"Howard C. Berkowitz" wrote: > > I wasn't aware of that! Thanks. > > But isn't loop detection also a PPP option? > Yes, it's described as part of RFC1661, but it might be a catch-22. The magic number field used for this is optional and must be negotiated. Cisco routers do attempt magic number negotiation and do detect looped paths, and .... let me check current doc... DO maintain a line protocol up status as long as "down-when-looped" has NOT been configured. So you're quite right -- for Cisco to Cisco, PPP and HDLC will both treat this the same way. OTOH, if the encapsulation were frame-relay or some other, then a loop causes a line protocol down state (e.g., LMI or ILMI polling fails). With Cisco to non-Cisco, particularly Ascend Pipelines, I have seen the magic number negotiation fail, and the Cisco reported a loop condition because the Ascend was echoing back the packet with the Cisco's magic number. But that was a while back. So thanks, Howard, for responding! - Marty > At 10:16 PM 2/19/2001 -0500, Marty Adkins wrote: > >"Howard C. Berkowitz" wrote: > > > > > > HDLC really doesn't offer any advantages over PPP, so it really > > > reflects someone who doesn't want to do minimum reconfiguration of > > > their Ciscos to worry about using PPP for multivendor compatibility. > > > > >Well, one small advantage is that Cisco's proprietary HDLC keepalive > >will report a loop condition on the layer 1. And it will also, by > >default, treat a looped interface as "line protocol up", which is > >great for testing, using just the router. > > > > Marty Adkins Email: [EMAIL PROTECTED] > > Mentor Technologies Phone: 240-568-6526 > > 133 National Business Pkwy WWW: http://www.mentortech.com > > Annapolis Junction, MD 20701 Cisco CCIE #1289 _________________________________ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
