From: Dan (dp595@xxxxxxxxxxxxx)
Date: Sat Apr 14 2001 - 14:44:49 GMT-3
Eric,
The "down-when-looped" command was introduced to avoid this problem.
Both sides of the serial link should have the "down-when-looped" command
added to the Serial interface.
When either router detects a loop, it usually stays up/up, but when you have
the "down-when-looped" command, the interface goes to "up/down (looped)" so
that you can still see the loop but the router will remove any routes
referencing this interface from the routing table.
Dan Pontrelli
Customer Installation Engineer - Verio NYC
CCNP, MCSE, CNA
----- Original Message -----
From: "Eric Hauptman" <ehauptma@home.com>
To: "Groupstudy" <ccielab@groupstudy.com>
Sent: Saturday, April 14, 2001 3:51 AM
Subject: Re: Point to Point Serial link
> I would like to thank all those who responded to my point-to-point serial
link
> problem. I was informed tonight that our provider, AT&T, had a loop
somewhere
> in the telco pointing back to
> one end of the site, thus leaving one side up/down & the other side up/up.
>
> However, going forward, I'm perplexed about the best way to back this
circuit
> up using my current ISDN B-channels on the 2610 router. I had it setup to
use
> floating static routes with higher AD for the BRI channels, which works
fine as
> long as the serial drops on BOTH sides. What happened yesterday is that
when
> one side went down the floating static kicked in and the BRI was dialed.
> However, the other side's serial was still up/up, meaning the return
traffic
> was still being sent to the serial line, not the ISDN line, hence traffic
> couldn't pass. We manaully solved the problem by removing the floating
statics
> and putting all static routes on both sides pointing to the BRI lines.
>
> Does anyone have any ideas on the best way to deal with the situation in
the
> future? I assume some sort of dynamic routing protocal might be the
answer,
> but I was hoping to run this link without the added overhead of a routing
> protocol. Thanks.
>
> Eric H.
>
> Bob Dixon wrote:
>
> > Maybe a stupid question, but are you sure that your physical wiring is
in
> > place as it should be? In other words, maybe routerA's serial0 is cabled
to
> > a live circuit terminating on an unknown device that is exchanging
> > keepalives as it should. This would mean serial0 on routerA shows up/up.
Of
> > course, it is highly unlikely that you could ping across the wan link in
> > this scenario. routerB's serial 0 could be cabled to a cicuit that is
open
> > on the other end. That means serial 0 on routerB shows up/down. Just a
> > thought.
> >
> > >From a perspective that may sound more like PC troubleshooting than
router
> > troubleshooting, you could try powering down the router that shows
up/down,
> > re-seat the WIC card, and then boot the router. I just turned up some
t1's
> > and t3's the other day. We had a weird problem where the t1 wic showed
> > up/down (keepalive was set) and the ILEC could not loop the built-in csu
on
> > the WIC. After re-seating the WIC, the ILEC could latch the WIC and
after
> > dropping the loop, the circuit came up/up and ran clean.
> >
> > Bob
> >
> > ----- Original Message -----
> > From: Prashanth <prashanthcm@yahoo.com>
> > To: Curtis Call <curtiscall@home.com>; <ccielab@groupstudy.com>
> > Sent: Saturday, April 14, 2001 2:26 AM
> > Subject: RE: Point to Point Serial link
> >
> > > possible to send us the config?
> > >
> > >
> > > --- Curtis Call <curtiscall@home.com> wrote:
> > > > It might be that one side is expecting keepalives
> > > > and the other is not
> > > > expecting nor sending them.
> > > >
> > > >
> > > > >-----Original Message-----
> > > > >From: Eric Hauptman [mailto:ehauptma@home.com]
> > > > >Sent: Friday, April 13, 2001 2:25 AM
> > > > >To: Groupstudy
> > > > >Subject: OT: Point to Point Serial link
> > > > >
> > > > >
> > > > >I have a production network where one side of a
> > > > point to point serial
> > > > >link is showing up/down and the other side is
> > > > showing up/up. I thought
> > > > >that if one side went down they would both go down.
> > > > I know on frame
> > > > >relay one can be up/up and the other down, but I
> > > > thought on a point to
> > > > >point this would not be the case. Am I missing
> > > > something basic here? I
> > > > >am running the T1s into 2610 routers with built in
> > > > WIC-T1-CSUs.
> > > > >
> > > > >Thanks.
> > > > >
> > > > >Eric
> > > >
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