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=9704&t=9704 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]