3Com 1000 - Manual (Page 128)

C-4 A PPENDIX C: T ROUBLE - SHOOTING
You have added the Switch 1000 to an already
busy network, and response times and traffic
levels have increased:
You may have added a group of users to one of the
Switch 1000 ports via a repeater or switch, and not
turned off IFM. Turn off IFM on any port that is con-
nected to multiple devices. Refer to
“Setting Up the
Switch Ports” on page 4-12 .
You have connected an endstation directly to
the Switch and the endstation fails to boot cor-
rectly:
The Switch has STP enabled, and the endstation is
booting before the STP initialization process is com-
plete. Specify that the port has Fast Start enabled,
and then reboot the endstation. For more informa-
tion about specifying Fast Start for a port, refer to
“Configuring the STP Parameters of Ports” on page
5-20 .
The Switch keeps ageing out endstation entries
in the Switch Database (SDB):
The Switch has STP enabled, and STP is instructing
the Switch to age entries in the SDB faster because
topology changes are occurring in the network.
1 Reduce the number of topology changes by
enabling Fast Start for all ports which are directly
connected to an endstation; refer to
“Configuring
the STP Parameters of Ports” on page 5-20 .
2 Specify that the endstation entries are Non-ageing;
refer to
“Setting Up the Switch Database (SDB)” on
page 4-16 .
3 If the network has less than 500 addresses, specify
that the bridging mode of the Switch is set to For-
ward to All; refer to
“Setting Up the Switch Unit”
on page 4-9 .
4 Consider disabling STP on the Switch, and using
resilient links to provide network resilience; refer to
“Enabling STP on the Switch” on page 5-17 and
“Setting Up Resilient Links” on page 4-19 .
You are trying to manage the Switch over a
network which has STP, and you are losing con-
tact with the management agent intermit-
tently:
As shown in Figure C-1 , there is a SuperStack II
Switch unit (Switch A) between your management
workstation and the Switch 1000 (Switch B). You
have configured more than one VLAN on both
Switch units, and there is a parallel STP path for
each VLAN between the Switch units.
When Switch B transmits BPDUs across a VLAN
other than VLAN 1, Switch A learns the MAC
address of Switch B through the port on that
VLAN. The management agent of Switch B is only
accessible through VLAN 1, and so your manage-
ment workstation cannot communicate with Switch
B until it transmits BPDUs across VLAN 1. When that
occurs, Switch A learns the MAC address of Switch
B through the port on VLAN 1.