Network Setup Question - TCP-IP

This is a discussion on Network Setup Question - TCP-IP ; Hi, I was asked as an exercise to divide up an internal network utilizing 10.0.0.0/8 into 16 different networks. Can someone please review the few that I've listed below for accuracy? Also, would I be correct in that there are ...

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  1. Network Setup Question

    Hi,

    I was asked as an exercise to divide up an internal network utilizing
    10.0.0.0/8 into 16 different networks. Can someone please review the
    few that I've listed below for accuracy? Also, would I be correct in
    that there are 24 host bits in each network?

    Thanks,
    James


    #1
    Subnet Mask Subnet Size
    172.16.0.0 255.255.240.0 4094

    Host Range Broadcast
    172.16.0.1 to 172.16.15.254 172.16.15.255

    #2
    Subnet Mask Subnet Size
    172.16.16.0 255.255.240.0 4094

    Host Range Broadcast
    172.16.16.1 to 172.16.31.254 172.16.31.255

    #3
    Subnet Mask Subnet Size
    172.16.32.0 255.255.240.0 4094

    Host Range Broadcast
    172.16.32.1 to 172.16.47.254 172.16.47.255


  2. Re: Network Setup Question

    In article <1149650529.505831.9220@g10g2000cwb.googlegroups.co m>,
    wrote:
    >I was asked as an exercise to divide up an internal network utilizing
    >10.0.0.0/8 into 16 different networks.


    Was it specified as 10.0.0.0/8 or as 10.0.0.0 with a netmask of 255.0.0.0 ?
    If it was specified in terms of the netmask instead of /8 then it
    was a trick question; google for "ip subnet-zero" to see why.

    >Can someone please review the
    >few that I've listed below for accuracy?


    >#1
    >Subnet Mask Subnet Size
    >172.16.0.0 255.255.240.0 4094


    Potentially not valid; cf. the subnet-zero reference.


    >Also, would I be correct in
    >that there are 24 host bits in each network?


    No. Count the number of leading binary 1's in 255.255.240.0 .

  3. Re: Network Setup Question

    In article <1149650529.505831.9220@g10g2000cwb.googlegroups.co m>,
    v8killah03@yahoo.com wrote:

    > Hi,
    >
    > I was asked as an exercise to divide up an internal network utilizing
    > 10.0.0.0/8 into 16 different networks. Can someone please review the
    > few that I've listed below for accuracy? Also, would I be correct in
    > that there are 24 host bits in each network?


    If you were asked to break up 10.0.0.0/8, why do all the networks in
    your response start with 172.16? They should be 10.x.x.x.

    >
    > Thanks,
    > James
    >
    >
    > #1
    > Subnet Mask Subnet Size
    > 172.16.0.0 255.255.240.0 4094
    >
    > Host Range Broadcast
    > 172.16.0.1 to 172.16.15.254 172.16.15.255
    >
    > #2
    > Subnet Mask Subnet Size
    > 172.16.16.0 255.255.240.0 4094
    >
    > Host Range Broadcast
    > 172.16.16.1 to 172.16.31.254 172.16.31.255
    >
    > #3
    > Subnet Mask Subnet Size
    > 172.16.32.0 255.255.240.0 4094
    >
    > Host Range Broadcast
    > 172.16.32.1 to 172.16.47.254 172.16.47.255


    --
    Barry Margolin, barmar@alum.mit.edu
    Arlington, MA
    *** PLEASE post questions in newsgroups, not directly to me ***
    *** PLEASE don't copy me on replies, I'll read them in the group ***

  4. Re: Network Setup Question

    I was going off an example that I found. So, should I change all
    values of 172.16... to 10.16...., effectively replacing all values 172
    to 10?

    Also, regarding a previous reply to my message, it was stated as
    10.0.0.0/8.

    Thanks a lot!!

    James


    Barry Margolin wrote:
    > In article <1149650529.505831.9220@g10g2000cwb.googlegroups.co m>,
    > v8killah03@yahoo.com wrote:
    >
    > > Hi,
    > >
    > > I was asked as an exercise to divide up an internal network utilizing
    > > 10.0.0.0/8 into 16 different networks. Can someone please review the
    > > few that I've listed below for accuracy? Also, would I be correct in
    > > that there are 24 host bits in each network?

