Problem has been resolved. I found the problem after taking Symon's suggestion of checking that I did no accidently trying to apply a network or broadcasxt address to the interface. I found that one of the addresses I was trying to use was the network address of another interface. Thanks, for all the responds everyone. ""Rik Guyler"" wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... > Well, since you say you have everything else accounted for, have you tried > rebooting the router? Subinterfaces and loopbacks tend to be rather > troublesome once setup. Deleting and changing these virtual interfaces > typically requires a reboot for the changes to take effect completely. > > You might also check that "ip subnet-zero" is turned on. If not, you will > get that very message if you try to use the zero subnet. > > Rik > > -----Original Message----- > From: tazman [mailto:[EMAIL PROTECTED]] > Sent: Sunday, June 24, 2001 5:10 PM > To: [EMAIL PROTECTED] > Subject: Setting up Sub-interfaces on serial interface for Frame Relay > [7:9697] > > > I am having a problem when attempting to configure sub-interfaces for a > Frame Relay connection and was wondering if anyone has ever seen this > problem before. I configured two routers for a point-to-point Frame Relay > circuit with sub-interfaces and performed a test and turn-up with AT&T which > worked fine. The problem I am having is I realized after I configured the > interfaces on both routers that I had used the wrong IP addresses. I setup > both ends of the circuit with a subnet address of 255.255.255.252 but when I > attempted to change the address I get a bad subnet mask error. I have both > routers configured as IP Classless and was able to assign a /30 address to > both earlier. I removed the IP address from the interfaces and tried to add > a new address and I get the same thing. Is there something special with > sub-interfaces or Frame Relay which is causing this problem? Any suggestions > would be greatly appreciated. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=9881&t=9881 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]