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Cisco SDM not accepting subnet mask

Dan560 asked
Medium Priority
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?
Watch Question

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

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


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.
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.

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.

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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