    >
    > If you were asked to break up 10.0.0.0/8, why do all the networks in
    > your response start with 172.16? They should be 10.x.x.x.
    >
    > >
    > > Thanks,
    > > James
    > >
    > >
    > > #1
    > > Subnet Mask Subnet Size
    > > 172.16.0.0 255.255.240.0 4094
    > >
    > > Host Range Broadcast
    > > 172.16.0.1 to 172.16.15.254 172.16.15.255
    > >
    > > #2
    > > Subnet Mask Subnet Size
    > > 172.16.16.0 255.255.240.0 4094
    > >
    > > Host Range Broadcast
    > > 172.16.16.1 to 172.16.31.254 172.16.31.255
    > >
    > > #3
    > > Subnet Mask Subnet Size
    > > 172.16.32.0 255.255.240.0 4094
    > >
    > > Host Range Broadcast
    > > 172.16.32.1 to 172.16.47.254 172.16.47.255

    >
    > --
    > Barry Margolin, barmar@alum.mit.edu
    > Arlington, MA
    > *** PLEASE post questions in newsgroups, not directly to me ***
    > *** PLEASE don't copy me on replies, I'll read them in the group ***



  5. Re: Network Setup Question

    In article <1149684598.478740.142770@y43g2000cwc.googlegroups. com>,
    v8killah03@yahoo.com wrote:

    > I was going off an example that I found. So, should I change all
    > values of 172.16... to 10.16...., effectively replacing all values 172
    > to 10?


    Yes. Otherwise you're not dividing up the same network you were told to
    divide up.

    But this also changed the rest of the answer, like the appropriate
    subnet mask to use. Your answer was correct if you were asked to divide
    up a /16, not a /8.

    >
    > Also, regarding a previous reply to my message, it was stated as
    > 10.0.0.0/8.
    >
    > Thanks a lot!!
    >
    > James
    >
    >
    > Barry Margolin wrote:
    > > In article <1149650529.505831.9220@g10g2000cwb.googlegroups.co m>,
    > > v8killah03@yahoo.com wrote:
    > >
    > > > Hi,
    > > >
    > > > I was asked as an exercise to divide up an internal network utilizing
    > > > 10.0.0.0/8 into 16 different networks. Can someone please review the
    > > > few that I've listed below for accuracy? Also, would I be correct in
    > > > that there are 24 host bits in each network?

    > >
    > > If you were asked to break up 10.0.0.0/8, why do all the networks in
    > > your response start with 172.16? They should be 10.x.x.x.
    > >
    > > >
    > > > Thanks,
    > > > James
    > > >
    > > >
    > > > #1
    > > > Subnet Mask Subnet Size
    > > > 172.16.0.0 255.255.240.0 4094
    > > >
    > > > Host Range Broadcast
    > > > 172.16.0.1 to 172.16.15.254 172.16.15.255
    > > >
    > > > #2
    > > > Subnet Mask Subnet Size
    > > > 172.16.16.0 255.255.240.0 4094
    > > >
    > > > Host Range Broadcast
    > > > 172.16.16.1 to 172.16.31.254 172.16.31.255
    > > >
    > > > #3
    > > > Subnet Mask Subnet Size
    > > > 172.16.32.0 255.255.240.0 4094
    > > >
    > > > Host Range Broadcast
    > > > 172.16.32.1 to 172.16.47.254 172.16.47.255

    > >
    > > --
    > > Barry Margolin, barmar@alum.mit.edu
    > > Arlington, MA
    > > *** PLEASE post questions in newsgroups, not directly to me ***
    > > *** PLEASE don't copy me on replies, I'll read them in the group ***


    --
    Barry Margolin, barmar@alum.mit.edu
    Arlington, MA
    *** PLEASE post questions in newsgroups, not directly to me ***
    *** PLEASE don't copy me on replies, I'll read them in the group ***

  6. Re: Network Setup Question

    In article ,
    Barry Margolin wrote:

    >But this also changed the rest of the answer, like the appropriate
    >subnet mask to use. Your answer was correct if you were asked to divide
    >up a /16, not a /8.


