Ip addressing question
Guys, While I am studying for the BSCN, I found the following question concerning IP addressing: Assuming your clients do not support subnet-zero, how many of your class C addresses are wasted by using the subnet mask of 255.255.255.192 and not using VLSM? a. 10% b. 25% c. 50% d. 75% Ther correct answere is b. Could someone clairfy this. Thank you ! ___ Send a cool gift with your E-Card http://www.bluemountain.com/giftcenter/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Ip addressing question
>From the subnet mask, you will get four subnets and they are .0 network .64 network .128 network and .192 network. If you are not going to make use of ip subnet-zero command, then you will be wasting 1/4 of the ip addresses since the 0 network won't be used which equals 25% of the total address alloted by the subnet mask. Hope this clarifies the answer. _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Ip addressing question
Could anyone explain to me why Subnet zero and the last subnet are not normally used?? I see why 2 host addresses are reserved in every subnet (network address and broadcast address), but I never understood why 2 networks are not used. What is the difference between these networks and the networks in between? Thanks in advance, Freddy _ Get your FREE download of MSN Explorer at http://explorer.msn.com _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Ip addressing question
Subnet zero is the network address that the routers uses for routing to the network and the broadcast address sends a broadcast to the entire network everytime it is used, which means it goes to all subnets. Therefore, these are not used as host addresses. They encompass the whole network. Others can probably add to this. Jennifer Cribbs = Original Message From "Fred Danson" <[EMAIL PROTECTED]> = > Could anyone explain to me why Subnet zero and the last subnet are not >normally used?? I see why 2 host addresses are reserved in every subnet >(network address and broadcast address), but I never understood why 2 >networks are not used. What is the difference between these networks and the >networks in between? > >Thanks in advance, > >Freddy > > >_ >Get your FREE download of MSN Explorer at http://explorer.msn.com > >_ >FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Have a Good Day!! Jennifer Cribbs [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Ip addressing question
>Subnet zero is the network address that the routers uses for routing to the >network and the broadcast address sends a broadcast to the entire network >everytime it is used, which means it goes to all subnets. Therefore, these >are not used as host addresses. They encompass the whole network. Others can >probably add to this. > >Jennifer Cribbs The restrictions on subnet zero and the all ones subnet are a limitation of classful routing protocols, which do not transmit a subnet mask. Without a subnet mask, what is the difference between: 10.0.0.0 (the network) 10.0.0.0 (subnet 0.0.0. of network 10) But there's no ambiguity in what a classless protocol sends: 10.0.0.0/8 10.0.0.0/16 So there's a clear problem with subnet zero in a classful environment. Restrictions on the all-ones subnet have never made as much sense, other than the conceptual ambiguity being the broadcast to: all subnets of 10.0.0.0/810.255.255.255 broadcast to 10.255.255.0/24 10.255.255.255 I've never seen the all-ones subnet actually cause problems, even with classful routing. > > >= Original Message From "Fred Danson" <[EMAIL PROTECTED]> = >> Could anyone explain to me why Subnet zero and the last subnet are not >>normally used?? I see why 2 host addresses are reserved in every subnet >>(network address and broadcast address), but I never understood why 2 >>networks are not used. What is the difference between these networks and the >>networks in between? >> >>Thanks in advance, >> > >Freddy > > _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Ip addressing question
