Chapter 2 Network configuration 61

Because there is only one link between the two switches, the Spanning Tree Protocol (STP) treats this configuration as any other switch-to-switch connection. For this configuration to work properly, both switches must support the 802.1Q tagging protocol.

VLANS spanning multiple untagged switches

Figure 18 shows VLANs spanning multiple untagged switches. In this configuration, Switch S2 does not support 802.1Q tagging and you must use a single switch port on each switch for each VLAN.

For this configuration to work properly, you must set spanning tree participation to Disabled (the STP is not supported across multiple LANs).

Figure 18 VLANs spanning multiple untagged switches

VLAN 1

 

 

 

VLAN 2

 

 

 

 

 

S1

BayStack 420

Untagged ports

 

S2

Non-802.1Q

 

tagging switch

10005EA

When the STP is enabled on these switches, only one link between each pair of switches will be forwarding traffic. Because each port belongs to only one VLAN at a time, connectivity on the other VLAN is lost. Exercise care when configuring the switches to ensure that the VLAN configuration does not conflict with spanning tree configuration.

Using the BayStack 420 10/100/1000 Switch

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Nortel Networks 1000ASE-XD manual Vlans spanning multiple untagged switches, VLANs spanning multiple untagged switches