    The question as stated did not require that the 16 subnetworks
    together cover the original network; nor that the 16 subnetworks were
    each the same size. For example, the question as stated could
    have been solved with one each of a /9 through /23 and two /24.


  7. Re: Network Setup Question

    I think I get it now. So, something like this? Thanks again for the
    help btw.

    #1
    Subnet Mask Subnet Size
    10.8.0.0 255.255.240.0 4094


    Host Range Broadcast
    10.16.0.1 to 10.8.7.254 10.8.7.255


    #2
    Subnet Mask Subnet Size
    10.8.8.0 255.255.240.0 4094


    Host Range Broadcast
    10.8.8.1 to 10.8.15.254 10.8.15.255


    #3
    Subnet Mask Subnet Size
    10.8.16.0 255.255.240.0 4094


    Host Range Broadcast
    10.8.16.1 to 10.8.23.254 10.8.23.255

    Barry Margolin wrote:
    > In article <1149684598.478740.142770@y43g2000cwc.googlegroups. com>,
    > v8killah03@yahoo.com wrote:
    >
    > > I was going off an example that I found. So, should I change all
    > > values of 172.16... to 10.16...., effectively replacing all values 172
    > > to 10?

    >
    > Yes. Otherwise you're not dividing up the same network you were told to
    > divide up.
    >
    > But this also changed the rest of the answer, like the appropriate
    > subnet mask to use. Your answer was correct if you were asked to divide
    > up a /16, not a /8.
    >
    > >
    > > Also, regarding a previous reply to my message, it was stated as
    > > 10.0.0.0/8.
    > >
    > > Thanks a lot!!
    > >
    > > James
    > >
    > >
    > > Barry Margolin wrote:
    > > > In article <1149650529.505831.9220@g10g2000cwb.googlegroups.co m>,
    > > > v8killah03@yahoo.com wrote:
    > > >
    > > > > Hi,
    > > > >
    > > > > I was asked as an exercise to divide up an internal network utilizing
    > > > > 10.0.0.0/8 into 16 different networks. Can someone please review the
    > > > > few that I've listed below for accuracy? Also, would I be correct in
    > > > > that there are 24 host bits in each network?
    > > >
    > > > If you were asked to break up 10.0.0.0/8, why do all the networks in
    > > > your response start with 172.16? They should be 10.x.x.x.
    > > >
    > > > >
    > > > > Thanks,
    > > > > James
    > > > >
    > > > >
    > > > > #1
    > > > > Subnet Mask Subnet Size
    > > > > 172.16.0.0 255.255.240.0 4094
    > > > >
    > > > > Host Range Broadcast
    > > > > 172.16.0.1 to 172.16.15.254 172.16.15.255
    > > > >
    > > > > #2
    > > > > Subnet Mask Subnet Size
    > > > > 172.16.16.0 255.255.240.0 4094
    > > > >
    > > > > Host Range Broadcast
    > > > > 172.16.16.1 to 172.16.31.254 172.16.31.255
    > > > >
    > > > > #3
    > > > > Subnet Mask Subnet Size
    > > > > 172.16.32.0 255.255.240.0 4094
    > > > >
    > > > > Host Range Broadcast
    > > > > 172.16.32.1 to 172.16.47.254 172.16.47.255
    > > >
    > > > --
    > > > Barry Margolin, barmar@alum.mit.edu
    > > > Arlington, MA
    > > > *** PLEASE post questions in newsgroups, not directly to me ***
    > > > *** PLEASE don't copy me on replies, I'll read them in the group ***

    >
    > --
    > Barry Margolin, barmar@alum.mit.edu
    > Arlington, MA
    > *** PLEASE post questions in newsgroups, not directly to me ***
    > *** PLEASE don't copy me on replies, I'll read them in the group ***



  8. Re: Network Setup Question

    Think binary:
    Mask:
    11111111.00000000.00000000.00000000
    IPs
    00001010.xxxxxxxx.00000000.00000000