Hey Jen, Your understanding of subnetting is a little off and your teaching is thus tainted. Here is a how subnetting and subnet zero work: Take a IP address for example:172. 16. 4. 0 Add an easy subnet mask to play with: 255.255.255.252 What subnets to we get from this combo?... First subnet= 172.16.4.4 Second subnet= 172.16.4.8 Third subnet= 172.16.4.12 ... Last subnet= 172.16.4.252 Lets examine one of the subnets: 172.16.4.4 The IP address space this subnet consumes is 172.16.4.4 through 172.16.4.7 The first and last IP addresses in the subnet range are the network address and subnet broadcast address respectively, and neither the first or last address can be used for host addressing, as is well known. This leaves two remaining addresses available for hosts on that subnet: 172.16.4.5 and 172.16.4.6 Subnet zero is that address space which is not taken up by the subnets. In our example this would be 172.16.4.1;172.16.4.2;172.16.4.3 Routers do not use subnet zero for anything unless instructed to do so and if this is the case, they will merely recognize it and route it. The broadcast address in a subnet does not see the entire network, it broadcasts only to its entire sub-network. Referring to our example once more, this would be the address 172.16.4.7 and only the two host addresses on the subnet would hear a broadcast from it. Hope this clarifies things. >From: Jennifer Cribbs <[EMAIL PROTECTED]> >Reply-To: Jennifer Cribbs <[EMAIL PROTECTED]> >To: [EMAIL PROTECTED] >Subject: RE: Ip addressing question >Date: Thu, 25 Jan 2001 10:38:38 -0500 > >Subnet zero is the network address that the routers uses for routing to the >network and the broadcast address sends a broadcast to the entire network >everytime it is used, which means it goes to all subnets. Therefore, these >are not used as host addresses. They encompass the whole network. Others >can >probably add to this. > >Jennifer Cribbs > > >= Original Message From "Fred Danson" <[EMAIL PROTECTED]> = > > Could anyone explain to me why Subnet zero and the last subnet are >not > >normally used?? I see why 2 host addresses are reserved in every subnet > >(network address and broadcast address), but I never understood why 2 > >networks are not used. What is the difference between these networks and >the > >networks in between? > > > >Thanks in advance, > > > >Freddy > > > > > >_ > >Get your FREE download of MSN Explorer at http://explorer.msn.com > > > >_ > >FAQ, list archives, and subscription info: >http://www.groupstudy.com/list/cisco.html > >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > >Have a Good Day!! >Jennifer Cribbs >[EMAIL PROTECTED] > >_ >FAQ, list archives, and subscription info: >http://www.groupstudy.com/list/cisco.html >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ Get your FREE download of MSN Explorer at http://explorer.msn.com _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Ip addressing question
I've read it five times and still can't see a subnet zero in the example. 172.16.x.x Class B address with a 255.255.255.252 subnet mask. Wouldn't subnet zero be down at 172.16.0.0 with 172.16.0.4 being the first 'non-subnet zero' address. 172.16.4.0 wouldn't be subnet zero would it? Gareth ""Frank Wells"" <[EMAIL PROTECTED]> wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Hey Jen, > Your understanding of subnetting is a little off and your teaching is thus > tainted. Here is a how subnetting and subnet zero work: > > Take a IP address for example:172. 16. 4. 0 > Add an easy subnet mask to play with: 255.255.255.252 > > What subnets to we get from this combo?... > First subnet= 172.16.4.4 > Second subnet= 172.16.4.8 > Third subnet= 172.16.4.12 > ... > Last subnet= 172.16.4.252 > > > Lets examine one of the subnets: 172.16.4.4 > The IP address space this subnet consumes is 172.16.4.4 through 172.16.4.7 > The first and last IP addresses in the subnet range are the network address > and subnet broadcast address respectively, and neither the first or last > address can be used for host addressing, as is > well known. This leaves two remaining addresses available for hosts on that > subnet: > > 172.16.4.5 and 172.16.4.6 > > Subnet zero is that address space which is not taken up by the subnets. In > our example this would be 172.16.4.1;172.16.4.2;172.16.4.3 > Routers do not use subnet zero for anything unless instructed to do so and > if this is the case, they will merely recognize it and route it. The > broadcast address in a subnet does not see the entire network, it broadcasts > only to its entire sub-network. Referring to our example once more, this > would be the address 172.16.4.7 and only the two host addresses on the > subnet would hear a broadcast from it. > > Hope this clarifies things. > > > > >From: Jennifer Cribbs <[EMAIL PROTECTED]> > >Reply-To: Jennifer Cribbs <[EMAIL PROTECTED]> > >To: [EMAIL PROTECTED] > >Subject: