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Help! Trying to assign WAN IP to Cisco 877

Discussion in 'Routing & Switching' started by leohopkins, Jul 21, 2010.

  1. leohopkins

    leohopkins New Member

    Hi Guys,

    I am trying to set up a Cisco 877 router on an ADSL circuit but am having difficulties as I do not know which IP address I am supposed to assign on the outside of the router (WAN IP)

    the information I have about the circuit is as follows:


    Correct IP:
    Mask IP:

    IP Range:
    Subnet Mask:
    Router IP:
    Usable IPs: -

    On my old router (an old Zyxel) I used with a mask. no problems !

    With the cisco 877 is is not letting me assign the above address for my public IP as it is a network ID and will not work. (The router wont accept it)

    any ideas?

    : - )
  2. BosonMichael
    Highly Decorated Member Award

    BosonMichael Yottabyte Poster

    You have already diagnosed the problem: is indeed a network address and cannot be used as a host address. Doesn't matter what your old Zyxel let you do... Cisco routers won't allow that (and the Zyxel shouldn't). You need to assign your router a host address in that range - one that the next-hop router isn't using.

    Out of curiosity, why are you using routable IP addresses for your LAN instead of non-routable, RFC 1918 IP addresses?
    Last edited: Jul 21, 2010
    Certifications: CISSP, MCSE+I, MCSE: Security, MCSE: Messaging, MCDST, MCDBA, MCTS, OCP, CCNP, CCDP, CCNA Security, CCNA Voice, CNE, SCSA, Security+, Linux+, Server+, Network+, A+
    WIP: Just about everything!
  3. leohopkins

    leohopkins New Member

    Hmmmm.......very strange stuff, there was a fault on the line anyway which has now been resolved and now ive managed to get the .200 address assigned and working on the WAN interface. PPP is weird !!

    No idea regarding the routable IP's, this was just what we were assigned by the ISP for extra range.

    Thanks for your advice : - )
    Last edited: Jul 21, 2010
  4. Spice_Weasel

    Spice_Weasel Kilobyte Poster

    BTW, you don't need to use your internal interface for the extra address space from your ISP. Just set up the nat rules on the external interface. This can give you more visibilty and control of traffic entering your network.

    Certifications: CCNA, CCNP, CCIP, JNCIA-ER, JNCIS-ER,MCP

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