    The x's is what you have to divide, and you want to make that
    difference as large as you want, then you start moving your most
    significant bits until you fix your problem:

    xxxxxxxx:
    0000 0000 = 0
    0001 0000 = 16
    0010 0000 = 32
    0011 0000 = 48
    0100 0000 = 64
    0101 0000 = ...
    0110 0000
    0111 0000
    1000 0000
    1001 0000
    1010 0000
    1011 0000
    1100 0000
    1101 0000
    1110 0000
    1111 0000


    v8killah03@yahoo.com wrote:
    > I think I get it now. So, something like this? Thanks again for the
    > help btw.
    >
    > #1
    > Subnet Mask Subnet Size
    > 10.8.0.0 255.255.240.0 4094
    >
    >
    > Host Range Broadcast
    > 10.16.0.1 to 10.8.7.254 10.8.7.255
    >
    >
    > #2
    > Subnet Mask Subnet Size
    > 10.8.8.0 255.255.240.0 4094
    >
    >
    > Host Range Broadcast
    > 10.8.8.1 to 10.8.15.254 10.8.15.255
    >
    >
    > #3
    > Subnet Mask Subnet Size
    > 10.8.16.0 255.255.240.0 4094
    >
    >
    > Host Range Broadcast
    > 10.8.16.1 to 10.8.23.254 10.8.23.255
    >
    > Barry Margolin wrote:
    > > In article <1149684598.478740.142770@y43g2000cwc.googlegroups. com>,
    > > v8killah03@yahoo.com wrote:
    > >
    > > > I was going off an example that I found. So, should I change all
    > > > values of 172.16... to 10.16...., effectively replacing all values 172
    > > > to 10?

    > >
    > > Yes. Otherwise you're not dividing up the same network you were told to
    > > divide up.
    > >
    > > But this also changed the rest of the answer, like the appropriate
    > > subnet mask to use. Your answer was correct if you were asked to divide
    > > up a /16, not a /8.
    > >
    > > >
    > > > Also, regarding a previous reply to my message, it was stated as
    > > > 10.0.0.0/8.
    > > >
    > > > Thanks a lot!!
    > > >
    > > > James
    > > >
    > > >
    > > > Barry Margolin wrote:
    > > > > In article <1149650529.505831.9220@g10g2000cwb.googlegroups.co m>,
    > > > > v8killah03@yahoo.com wrote:
    > > > >
    > > > > > Hi,
    > > > > >
    > > > > > I was asked as an exercise to divide up an internal network utilizing
    > > > > > 10.0.0.0/8 into 16 different networks. Can someone please review the
    > > > > > few that I've listed below for accuracy? Also, would I be correct in
    > > > > > that there are 24 host bits in each network?
    > > > >
    > > > > If you were asked to break up 10.0.0.0/8, why do all the networks in
    > > > > your response start with 172.16? They should be 10.x.x.x.
    > > > >
    > > > > >
    > > > > > Thanks,
    > > > > > James
    > > > > >
    > > > > >
    > > > > > #1
    > > > > > Subnet Mask Subnet Size
    > > > > > 172.16.0.0 255.255.240.0 4094
    > > > > >
    > > > > > Host Range Broadcast
    > > > > > 172.16.0.1 to 172.16.15.254 172.16.15.255
    > > > > >
    > > > > > #2
    > > > > > Subnet Mask Subnet Size
    > > > > > 172.16.16.0 255.255.240.0 4094
    > > > > >
    > > > > > Host Range Broadcast
    > > > > > 172.16.16.1 to 172.16.31.254 172.16.31.255
    > > > > >
    > > > > > #3
    > > > > > Subnet Mask Subnet Size
    > > > > > 172.16.32.0 255.255.240.0 4094
    > > > > >
    > > > > > Host Range Broadcast
    > > > > > 172.16.32.1 to 172.16.47.254 172.16.47.255
    > > > >
    > > > > --
    > > > > Barry Margolin, barmar@alum.mit.edu
    > > > > Arlington, MA
    > > > > *** PLEASE post questions in newsgroups, not directly to me ***
    > > > > *** PLEASE don't copy me on replies, I'll read them in the group ***