RE: Ip addressing question > >Date: Thu, 25 Jan 2001 10:38:38 -0500 > > > >Subnet zero is the network address that the routers uses for routing to the > >network and the broadcast address sends a broadcast to the entire network > >everytime it is used, which means it goes to all subnets. Therefore, these > >are not used as host addresses. They encompass the whole network. Others > >can > >probably add to this. > > > >Jennifer Cribbs > > > > > >= Original Message From "Fred Danson" <[EMAIL PROTECTED]> = > > > Could anyone explain to me why Subnet zero and the last subnet are > >not > > >normally used?? I see why 2 host addresses are reserved in every subnet > > >(network address and broadcast address), but I never understood why 2 > > >networks are not used. What is the difference between these networks and > >the > > >networks in between? > > > > > >Thanks in advance, > > > > > >Freddy > > > > > > > > >_ > > >Get your FREE download of MSN Explorer at http://explorer.msn.com > > > > > >_ > > >FAQ, list archives, and subscription info: > >http://www.groupstudy.com/list/cisco.html > > >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > > > >Have a Good Day!! > >Jennifer Cribbs > >[EMAIL PROTECTED] > > > >_ > >FAQ, list archives, and subscription info: > >http://www.groupstudy.com/list/cisco.html > >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > _ > Get your FREE download of MSN Explorer at http://explorer.msn.com > > _ > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: Ip addressing question
with the subnet mask of 255.255.255.252, 172.16.4.0 - 172.16.4.3 would be the 0 subnet and 172.16.4.252 - 172.16.4.255 would be the 1's subnet ? With classless routing expressing as 172.16.4.0 /30 allows the usage of both the first and last subnets ? Is it still important to worry about classfull routing ? ThanksGary At 01:06 PM 1/25/01 -0800, Frank Wells wrote: >Hey Jen, >Your understanding of subnetting is a little off and your teaching is thus >tainted. Here is a how subnetting and subnet zero work: > >Take a IP address for example:172. 16. 4. 0 >Add an easy subnet mask to play with: 255.255.255.252 > >What subnets to we get from this combo?... >First subnet= 172.16.4.4 >Second subnet= 172.16.4.8 >Third subnet= 172.16.4.12 >... >Last subnet= 172.16.4.252 > > >Lets examine one of the subnets: 172.16.4.4 >The IP address space this subnet consumes is 172.16.4.4 through 172.16.4.7 >The first and last IP addresses in the subnet range are the network address >and subnet broadcast address respectively, and neither the first or last >address can be used for host addressing, as is >well known. This leaves two remaining addresses available for hosts on that >subnet: > >172.16.4.5 and 172.16.4.6 > >Subnet zero is that address space which is not taken up by the subnets. In >our example this would be 172.16.4.1;172.16.4.2;172.16.4.3 >Routers do not use subnet zero for anything unless instructed to do so and >if this is the case, they will merely recognize it and route it. The >broadcast address in a subnet does not see the entire network, it broadcasts >only to its entire sub-network. Referring to our example once more, this >would be the address 172.16.4.7 and only the two host addresses on the >subnet would hear a broadcast from it. > >Hope this clarifies things. > > > > >From: Jennifer Cribbs <[EMAIL PROTECTED]> > >Reply-To: Jennifer Cribbs <[EMAIL PROTECTED]> > >To: [EMAIL PROTECTED] > >Subject: RE: Ip addressing question > >Date: Thu, 25 Jan 2001 10:38:38 -0500 > > > >Subnet zero is the network address that the routers uses for routing to the > >network and the broadcast address sends a broadcast to the entire network > >everytime it is used, which means it goes to all subnets. Therefore, these > >are not used as host addresses. They encompass the whole network. Others > >can > >probably add to this. > > > >Jennifer Cribbs > > > > > >= Original Message From "Fred Danson" <[EMAIL PROTECTED]> = > > > Could anyone explain to me why Subnet zero and the last subnet are > >not > > >normally used?? I see why 2 host addresses are reserved in every subnet > > >(network address and broadcast address), but I never understood why 2 > > >networks are not used. What is the difference between these networks and > >the > > >networks in between? > > > > > >Thanks in advance, > > > > > >Freddy > > > > > > > > >_ > > >Get your FREE download of MSN Explorer at http://explorer.msn.com > > > > > >_ > > >FAQ, list archives, and subscription info: > >http://www.groupstudy.com/list/cisco.html > > >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > > > >Have a Good Day!! > >Jennifer Cribbs > >[EMAIL PROTECTED] > > > >_ > >FAQ, list archives, and subscription info: > >http://www.groupstudy.com/list/cisco.html > >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > >_ >Get your FREE download of MSN Explorer at http://explorer.msn.com > >_ >FAQ, list archives, and subscription info: >http://www.groupstudy.com/list/cisco.html >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Ip addressing question
