Subnetting

Discussion in 'Cisco' started by AC, Jul 18, 2003.

  1. AC

    AC Guest

    Set up the scenario a little here:

    We have a /23 network coming in through a Cisco router. At the moment, our
    Linux box is using proxy arp and has the network divided into two pieces. I
    want to elimate proxy arp and use the Linux box as a proper router.
    Basically I want to take our /23 and cut it into two /24s.

    I'm pretty sure I can do the configuration on the Linux box, but the Cisco
    box has me a little confused. I think it might be as simple as the IOS
    command:

    ip route y.y.y.y 255.255.255.0 x.x.x.21

    (where y is the upper /24 and x is the lower /24).

    Is this right, or am I missing something?

    --
    Aaron Clausen

     
    AC, Jul 18, 2003
    #1
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  2. In article <>,
    AC <> wrote:
    >Set up the scenario a little here:
    >
    >We have a /23 network coming in through a Cisco router. At the moment, our
    >Linux box is using proxy arp and has the network divided into two pieces. I
    >want to elimate proxy arp and use the Linux box as a proper router.
    >Basically I want to take our /23 and cut it into two /24s.
    >
    >I'm pretty sure I can do the configuration on the Linux box, but the Cisco
    >box has me a little confused. I think it might be as simple as the IOS
    >command:
    >
    >ip route y.y.y.y 255.255.255.0 x.x.x.21
    >
    >(where y is the upper /24 and x is the lower /24).
    >
    >Is this right, or am I missing something?


    You're right.

    --
    Barry Margolin,
    Level(3), Woburn, MA
    *** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
    Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.
     
    Barry Margolin, Jul 18, 2003
    #2
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  3. AC

    AC Guest

    On Fri, 18 Jul 2003 17:05:04 GMT,
    Barry Margolin <> wrote:
    > In article <>,
    > AC <> wrote:
    >>Set up the scenario a little here:
    >>
    >>We have a /23 network coming in through a Cisco router. At the moment, our
    >>Linux box is using proxy arp and has the network divided into two pieces. I
    >>want to elimate proxy arp and use the Linux box as a proper router.
    >>Basically I want to take our /23 and cut it into two /24s.
    >>
    >>I'm pretty sure I can do the configuration on the Linux box, but the Cisco
    >>box has me a little confused. I think it might be as simple as the IOS
    >>command:
    >>
    >>ip route y.y.y.y 255.255.255.0 x.x.x.21
    >>
    >>(where y is the upper /24 and x is the lower /24).
    >>
    >>Is this right, or am I missing something?

    >
    > You're right.


    I'm glad I'm right about something. Let's try a more tangible example.

    We've got a /23:

    10.101.104.0/23

    Ethernet1 on the cisco unit has the following configuration:

    interface Ethernet1
    ip address 10.101.104.0 255.255.254.0
    no ip directed-broadcast

    To forward the upper /24 to the Linux router, the entry is:

    ip route 10.101.105.0 255.255.255.0 10.101.104.2

    (Where 10.101.104.2 is the Linux router's address on the lower /24)

    It's that simple from the Cisco box?

    --
    Aaron Clausen

     
    AC, Jul 18, 2003
    #3
  4. In article <>,
    AC <> wrote:
    >I'm glad I'm right about something. Let's try a more tangible example.
    >
    >We've got a /23:
    >
    >10.101.104.0/23
    >
    >Ethernet1 on the cisco unit has the following configuration:
    >
    >interface Ethernet1
    > ip address 10.101.104.0 255.255.254.0
    > no ip directed-broadcast
    >
    >To forward the upper /24 to the Linux router, the entry is:
    >
    >ip route 10.101.105.0 255.255.255.0 10.101.104.2
    >
    >(Where 10.101.104.2 is the Linux router's address on the lower /24)
    >
    >It's that simple from the Cisco box?


    Yes. You would also normally change the subnet mask in the "ip address"
    statement to 255.255.255.0.

    --
    Barry Margolin,
    Level(3), Woburn, MA
    *** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
    Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.
     
    Barry Margolin, Jul 18, 2003
    #4
  5. AC

    AC Guest

    On Fri, 18 Jul 2003 20:14:16 GMT,
    Barry Margolin <> wrote:
    > In article <>,
    > AC <> wrote:
    >>I'm glad I'm right about something. Let's try a more tangible example.
    >>
    >>We've got a /23:
    >>
    >>10.101.104.0/23
    >>
    >>Ethernet1 on the cisco unit has the following configuration:
    >>
    >>interface Ethernet1
    >> ip address 10.101.104.0 255.255.254.0
    >> no ip directed-broadcast
    >>
    >>To forward the upper /24 to the Linux router, the entry is:
    >>
    >>ip route 10.101.105.0 255.255.255.0 10.101.104.2
    >>
    >>(Where 10.101.104.2 is the Linux router's address on the lower /24)
    >>
    >>It's that simple from the Cisco box?