    > >
    > > --
    > > Barry Margolin, barmar@alum.mit.edu
    > > Arlington, MA
    > > *** PLEASE post questions in newsgroups, not directly to me ***
    > > *** PLEASE don't copy me on replies, I'll read them in the group ***



  9. Re: Network Setup Question

    Hmmm, so then 3 networks on 10.0.0.0/8 would be:

    10.8.0.0
    10.16.0.0
    10.24.0.0

    Seems way to simple, which is why I think I'm doing something wrong.

    Regarding the mask, the first one you listed is 128.0.0.0, is that
    correct?

    Please forgive my ignorance.

    Thanks,
    James


  10. Re: Network Setup Question

    How does this look?

    Network # IP Range
    1 10.1.0.0 10.1.0.1 - 10.1.255.254
    2 10.2.0.0 10.2.0.1 - 10.2.255.254
    3 10.3.0.0 10.3.0.1 - 10.3.255.254

    Broadcast
    10.1.255.255
    10.2.255.255
    10.3.255.255


    65534 hosts per network


    Thanks,
    James


  11. Re: Network Setup Question

    In article <1149694624.144984.89630@c74g2000cwc.googlegroups.c om>,
    wrote:
    >Hmmm, so then 3 networks on 10.0.0.0/8 would be:


    >10.8.0.0
    >10.16.0.0
    >10.24.0.0


    >Seems way to simple, which is why I think I'm doing something wrong.


    Those are three possible subnets of 10/8 -- though you haven't
    been clear as to whether the netmask you are using is 255.255.0.0
    or 255.252.0.0 .

    If you want to divide 10/8 into three subnets of maximum size, then
    one possible division would be 10.0/9, 10.128/10, 10.192/10
    for which the respective netmasks would be 255.128.0.0, 255.192.0.0,
    and 255.192.0.0, and the respective IP ranges would be
    10.0.0.0 - 10.127.255.255, 10.128.0.0 - 10.191.255.255, and
    10.192.0.0 - 10.255.255.255 .

    If all the subnets must be the same size, then you could "waste" one
    of the subnets and use any three of

    10.0/10, 10.64/10, 10.128/10, 10.192/10 . The netmask for each
    of these would be 255.192.0.0

  12. Re: Network Setup Question

    I've been playing around with this for a little longer now and came up
    with these. Of the 16 networks that I want out of 10.0.0.0/8, I got
    these 4 using the calculator at
    http://networking.ringofsaturn.com/IP/subnet.php. Can anyone verify
    the correctness?:

    Network Hosts Broadcast Address
    10.0.0.0 10.0.0.1 to 10.15.255.254 10.15.255.255
    10.16.0.0 10.16.0.1 to 10.31.255.254 10.31.255.255
    10.32.0.0 10.32.0.1 to 10.47.255.254 10.47.255.255
    10.48.0.0 10.48.0.1 to 10.63.255.254 10.63.255.255

    Thanks again,
    James


  13. Re: Network Setup Question

    In article ,
    roberson@hushmail.com (Walter Roberson) wrote:

    > In article ,
    > Barry Margolin wrote:
    >
    > >But this also changed the rest of the answer, like the appropriate
    > >subnet mask to use. Your answer was correct if you were asked to divide
    > >up a /16, not a /8.

    >
    > The question as stated did not require that the 16 subnetworks
    > together cover the original network; nor that the 16 subnetworks were
    > each the same size. For example, the question as stated could
    > have been solved with one each of a /9 through /23 and two /24.


    True, but unless otherwise specified it's natural to subnet equally and
    fully.

    --
    Barry Margolin, barmar@alum.mit.edu
    Arlington, MA
    *** PLEASE post questions in newsgroups, not directly to me ***
    *** PLEASE don't copy me on replies, I'll read them in the group ***

  14. Re: Network Setup Question


    wrote in message
    news:1149650529.505831.9220@g10g2000cwb.googlegrou ps.com...
    > Hi,
    >
    > I was asked as an exercise to divide up an internal network utilizing
    > 10.0.0.0/8 into 16 different networks.


