impossible circuit

Jay Hennigan jay at
Sun Aug 17 01:57:06 CDT 2008

Is this only happening in one direction?  One possibility is that the 
carrier has a different circuit that is provisioned up, HDLC, with no 
physical connection.  A short-circuit in a DACS or MUX is bridging the 
transmit interface towards your destination with a transmit interface on 
the unused but active circuit.  This would cause your traffic in that 
direction to fork both on the desired path and some rogue path that 
eventually gets routed to your destination.

The ethernet equivalent would be a SPAN monitor port plumbed to a 
transmit-only interface on a different network.

Definitely a strange one.  If I'm correct, when the other circuit starts 
to get customer traffic things will probably break completely for either 
the new customer seeing your PPP traffic or for both of you.

Jay Hennigan - CCIE #7880 - Network Engineering - jay at
Impulse Internet Service  -
Your local telephone and internet company - 805 884-6323 - WB6RDV

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