yes 172.16.4.0 thru 172.16.4.3 would be subnet zero. Neil Schneider ""Gareth Hinton"" <[EMAIL PROTECTED]> wrote in message 94qd3r$s2r$[EMAIL PROTECTED]">news:94qd3r$s2r$[EMAIL PROTECTED]... > I've read it five times and still can't see a subnet zero in the example. > 172.16.x.x Class B address with a 255.255.255.252 subnet mask. > Wouldn't subnet zero be down at 172.16.0.0 with 172.16.0.4 being the first > 'non-subnet zero' address. > 172.16.4.0 wouldn't be subnet zero would it? > > Gareth > > ""Frank Wells"" <[EMAIL PROTECTED]> wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > Hey Jen, > > Your understanding of subnetting is a little off and your teaching is thus > > tainted. Here is a how subnetting and subnet zero work: > > > > Take a IP address for example:172. 16. 4. 0 > > Add an easy subnet mask to play with: 255.255.255.252 > > > > What subnets to we get from this combo?... > > First subnet= 172.16.4.4 > > Second subnet= 172.16.4.8 > > Third subnet= 172.16.4.12 > > ... > > Last subnet= 172.16.4.252 > > > > > > Lets examine one of the subnets: 172.16.4.4 > > The IP address space this subnet consumes is 172.16.4.4 through 172.16.4.7 > > The first and last IP addresses in the subnet range are the network > address > > and subnet broadcast address respectively, and neither the first or last > > address can be used for host addressing, as is > > well known. This leaves two remaining addresses available for hosts on > that > > subnet: > > > > 172.16.4.5 and 172.16.4.6 > > > > Subnet zero is that address space which is not taken up by the subnets. > In > > our example this would be 172.16.4.1;172.16.4.2;172.16.4.3 > > Routers do not use subnet zero for anything unless instructed to do so and > > if this is the case, they will merely recognize it and route it. The > > broadcast address in a subnet does not see the entire network, it > broadcasts > > only to its entire sub-network. Referring to our example once more, this > > would be the address 172.16.4.7 and only the two host addresses on the > > subnet would hear a broadcast from it. > > > > Hope this clarifies things. > > > > > > > > >From: Jennifer Cribbs <[EMAIL PROTECTED]> > > >Reply-To: Jennifer Cribbs <[EMAIL PROTECTED]> > > >To: [EMAIL PROTECTED] > > >Subject: RE: Ip addressing question > > >Date: Thu, 25 Jan 2001 10:38:38 -0500 > > > > > >Subnet zero is the network address that the routers uses for routing to > the > > >network and the broadcast address sends a broadcast to the entire network > > >everytime it is used, which means it goes to all subnets. Therefore, > these > > >are not used as host addresses. They encompass the whole network. > Others > > >can > > >probably add to this. > > > > > >Jennifer Cribbs > > > > > > > > >= Original Message From "Fred Danson" <[EMAIL PROTECTED]> = > > > > Could anyone explain to me why Subnet zero and the last subnet are > > >not > > > >normally used?? I see why 2 host addresses are reserved in every subnet > > > >(network address and broadcast address), but I never understood why 2 > > > >networks are not used. What is the difference between these networks > and > > >the > > > >networks in between? > > > > > > > >Thanks in advance, > > > > > > > >Freddy > > > > > > > > > > > >_ > > > >Get your FREE download of MSN Explorer at http://explorer.msn.com > > > > > > > >_ > > > >FAQ, list archives, and subscription info: > > >http://www.groupstudy.com/list/cisco.html > > > >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > > > > > > >Have a Good Day!! > > >Jennifer Cribbs > > >[EMAIL PROTECTED] > > > > > >_ > > >FAQ, list archives, and subscription info: > > >http://www.groupstudy.com/list/cisco.html > > >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > > _ > > Get your FREE download of MSN Explorer at http://explorer.msn.com > > > > _ > > FAQ, list archives, and subscription info: > http://www.groupstudy.com/list/cisco.html > > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > > > _ > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Ip addressing question