    To create 16 usable subnets you have to bowrrow 5 bits from the host
    address.
    Now play around with 10.0.0.0/13

    new guy



  15. Re: Network Setup Question

    In article <5eWhg.255845$7a.242054@pd7tw1no>,
    new guy guy@now.anonymous> wrote:

    > wrote in message
    >news:1149650529.505831.9220@g10g2000cwb.googlegrou ps.com...


    >> I was asked as an exercise to divide up an internal network utilizing
    >> 10.0.0.0/8 into 16 different networks.


    >To create 16 usable subnets you have to bowrrow 5 bits from the host
    >address.
    >Now play around with 10.0.0.0/13


    I notice you say "16 usable subnets". It appears that you are taking
    into account the reservation of the first and last subnet. However,
    that reservation was eliminated for CIDR, which is commonly
    denoted with VLSM (Variable Length Subnet Mask). When you are using
    CIDR, you can produce N usable subnets with ceiling(log(N)/log(2))
    bits -- i.e., 4 bits in the case of 16 subnets

    One of the first things I asked was whether the original question
    had specified 10.0.0.0/8 (i.e., VLSM), or had specified
    10.0.0.0 255.0.0.0 (i.e., classical subnetting.) The answer from
    the original poster was the VLSM form, so we need not take into
    account the reserved subnets.

  16. Re: Network Setup Question


    "Walter Roberson" wrote in message
    news:ayWhg.256553$P01.208904@pd7tw3no...
    > In article <5eWhg.255845$7a.242054@pd7tw1no>,
    > new guy guy@now.anonymous> wrote:
    >
    >> wrote in message
    >>news:1149650529.505831.9220@g10g2000cwb.googlegrou ps.com...

    >
    >>> I was asked as an exercise to divide up an internal network utilizing
    >>> 10.0.0.0/8 into 16 different networks.

    >
    >>To create 16 usable subnets you have to bowrrow 5 bits from the host
    >>address.
    >>Now play around with 10.0.0.0/13

    >
    > I notice you say "16 usable subnets". It appears that you are taking
    > into account the reservation of the first and last subnet. However,
    > that reservation was eliminated for CIDR, which is commonly
    > denoted with VLSM (Variable Length Subnet Mask). When you are using
    > CIDR, you can produce N usable subnets with ceiling(log(N)/log(2))
    > bits -- i.e., 4 bits in the case of 16 subnets


    > One of the first things I asked was whether the original question
    > had specified 10.0.0.0/8 (i.e., VLSM), or had specified
    > 10.0.0.0 255.0.0.0 (i.e., classical subnetting.) The answer from
    > the original poster was the VLSM form, so we need not take into
    > account the reserved subnets.


    10.0.0.0 is a classful network IP address. /8 and 255.0.0.0 are two ways of
    expressing exactly the same mask!!!
    Nowadays, slash format is more common .....

    new guy



  17. Re: Network Setup Question

    In article ,
    new guy guy@now.anonymous> wrote:
    >"Walter Roberson" wrote in message
    >news:ayWhg.256553$P01.208904@pd7tw3no...
    > ...
    >> One of the first things I asked was whether the original question
    >> had specified 10.0.0.0/8 (i.e., VLSM), or had specified
    >> 10.0.0.0 255.0.0.0 (i.e., classical subnetting.) The answer from
    >> the original poster was the VLSM form, so we need not take into
    >> account the reserved subnets.

    >
    >10.0.0.0 is a classful network IP address. /8 and 255.0.0.0 are two ways of
    >expressing exactly the same mask!!!
    >Nowadays, slash format is more common .....


    Don't be mislead by paying attention only to the mask. Yes the bit
    pattern may be identical but 'classful' brings in a lot more baggage
    than just the netmask.

