Cisco SDM not accepting subnet mask

Posted on 2009-02-11
Last Modified: 2012-05-06
I have just been given a fixed I.P address and subnet mask by my isp but when I configure on my cisco 837 through sdm I receive a message saying
Please enter a valid IP address and a subnet mask.

I am certain that what I have put in is correct. Is it possible to configure the connection manually though telnet or something?
Question by:Dan560
    LVL 28

    Accepted Solution

    Are you certain that the IP address they gave you is the address to be assigned to your router, or could it be the base address of the network?

    Example: is not a valid IP address with that subnet mask.  The usable IP addresses are
    LVL 28

    Expert Comment

    If you will provide the last number in the IP address and the subnet mask, we can tell you the range of valid addresses.
    LVL 2

    Author Comment

    the last number in the ip address is 47 and the subnet mask is
    this is the email they sent maybe you will understand it better.

    Other set up details as needed:-
    VPI setting:  0   VCI setting: 38 Protocol  PpoA Encapulation  VCMux
    MTU  1432 is optimal, however other values will work.
    Subnet mask: (Dynamic IP standard)
    *Static IP:
    1 Static IP:, 4 Static IPs:
    8 Static IPs:, 16 Static IPs:
    *Static IP addresses are ordered separately to your main order. If you have ordered static IP addresses then one of the above static IP subnet masks that relates to your static IP order will have to be configured for your service to work. Conformation relating to any static IP addresses ordered will be sent separately.
    LVL 8

    Assisted Solution

    See this guide for subnetting:

    The subnet mask you would need is

    This allows for 2 usable IP addresses, one of which is assigned to you, the other is the default gateway which is the router of your ISP.
    LVL 8

    Expert Comment

    The other thing I could suggest:

    "Subnet mask: (Dynamic IP standard) "
    May mean set your IP Address to dynamic?

    I still think the subnet should be correct though.
    LVL 8

    Expert Comment

    Not sure what its called on SDM since I don't use it, but the command to set the ip to dynamicly assigned is:

    ip address negotiated

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