But the third octet, would be 0100, which is contained within the subnet portion of the address, so how can this be subnet zero. I agree that 192.16.4.0 with 255.255.255.252 would be a subnet zero, because the fourth octet would be - 0011 and only the 6 MSB's count. If I'm being thick you're going to have to ram it down my neck. I would like to make my excuses now, it's getting late in U.K. Gareth ""Neil Schneider"" <[EMAIL PROTECTED]> wrote in message 94qe36$vpl$[EMAIL PROTECTED]">news:94qe36$vpl$[EMAIL PROTECTED]... > yes 172.16.4.0 thru 172.16.4.3 would be subnet zero. > > Neil Schneider > > > ""Gareth Hinton"" <[EMAIL PROTECTED]> wrote in message > 94qd3r$s2r$[EMAIL PROTECTED]">news:94qd3r$s2r$[EMAIL PROTECTED]... > > I've read it five times and still can't see a subnet zero in the example. > > 172.16.x.x Class B address with a 255.255.255.252 subnet mask. > > Wouldn't subnet zero be down at 172.16.0.0 with 172.16.0.4 being the first > > 'non-subnet zero' address. > > 172.16.4.0 wouldn't be subnet zero would it? > > > > Gareth > > > > ""Frank Wells"" <[EMAIL PROTECTED]> wrote in message > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > Hey Jen, > > > Your understanding of subnetting is a little off and your teaching is > thus > > > tainted. Here is a how subnetting and subnet zero work: > > > > > > Take a IP address for example:172. 16. 4. 0 > > > Add an easy subnet mask to play with: 255.255.255.252 > > > > > > What subnets to we get from this combo?... > > > First subnet= 172.16.4.4 > > > Second subnet= 172.16.4.8 > > > Third subnet= 172.16.4.12 > > > ... > > > Last subnet= 172.16.4.252 > > > > > > > > > Lets examine one of the subnets: 172.16.4.4 > > > The IP address space this subnet consumes is 172.16.4.4 through > 172.16.4.7 > > > The first and last IP addresses in the subnet range are the network > > address > > > and subnet broadcast address respectively, and neither the first or last > > > address can be used for host addressing, as is > > > well known. This leaves two remaining addresses available for hosts on > > that > > > subnet: > > > > > > 172.16.4.5 and 172.16.4.6 > > > > > > Subnet zero is that address space which is not taken up by the subnets. > > In > > > our example this would be 172.16.4.1;172.16.4.2;172.16.4.3 > > > Routers do not use subnet zero for anything unless instructed to do so > and > > > if this is the case, they will merely recognize it and route it. The > > > broadcast address in a subnet does not see the entire network, it > > broadcasts > > > only to its entire sub-network. Referring to our example once more, > this > > > would be the address 172.16.4.7 and only the two host addresses on the > > > subnet would hear a broadcast from it. > > > > > > Hope this clarifies things. > > > > > > > > > > > > >From: Jennifer Cribbs <[EMAIL PROTECTED]> > > > >Reply-To: Jennifer Cribbs <[EMAIL PROTECTED]> > > > >To: [EMAIL PROTECTED] > > > >Subject: RE: Ip addressing question > > > >Date: Thu, 25 Jan 2001 10:38:38 -0500 > > > > > > > >Subnet zero is the network address that the routers uses for routing to > > the > > > >network and the broadcast address sends a broadcast to the entire > network > > > >everytime it is used, which means it goes to all subnets. Therefore, > > these > > > >are not used as host addresses. They encompass the whole network. > > Others > > > >can > > > >probably add to this. > > > > > > > >Jennifer Cribbs > > > > > > > > > > > >= Original Message From "Fred Danson" <[EMAIL PROTECTED]> > = > > > > > Could anyone explain to me why Subnet zero and the last subnet > are > > > >not > > > > >normally used?? I see why 2 host addresses are reserved in every > subnet > > > > >(network address and broadcast address), but I never understood why 2 > > > > >networks are not used. What is the difference between these networks > > and > > > >the > > > > >networks in between? > > > > > > > > > >Thanks in advance, >
Re: Ip addressing question
