[Asterisk-Users] Weird LAN VoIP Echo

[Brent Franks]

Hi everyone,

This one has me baffled....

We installed 16 Polycom IP 500 Phones in January on an Asterisk Server:
	3.0Ghz
	768MB of Ram
	30GB Harddrives
	10/100/1000 NIC

Our Lan setup is like this:
	3 Netgear FS526T Switches
		2 10/100/1000 Mbps copper gigabit ports
		24 10/100 Mbps ports 
	100Mbps out to phones
	the 1Gig ports connect the switches together, and one gig port
	goes to the Asterisk Softswitch

Reinvite is set to no on the phones because the IP500's couldnt handle it
would die...  Users report echo on the LAN-LAN calls, if they place calls
on the same switch, up to the second floor, third floor, etc.  Basically
there is no pattern that emerges, other than the fact that the calls are
still routed through the server.

The weird part is, the echo has just started in the last 3 weeks.  Doing
an analysis of the network (sniffing) shoes nothing weird, no bugs, worms,
etc.. Also, ping times are constantly at:

64 bytes from 10.10.60.15: icmp_seq=1 ttl=64 time=2.22 ms
64 bytes from 10.10.60.15: icmp_seq=2 ttl=64 time=1.17 ms

I can't figure out why this is occuring.  Lan-lan calls should have ZERO
echo?  I can understand why we're experiencing it with the PSTN, but not
all digital calls.

We're also using Ulaw codec, and I have tried A law and have the same
result.

Any assistance or ideas of how to trouble shoot would be greatly
appreciated, because I have racked my brain for three weeks working on
this...

Anything, please anything :)

Thanks

- Brent