IP address overlaps!

Discussion in 'Cisco' started by Dave, Feb 9, 2004.

  1. Dave

    Dave Guest

    Hi folks,

    I would like the following

    2Mb Leased Line
    |
    |
    195.192.x.1 255.255.255.248 Serial 0/0
    Cisco 3640
    195.192.x.2 255.255.255.248 Ethernet 0/0
    |
    |
    195.192.x.3 255.255.255.248
    Server

    From the Internet I would like to get to 195.192.x.3. But when on
    ethernet 0/0 I put in
    (config-if)ip address 195.192.x.2 255.255.255.248
    I get the following error:
    195.192.x.0 overlaps with Serial0/0

    Now I understanda little, I can't have the same network on 2 different
    interfaces, so how do I resolve this?

    Dave
     
    Dave, Feb 9, 2004
    #1
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  2. :I would like the following

    :2Mb Leased Line
    :|
    :195.192.x.1 255.255.255.248 Serial 0/0
    :Cisco 3640
    :195.192.x.2 255.255.255.248 Ethernet 0/0
    :|
    :195.192.x.3 255.255.255.248
    :Server

    :From the Internet I would like to get to 195.192.x.3. But when on
    :ethernet 0/0 I put in
    :(config-if)ip address 195.192.x.2 255.255.255.248
    :I get the following error:
    :195.192.x.0 overlaps with Serial0/0

    The easiest way for you to proceed would be to use NAT, so that the
    server is in a different IP address range that is mapped to 195.192.x.3
    by your 3640.

    If for some reason NAT is not acceptable, then you will have to either
    bridge between your ports, or else get the ISP to handle your IP address
    space differently.
     
    Walter Roberson, Feb 9, 2004
    #2
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  3. Dave

    Rik Bain Guest

    Another common solution would be to use ip unnumbered on the serial.

    int s0/0
    ip unnumbered ethernet0/0
    !
    int e0/0
    ip address 195.192.x.1 255.255.255.248
     
    Rik Bain, Feb 9, 2004
    #3
  4. Dave

    Dave Guest

    Cheers guys,

    sorry but I should have mentioned this.

    I have NAT outside on S0/0 and NAT inside on E0/0.

    So if I did......

    2Mb leased line
    |
    |
    IP unnumbered Serial 0/0 (NAT Outside)
    Cisco 3640
    195.192.x.1 255.255.255.248 Ethernet 0/0 (NAT Inside)
    |
    |
    HUB / Switch
    |
    |
    195.192.x.2 255.255.255.248
    Server

    I would then be able to connect to 195.192.x.2 ?

    cheers
    Dave
     
    Dave, Feb 9, 2004
    #4
  5. ~ sorry but I should have mentioned this.
    ~
    ~ I have NAT outside on S0/0 and NAT inside on E0/0.
    ~
    ~ So if I did......
    ~
    ~ 2Mb leased line
    ~ |
    ~ |
    ~ IP unnumbered Serial 0/0 (NAT Outside)
    ~ Cisco 3640
    ~ 195.192.x.1 255.255.255.248 Ethernet 0/0 (NAT Inside)
    ~ |
    ~ |
    ~ HUB / Switch
    ~ |
    ~ |
    ~ 195.192.x.2 255.255.255.248
    ~ Server
    ~
    ~ I would then be able to connect to 195.192.x.2 ?
    ~
    ~ cheers
    ~ Dave

    I don't know if that will work so well ... you want to
    have different outside vs. inside addresses so ...
    try it this way ...

    int loopback 0
    ip nat outside
    ip address 195.192.x.1 255.255.255.255
    int ser 0/0
    ip nat outside
    ip unnumbered loopback 0
    int eth 0/0
    ip nat inside
    ip address 195.192.x.2 255.255.255.248

    (and the server would be 195.192.x.3.)

    However, I don't understand something. Is 195.192.x.1 a globally valid
    IP address? I would assume so, since it's "nat outside". Then, are
    the other addresses in 195.192.x.0/29 globally valid or not? If they
    are valid: then why do you need NAT? If they are not: then you shouldn't
    be using them, as your use of these addresses will collide with the
    valid users of these addresses; instead you should use private addressing.

    Aaron

    ---

    ~
    ~ ~ > On Mon, 09 Feb 2004 11:37:06 -0600, Walter Roberson wrote:
    ~ >
    ~ > > In article <>, Dave
    ~ > > :I would like the following
    ~ > >
    ~ > > :2Mb Leased Line
    ~ > > :|
    ~ > > :195.192.x.1 255.255.255.248 Serial 0/0 Cisco 3640 195.192.x.2
    ~ > > :255.255.255.248 Ethernet 0/0
    ~ > > :|
    ~ > > :195.192.x.3 255.255.255.248
    ~ > > :Server
    ~ > >
    ~ > > :From the Internet I would like to get to 195.192.x.3. But when on
    ~ > > :ethernet 0/0 I put in
    ~ > > :(config-if)ip address 195.192.x.2 255.255.255.248 I get the following
    ~ > > :error:
    ~ > > :195.192.x.0 overlaps with Serial0/0
    ~ > >
    ~ > > The easiest way for you to proceed would be to use NAT, so that the
    ~ > > server is in a different IP address range that is mapped to 195.192.x.3
    ~ > > by your 3640.
    ~ > >
    ~ > > If for some reason NAT is not acceptable, then you will have to either
    ~ > > bridge between your ports, or else get the ISP to handle your IP address
    ~ > > space differently.
    ~ >
    ~ > Another common solution would be to use ip unnumbered on the serial.
    ~ >
    ~ > int s0/0
    ~ > ip unnumbered ethernet0/0
    ~ > !
    ~ > int e0/0
    ~ > ip address 195.192.x.1 255.255.255.248
    ~
     
    Aaron Leonard, Feb 10, 2004
    #5
  6. Dave

    Dave Guest

    Hi Aaron,

    the addresses are valid public IP's. They are used in a DMZ enviroment where
    there are 2 VPN's. I've been told I can only access the VPN's via their
    public IP's.

    The reason I require NAT is that my network on the other side of the DMZ use
    the 2mb leased line as their internet connection.

    I've attached a network diagram

    Cheers
    Dave
     
    Dave, Feb 10, 2004
    #6
  7. Dave

    mothupis

    Joined:
    Jun 22, 2007
    Messages:
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    195.192.x.0 overlaps with Serial0/0



    I think that has to do with your subnet mask, i'm new to networking and i also experienced the same problem few days back. What i did is that i changed my subnet mask last octet.

    Try use 255.255.255.252 not 255.255.255.248.

    That's if you've tried everything the guys mentioned with no success.
     
    mothupis, Jun 22, 2007
    #7
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