Subnet-zero does not mean any of the IP address octets must have all zeros in them! It refers to that address space which falls outside the traditional subnets. >From: "Gareth Hinton" <[EMAIL PROTECTED]> >Reply-To: "Gareth Hinton" <[EMAIL PROTECTED]> >To: [EMAIL PROTECTED] >Subject: Re: Ip addressing question >Date: Thu, 25 Jan 2001 23:11:01 - > >But the third octet, would be 0100, which is contained within the >subnet >portion of the address, so how can this be subnet zero. >I agree that 192.16.4.0 with 255.255.255.252 would be a subnet zero, >because >the fourth octet would be - 0011 and only the 6 MSB's count. > >If I'm being thick you're going to have to ram it down my neck. >I would like to make my excuses now, it's getting late in U.K. > > >Gareth > > >""Neil Schneider"" <[EMAIL PROTECTED]> wrote in message >94qe36$vpl$[EMAIL PROTECTED]">news:94qe36$vpl$[EMAIL PROTECTED]... > > yes 172.16.4.0 thru 172.16.4.3 would be subnet zero. > > > > Neil Schneider > > > > > > ""Gareth Hinton"" <[EMAIL PROTECTED]> wrote in message > > 94qd3r$s2r$[EMAIL PROTECTED]">news:94qd3r$s2r$[EMAIL PROTECTED]... > > > I've read it five times and still can't see a subnet zero in the >example. > > > 172.16.x.x Class B address with a 255.255.255.252 subnet mask. > > > Wouldn't subnet zero be down at 172.16.0.0 with 172.16.0.4 being the >first > > > 'non-subnet zero' address. > > > 172.16.4.0 wouldn't be subnet zero would it? > > > > > > Gareth > > > > > > ""Frank Wells"" <[EMAIL PROTECTED]> wrote in message > > > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > > > Hey Jen, > > > > Your understanding of subnetting is a little off and your teaching >is > > thus > > > > tainted. Here is a how subnetting and subnet zero work: > > > > > > > > Take a IP address for example:172. 16. 4. 0 > > > > Add an easy subnet mask to play with: 255.255.255.252 > > > > > > > > What subnets to we get from this combo?... > > > > First subnet= 172.16.4.4 > > > > Second subnet= 172.16.4.8 > > > > Third subnet= 172.16.4.12 > > > > ... > > > > Last subnet= 172.16.4.252 > > > > > > > > > > > > Lets examine one of the subnets: 172.16.4.4 > > > > The IP address space this subnet consumes is 172.16.4.4 through > > 172.16.4.7 > > > > The first and last IP addresses in the subnet range are the network > > > address > > > > and subnet broadcast address respectively, and neither the first or >last > > > > address can be used for host addressing, as is > > > > well known. This leaves two remaining addresses available for hosts >on > > > that > > > > subnet: > > > > > > > > 172.16.4.5 and 172.16.4.6 > > > > > > > > Subnet zero is that address space which is not taken up by the >subnets. > > > In > > > > our example this would be 172.16.4.1;172.16.4.2;172.16.4.3 > > > > Routers do not use subnet zero for anything unless instructed to do >so > > and > > > > if this is the case, they will merely recognize it and route it. >The > > > > broadcast address in a subnet does not see the entire network, it > > > broadcasts > > > > only to its entire sub-network. Referring to our example once more, > > this > > > > would be the address 172.16.4.7 and only the two host addresses on >the > > > > subnet would hear a broadcast from it. > > > > > > > > Hope this clarifies things. > > > > > > > > > > > > > > > > >From: Jennifer Cribbs <[EMAIL PROTECTED]> > > > > >Reply-To: Jennifer Cribbs <[EMAIL PROTECTED]> > > > > >To: [EMAIL PROTECTED] > > > > >Subject: RE: Ip addressing question > > > > >Date: Thu, 25 Jan 2001 10:38:38 -0500 > > > > > > > > > >Subnet zero is the network address that the routers uses for >routing >to > > > the > > > > >network and the broadcast address sends a broadcast to the entire > > network > > > > >everytime it is used, which means it goes to all subnets. >Therefore, > > > these > > > > >are not
Re: Ip addressing question
This isn't quite correct. Gareth has it right. The zero subnet is relative to the classful boundary. Since 172.16.x.x is in the class B range, the zero subnet with a 30-bit mask -IS- 172.16.0.0 thru 172.16.0.3! >>> "Neil Schneider" <[EMAIL PROTECTED]> 01/25 2:42 PM >>> yes 172.16.4.0 thru 172.16.4.3 would be subnet zero. Neil Schneider ""Gareth Hinton"" <[EMAIL PROTECTED]> wrote in message 94qd3r$s2r$[EMAIL PROTECTED]">news:94qd3r$s2r$[EMAIL PROTECTED]... > I've read it five times and still can't see a subnet zero in the example. > 172.16.x.x Class B address with a 255.255.255.252 subnet mask. > Wouldn't subnet zero be down at 172.16.0.0 with 172.16.0.4 being the first > 'non-subnet zero' address. > 172.16.4.0 wouldn't be subnet zero would it? > > Gareth > > ""Frank Wells"" <[EMAIL PROTECTED]> wrote in message > [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > > Hey Jen, > > Your understanding of subnetting is a little off and your teaching is thus > > tainted. Here is a how subnetting and subnet zero work: > > > > Take a IP address for example:172. 