Conceptual question: Reasoning behind private subnetting scheme?

Discussion in 'Cisco' started by John H., Mar 9, 2010.

  1. John H.

    John H. Guest

    We have a geographically dispersed WAN. All of the offices have
    192.168.n.0/24 local IP address. The point-to-point links between all
    of our routers are taken from the 192.168.65.0/24 network which has
    been subnetted into 64 two host subnets 192.168.65.0/30.

    Is there a reason the engineer that set up our network chose the
    192.168.65.0/24 network to subnet into the site-to-site links? Is
    this a standard or customary practice, or just his preference? Why
    not subnet 192.168.254.0 into the site-to-site networks?

    I’m just curious. I have looked all over and have not been able to
    find any documentation on customary use of private subnets in a
    situation like this. Is there a best practice defined somewhere?

    Thanks,
    John
    John H., Mar 9, 2010
    #1
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  2. "John H." <> writes:
    >We have a geographically dispersed WAN. All of the offices have
    >192.168.n.0/24 local IP address. The point-to-point links between all
    >of our routers are taken from the 192.168.65.0/24 network which has
    >been subnetted into 64 two host subnets 192.168.65.0/30.


    >Is there a reason the engineer that set up our network chose the
    >192.168.65.0/24 network to subnet into the site-to-site links? Is
    >this a standard or customary practice, or just his preference? Why
    >not subnet 192.168.254.0 into the site-to-site networks?


    >I=92m just curious. I have looked all over and have not been able to
    >find any documentation on customary use of private subnets in a
    >situation like this. Is there a best practice defined somewhere?


    They just picked it out of thin air.
    There is no best practice to choosing IP addressing like this, it just happens.
    Doug McIntyre, Mar 9, 2010
    #2
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  3. John H.

    bod43 Guest

    On 9 Mar, 14:58, Doug McIntyre <> wrote:
    > "John H." <> writes:
    > >We have a geographically dispersed WAN.  All of the offices have
    > >192.168.n.0/24 local IP address.  The point-to-point links between all
    > >of our routers are taken from the 192.168.65.0/24 network which has
    > >been subnetted into 64 two host subnets 192.168.65.0/30.
    > >Is there a reason the engineer that set up our network chose the
    > >192.168.65.0/24 network to subnet into the site-to-site links?  Is
    > >this a standard or customary practice, or just his preference?  Why
    > >not subnet 192.168.254.0 into the site-to-site networks?
    > >I=92m just curious.  I have looked all over and have not been able to
    > >find any documentation on customary use of private subnets in a
    > >situation like this.  Is there a best practice defined somewhere?

    >
    > They just picked it out of thin air.
    > There is no best practice to choosing IP addressing like this, it just happens.


    Well err, there is a reason for choosing particular
    addresses.

    If route summarisation is anticipated then it is
    a decent idea to chose addresses appropriately.

    For example:-

    192.168.0-63.x can be summarised into a single prefix.

    Similarly 128-255.

    So if 254 had been chosen then the opportunity to
    summarise 128-255 would have been lost.

    So perhaps the original designer was thinking ahead:)
    bod43, Mar 9, 2010
    #3
  4. John H.

    John H. Guest

    Thanks Bob43. Route summarization makes since. That was the concept
    I was not seeing.
    John H., Mar 10, 2010
    #4
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