    >
    > Yes. You would also normally change the subnet mask in the "ip address"
    > statement to 255.255.255.0.


    So the Ethernet1 config would like this?

    interface Ethernet1
    ip address 10.101.104.0 255.255.255.0
    no ip directed-broadcast

    --
    Aaron Clausen

     
    AC, Jul 18, 2003
    #5
  6. In article <>,
    AC <> wrote:
    >On Fri, 18 Jul 2003 20:14:16 GMT,
    >Barry Margolin <> wrote:
    >> Yes. You would also normally change the subnet mask in the "ip address"
    >> statement to 255.255.255.0.

    >
    >So the Ethernet1 config would like this?
    >
    >interface Ethernet1
    > ip address 10.101.104.0 255.255.255.0
    > no ip directed-broadcast


    Actually, the address needs to be in the range 10.101.104.1 through
    10.101.104.254. .0 is the network address and .255 is the broadcast
    address.

    --
    Barry Margolin,
    Level(3), Woburn, MA
    *** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
    Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.
     
    Barry Margolin, Jul 18, 2003
    #6
  7. AC

    AC Guest

    On Fri, 18 Jul 2003 21:39:36 GMT,
    Barry Margolin <> wrote:
    > In article <>,
    > AC <> wrote:
    >>On Fri, 18 Jul 2003 20:14:16 GMT,
    >>Barry Margolin <> wrote:
    >>> Yes. You would also normally change the subnet mask in the "ip address"
    >>> statement to 255.255.255.0.

    >>
    >>So the Ethernet1 config would like this?
    >>
    >>interface Ethernet1
    >> ip address 10.101.104.0 255.255.255.0
    >> no ip directed-broadcast

    >
    > Actually, the address needs to be in the range 10.101.104.1 through
    > 10.101.104.254. .0 is the network address and .255 is the broadcast
    > address.


    Okay. Can you give me an example of how the Interface commands should look?
    Sorry to be a pain, but I feel like I'm missing something here.

    --
    Aaron Clausen

     
    AC, Jul 21, 2003
    #7
  8. In article <>,
    AC <> wrote:
    >On Fri, 18 Jul 2003 21:39:36 GMT,
    >Barry Margolin <> wrote:
    >> In article <>,
    >> AC <> wrote:
    >>>On Fri, 18 Jul 2003 20:14:16 GMT,
    >>>Barry Margolin <> wrote:
    >>>> Yes. You would also normally change the subnet mask in the "ip address"
    >>>> statement to 255.255.255.0.
    >>>
    >>>So the Ethernet1 config would like this?
    >>>
    >>>interface Ethernet1
    >>> ip address 10.101.104.0 255.255.255.0
    >>> no ip directed-broadcast

    >>
    >> Actually, the address needs to be in the range 10.101.104.1 through
    >> 10.101.104.254. .0 is the network address and .255 is the broadcast
    >> address.

    >
    >Okay. Can you give me an example of how the Interface commands should look?
    >Sorry to be a pain, but I feel like I'm missing something here.


    interface Ethernet1
    ip address 10.101.104.1 255.255.255.0

    --
    Barry Margolin,
    Level(3), Woburn, MA
    *** DON'T SEND TECHNICAL QUESTIONS DIRECTLY TO ME, post them to newsgroups.
    Please DON'T copy followups to me -- I'll assume it wasn't posted to the group.
     
    Barry Margolin, Jul 21, 2003
    #8
  9. AC

    AC Guest

    On Mon, 21 Jul 2003 17:57:47 GMT,
    Barry Margolin <> wrote:
    > In article <>,
    > AC <> wrote:
    >>On Fri, 18 Jul 2003 21:39:36 GMT,
    >>Barry Margolin <> wrote:
    >>> In article <>,
    >>> AC <> wrote:
    >>>>On Fri, 18 Jul 2003 20:14:16 GMT,
    >>>>Barry Margolin <> wrote:
    >>>>> Yes. You would also normally change the subnet mask in the "ip address"
    >>>>> statement to 255.255.255.0.
    >>>>
    >>>>So the Ethernet1 config would like this?
    >>>>
    >>>>interface Ethernet1
    >>>> ip address 10.101.104.0 255.255.255.0
    >>>> no ip directed-broadcast
    >>>
    >>> Actually, the address needs to be in the range 10.101.104.1 through
    >>> 10.101.104.254. .0 is the network address and .255 is the broadcast
    >>> address.

    >>
    >>Okay. Can you give me an example of how the Interface commands should look?
    >>Sorry to be a pain, but I feel like I'm missing something here.

    >
    > interface Ethernet1
    > ip address 10.101.104.1 255.255.255.0


    Why do I suddenly feel like an idiot?

    Thanks for the help.

    --
    Aaron Clausen

     
    AC, Jul 21, 2003
    #9
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