Effect Of Vlans On Other Switch Features; Spanning Tree Operation With Vlans; Ip Interfaces - HP procurve series 4100gl Management And Configuration Manual

Port-Based Virtual LANs (VLANs) and GVRP
Port-Based Virtual LANs (Static VLANs)
11-30
VLAN 20 (Management VLAN)
VLAN 1
VLAN 40
Even though the ports on the Management VLAN link between Switch 1 and Switch 2 do not belong
to the other VLANs connecting the two switches, enabling Spanning Tree will block one of the two
links. This is because Spanning Tree operates per-switch and not per-VLAN.
Figure 11-23. Example of Inadvertently Blocking a Management VLAN Link by
Implementing Spanning Tree

Effect of VLANs on Other Switch Features

Spanning Tree Operation with VLANs

Because the Series 4100GL switches follows the 802.1Q VLAN recommenda-
tion to use single-instance spanning tree, Spanning Tree 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 Spanning Tree from unnecessarily blocking ports
(and to improve overall network performance). Refer to "Spanning Tree
Operation with 802.1Q VLANs" on page 13-4.
Note that Spanning Tree operates differently in different devices. For example,
in the (obsolete, non-802.1Q) HP Switch 2000 and the HP Switch 800T, Span-
ning Tree 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
VLAN 1
VLAN 40
Switch
1
Switch
2
VLAN 20 Only
(Management VLAN)
Blocked