16. 4. 0 > > Add an easy subnet mask to play with: 255.255.255.252 > > > > What subnets to we get from this combo?... > > First subnet= 172.16.4.4 > > Second subnet= 172.16.4.8 > > Third subnet= 172.16.4.12 > > ... > > Last subnet= 172.16.4.252 > > > > > > Lets examine one of the subnets: 172.16.4.4 > > The IP address space this subnet consumes is 172.16.4.4 through 172.16.4.7 > > The first and last IP addresses in the subnet range are the network > address > > and subnet broadcast address respectively, and neither the first or last > > address can be used for host addressing, as is > > well known. This leaves two remaining addresses available for hosts on > that > > subnet: > > > > 172.16.4.5 and 172.16.4.6 > > > > Subnet zero is that address space which is not taken up by the subnets. > In > > our example this would be 172.16.4.1;172.16.4.2;172.16.4.3 > > Routers do not use subnet zero for anything unless instructed to do so and > > if this is the case, they will merely recognize it and route it. The > > broadcast address in a subnet does not see the entire network, it > broadcasts > > only to its entire sub-network. Referring to our example once more, this > > would be the address 172.16.4.7 and only the two host addresses on the > > subnet would hear a broadcast from it. > > > > Hope this clarifies things. > > > > > > > > >From: Jennifer Cribbs <[EMAIL PROTECTED]> > > >Reply-To: Jennifer Cribbs <[EMAIL PROTECTED]> > > >To: [EMAIL PROTECTED] > > >Subject: RE: Ip addressing question > > >Date: Thu, 25 Jan 2001 10:38:38 -0500 > > > > > >Subnet zero is the network address that the routers uses for routing to > the > > >network and the broadcast address sends a broadcast to the entire network > > >everytime it is used, which means it goes to all subnets. Therefore, > these > > >are not used as host addresses. They encompass the whole network. > Others > > >can > > >probably add to this. > > > > > >Jennifer Cribbs > > > > > > > > >= Original Message From "Fred Danson" <[EMAIL PROTECTED]> = > > > > Could anyone explain to me why Subnet zero and the last subnet are > > >not > > > >normally used?? I see why 2 host addresses are reserved in every subnet > > > >(network address and broadcast address), but I never understood why 2 > > > >networks are not used. What is the difference between these networks > and > > >the > > > >networks in between? > > > > > > > >Thanks in advance, > > > > > > > >Freddy > > > > > > > > > > > >_ > > > >Get your FREE download of MSN Explorer at http://explorer.msn.com > > > > > > > >_ > > > >FAQ, list archives, and subscription info: > > >http://www.groupstudy.com/list/cisco.html > > > >Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > > > > > > > > >Have a Good Day!! > > >Jennifer Cribbs > > >[EMAIL PROTECTED] > > > > > >
Re: Ip addressing question
Ok, so subnet zero is not usable, I understand that. Is the last subnet usable even though it contains the 255 portion of the address? >What subnets to we get from this combo?... >First subnet= 172.16.4.4 >Second subnet= 172.16.4.8 >Third subnet= 172.16.4.12 >... >Last subnet= 172.16.4.252 _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Ip addressing question
Yes it is. The 172.16.4.255 ip address would be the 172.16.4.252 subnet broadcast address though. - Original Message - From: Jack <[EMAIL PROTECTED]> Newsgroups: groupstudy.cisco To: <[EMAIL PROTECTED]> Sent: Thursday, January 25, 2001 6:41 PM Subject: Re: Ip addressing question > Ok, so subnet zero is not usable, I understand that. > Is the last subnet usable even though it contains the 255 portion of the > address? > > >What subnets to we get from this combo?... > >First subnet= 172.16.4.4 > >Second subnet= 172.16.4.8 > >Third subnet= 172.16.4.12 > >... > >Last subnet= 172.16.4.252 > > > > _ > FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] > _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: Ip addressing question
RFC 950 was the original subnetting rule that did not allow the use of subnet zero. The new RFC 1812 does allow the use of subnet zero. This assumes that you are using a routing protocol that is aware of the difference between 131.107.0.0/16 and 131.107.0.0/17. _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
