SMC Networks SMC6624M manual Effect of VLANs on Other Switch Features, IP Interfaces, To summarize

Configuring Advanced Features

Port-Based Virtual LANs (Static VLANs)

To summarize:

VLANs Per	Tagging Scheme
Port

1Untagged 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.

Effect of VLANs on Other Switch Features

Spanning Tree Protocol Operation with VLANs

Because the SMC6624M switch follows 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 9-107.

Note that STP operates differently in different devices. For example, in some switches, 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.

Features Configuring Advanced

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