9-73
Configuring Advanced Features
Port-Based Virtual LANs (Static VLANs)
Configuring Advanced
Features
To summarize:
Effect of VLANs on Other Switch Features
Spanning Tree Protocol Operation with VLANs
Because the Series 2500 switches follow the 802.1Q VLAN recommendation
to use single-instance spanning tree, STP operates across all ports on the
switch (regardless of VLAN assignments) instead of on a per-VLAN basis. This
means that if redundant physical links exist between the switch and another
802.1Q device, all but one link will be blocked, regardless of whether the
redundant links are in separate VLANs. However, you can use port trunking
to prevent STP from unnecessarily blocking ports (and to improve overall
network performance). Refer to “STP Operation with 802.1Q VLANs” on page
9-110.
Note that STP operates differently in different devices. For example, in the
(non-802.1Q) HP Switch 2000 and the HP Switch 800T, STP operates on a per-
VLAN basis, allowing redundant physical links as long as they are in separate
VLANs.
IP Interfaces
There is a one-to-one relationship between a VLAN and an IP network inter-
face. Since the VLAN is defined by a group of ports, the state (up/down) of
those ports determines the state of the IP network interface associated with
that VLAN. When a VLAN comes up because one or more of its ports is up, the
IP interface for that VLAN is also activated. Likewise, when a VLAN is
deactivated because all of its ports are down, the corresponding IP interface
is also deactivated.
VLANs Per
Port
Tagging Scheme
1 Untagged or Tagged. If the device connected to the port is 802.1Q-compliant,
then the recommended choice is “Tagged”.
2 or More 1 VLAN Untagged; all others Tagged
or
All VLANs Tagged
A given VLAN must have the same VID on any 802.1Q-compliant device in which the VLAN is
configured.
The ports connecting two 802.1Q devices should have identical VLAN configurations, as
shown for ports X2 and Y5, above.
