. Remember that a one in the net mask means the corresponding bit of the ip address is part of the network address. So, back to your example - since the first 16 bits of the netmask are all one's, that means that the first 16 bits of your ip address are part of the network address. Now, what's 50 in binary? 50 is equal to 32 + 16 + 2 which in binary is 0011 0010. So, the problem with this is that not all the one bits in the netmask are consecutive but they have to be. IOW, when u look at a netmask in binary the first 8 bits will always be 1 and the last bit will always be zero and altogether there are 32 bits. So, the questions becomes where between the 8th bit and the 32nd bit in the netmask do the bits change from being one to being zero. Where the bits change from being one to being zero is the dividing line between the network portion and the host portion of the ip address - all the one bits on the left represent the network portion and all the zero bits on the right represent the host portion. It actually isn't all the hard once it "clicks" but it is fundamental to understanding ip networking. so, make sure you're 100% clear on this. HTH, Tim -----Original Message----- From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Stewart, Dirk Sent: Friday, June 24, 2005 3:22 PM To: ccielab@groupstudy.com Subject: Subnet Question? Help Is this a valid subnet and where and how would I use it. Does ISP use this kind of subnet.. If this is possible how much networks and host could I get from it... 172.16.26.49 255.255.50.0 ----------------------------------------------------- This message has been scanned for viruses and dangerous content for Fulton County by DefendMail, and is believed to be clean. _______________________________________________________________________ Subscription information may be found at: http://www.groupstudy.com/list/CCIELab.html _______________________________________________________________________ Subscription information may be found at: http://www.groupstudy.com/list/CCIELab.html
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