I have three serial ports, each a T1 link, that are showing up/up. I've bundled the three into a single multilink interface. The multilink is showing down/down. Debugging ppp authentication doens't show any problems. "show ppp multilink" shows no active bundles, and all three serial links are listed as inactive, along with the multilink.
Looking at each serial port, each is showing "Encapsulation PPP, LCP Open, multilink closed". I've double-checked each serial ports multilink group settings, and they match the multilink interfaces group number.
I can post the config, but it's very basic, with no fancy tricks. It's a very simple Internet-facing router, w/o any routing protocols, only a single default route, and no access lists applied anywhere.
I'd appreciate any ideas on this. Thanks.