3Com 1100 - Manual (Page 222)

222 C HAPTER 11: P ROBLEM S OLVING
You have specified that an endstation generates traffic that has a
high priority, but when it passes through the network this priority
information is lost. The endstation is attached to a Switch port using an
untagged VLAN connection, and the Switch is removing the priority
information when it is forwarded to other untagged ports. To maintain
the priority information, specify that all untagged Switch ports use
802.1Q tagging.
You have placed two or more Switch units in a stack, and some
ports have lost their VLAN allocations and been disabled. The
Switch units had more than 16 VLANs defined between them, and these
extra VLANs were removed when the units were stacked. If a port was
allocated to one of these VLANs among others, it lost that particular
VLAN allocation. If a port only belonged to removed VLANs, it lost all its
VLAN allocations and was disabled. Re-enable the disabled ports, and
place them in the remaining VLANs.
You have connected a Switch to a device using an 802.1Q tagged
link, and you can no longer access the management software of
the device or the devices connected to that device. You may have
connected to a device that only supports 802.1Q tagged links and have
not specified that VLAN 1 traffic uses 802.1Q tagging. Specify that
VLAN 1 traffic is 802.1Q tagged, and try accessing the devices again.
You have connected an endstation that does not support IEEE
802.1Q to the Switch. When you specify that the Switch port
belongs to an untagged VLAN, the endstation does not appear to
be connected to that VLAN. The port may have been placed in the
VLAN using 802.1Q tagging, and the Switch is only transmitting the
VLAN traffic with 802.1Q tags. Remove the 802.1Q tagging for the port,
and try again.
Your Switch should be operating as an IGMP Querier, but it is not
sending query packets to the network. Check that:
■
The Switch does not have the IP address 0.0.0.0. If it does, change the
IP address, and re-enable IGMP Multicast Learning.
■
The network is only using the Default VLAN (VLAN 1). The Switch can
only act as the querier in the Default VLAN.