From: Dan (dp595@xxxxxxxxxxxxx)
Date: Sat Apr 14 2001 - 17:23:52 GMT-3
If the loop points toward router 1, router 2 will not detect the loop.
Router 2 "should" lose carrier detect and consequently be down/down due to
the break in the circuit. "Down-when-looped" only helps on the router the
loop is pointing towards.
The other router that the loop is "not" pointing towards should go down hard
when the circuit is broken, and if not you may have a clocking problem. I
would ask the telco why you are still receiving carrier detect on the side
of the circuit that has been broken.
They should be able to see what is happening on the line.
I've seen all kinds of weird problems like this and it is often attributed
to some faulty or misoptioned equipment somewhere along the line.
Just remember, that if your interface is up/up when is should be down/down
and you are certain that you are not providing the clocking, you'll have to
find out where it's coming from. This entails working with the telco by
starting at their nearest testing point to that end of the circuit.
Dan Pontrelli
Customer Installation Engineer - Verio NYC
CCNP, MCSE, CNA
----- Original Message -----
From: "Eric Hauptman" <ehauptma@home.com>
To: "Dan" <dp595@optonline.net>; "Chuck Larrieu" <chuck@cl.cncdsl.com>;
"Groupstudy" <ccielab@groupstudy.com>
Sent: Saturday, April 14, 2001 2:44 PM
Subject: Re: Point to Point Serial link
> Dan,
>
> Thanks for the info. However, even though I didn't have the command on
either
> serial interface, one side was up/down while the other was up/up. Are you
> saying that if, for example, router 1 detects a loop, that same loop will
be
> detected by router 2? It seems to me that if the telco sends a loop
pointing
> towards router 1 the "down-when-looped" command will do its job and detect
the
> serial being down and drop the route from the routing table. However, how
will
> router 2 know about the loop pointing to router 1? Won't router 2 think
> everything is just great and leave the serial in its normal up/up state?
Or
> will router 2 notice that there is a loop somewhere in the network and
change
> it's status to up/down, just like router 1?
>
>
> Eric
>
> Dan wrote:
>
> > 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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