
52 Troubleshooting
gateway channel is used. If reported packet loss is in the ‘tx‘ direction, the
fourth parameter is the IP address of the IP Phone that detected packet
loss in the incoming stream.
Perform the following tasks:
•
Verify the ports of the router/switch the TLAN and IP Phone are
connected to are configured as one of the following (in highest to least
desirable order):
—
Autonegotiation: this is the recommended setting. The
VGMC/Signaling Server TLAN interface and the IP Phone
autosense the speed and autonegotiate the half or full duplex
setting. Setting the switch or router port to do the same means the
fastest possible connection negotiate without intervention.
— Manual setting: 100BaseT, half duplex
— Manual setting: 10BaseT, half duplex
Note: The SMC card TLAN interface supports 10BaseT and
100BaseT half and full duplex, while the ELAN supports only
10BaseT half duplex. The IP Phones support 10BaseT or 100BaseT
half duplex and 10BaseT full duplex.You cannot manually configure
a port on the switch or router to 10BaseT or 100BaseT full
duplex and have an error-free connection to the IP Phones or
VGMC/Signaling Server.
Manual configuration turns off autonegotiation in nearly every product
on the market. By definition of the standards, without autonegotiation,
the VGMC, Signaling Server and IP Phones revert to half duplex
operation. This means the switch or router will be in a full duplex
mode while the VGMC device is in a half duplex mode, a situation
guaranteed to cause packet loss. If the switch port is set to half duplex
and sees lots of late collisions and duplicate collisions or if it is in full
duplex mode and sees lots of CRC Errors or runt frames then odds are
there is a mismatch.
•
Check the router statistics to see the amount of network traffic on each
subnet and the number of discarded packets.
• Check for differences in subnet configurations (that is, full versus half
duplex or 10BaseT vs 100BaseT) if the problem occurs only for some
IP Phones and not others.
• Check which QoS mechanism is enabled on the router to give priority
to the packet traffic from the IP Phones.
• To eliminate packet loss messages, configure the switch or router for
10BaseT half duplex operation and check if that eliminates the packet
loss messages. If the messages stop, check the wiring and ensure the
site has CAT-5 cable.
Nortel Communication Server 1000
Troubleshooting Guide for Distributors
NN43001-730 02.02 31 December 2009
Copyright © 2008-2009 Nortel Networks. All Rights Reserved.
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