    --
    -- Rod --
    rodd(at)polylogics(dot)com

  18. Re: Network Setup Question


    "Rod Dorman" wrote in message
    news:e6f681$5rc$1@reader2.panix.com...
    > In article ,
    > new guy guy@now.anonymous> wrote:
    >>"Walter Roberson" wrote in message
    >>news:ayWhg.256553$P01.208904@pd7tw3no...
    >> ...
    >>> One of the first things I asked was whether the original question
    >>> had specified 10.0.0.0/8 (i.e., VLSM), or had specified
    >>> 10.0.0.0 255.0.0.0 (i.e., classical subnetting.) The answer from
    >>> the original poster was the VLSM form, so we need not take into
    >>> account the reserved subnets.

    >>
    >>10.0.0.0 is a classful network IP address. /8 and 255.0.0.0 are two ways
    >>of
    >>expressing exactly the same mask!!!
    >>Nowadays, slash format is more common .....

    >
    > Don't be mislead by paying attention only to the mask. Yes the bit
    > pattern may be identical but 'classful' brings in a lot more baggage
    > than just the netmask.



    What kind of baggage are you talking about?

    new guy



  19. Re: Network Setup Question

    In article ,
    new guy guy@now.anonymous> wrote:
    >
    >"Rod Dorman" wrote in message
    >news:e6f681$5rc$1@reader2.panix.com...
    >> In article ,
    >> new guy guy@now.anonymous> wrote:
    >>> ...
    >>>10.0.0.0 is a classful network IP address. /8 and 255.0.0.0 are two
    >>>ways of expressing exactly the same mask!!! Nowadays, slash format
    >>>is more common .....

    >>
    >> Don't be mislead by paying attention only to the mask. Yes the bit
    >> pattern may be identical but 'classful' brings in a lot more baggage
    >> than just the netmask.

    >
    >What kind of baggage are you talking about?


    CIDR notation (what you called slash format) tells you only one thing,
    the number of significant bits used to identify a network.

    Classful determines the netmask from the first few bits of the IP
    address, early versions of BGP never needed to transmit a netmask
    since they 'knew' what it had to be.

    You also had issues when subnetting with avoiding the all-zeros and
    all-ones subnets. Cisco's IOS added an ip subnet-zero command to be
    able to control its behaviour.

    Stating something is class A/B/C can be confusing when its not clear
    if you are simply specifying the netmask vs. depending upon classful
    behaviour so in general if all you want to convey is the netmask CIDR
    is preferred.

    --
    -- Rod --
    rodd(at)polylogics(dot)com

  20. Re: Network Setup Question


    "Rod Dorman" wrote in message
    news:e6mv5a$etb$1@reader2.panix.com...
    > In article ,
    > new guy guy@now.anonymous> wrote:
    >>
    >>"Rod Dorman" wrote in message
    >>news:e6f681$5rc$1@reader2.panix.com...
    >>> In article ,
    >>> new guy guy@now.anonymous> wrote:
    >>>> ...
    >>>>10.0.0.0 is a classful network IP address. /8 and 255.0.0.0 are two
    >>>>ways of expressing exactly the same mask!!! Nowadays, slash format
    >>>>is more common .....
    >>>
    >>> Don't be mislead by paying attention only to the mask. Yes the bit
    >>> pattern may be identical but 'classful' brings in a lot more baggage
    >>> than just the netmask.

    >>
    >>What kind of baggage are you talking about?

    >
    > CIDR notation (what you called slash format) tells you only one thing,
    > the number of significant bits used to identify a network.



    No, that's not what the slash format tells me. i.e. 10.0.0.0/18 tells me
    that the second octet and 2 bits from the third octet were borrowed to
    create subnets.

    >
    > Classful determines the netmask from the first few bits of the IP
    > address, early versions of BGP never needed to transmit a netmask
    > since they 'knew' what it had to be.
    >
    > You also had issues when subnetting with avoiding the all-zeros and
    > all-ones subnets. Cisco's IOS added an ip subnet-zero command to be
    > able to control its behaviour.
    >
    > Stating something is class A/B/C can be confusing when its not clear
    > if you are simply specifying the netmask vs. depending upon classful
    > behaviour so in general if all you want to convey is the netmask CIDR
    > is preferred.


    You are just complicating things unneccessarily ....

    new guy



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