Avaya 8800 Planning And Engineering page 102

Layer 2 loop prevention
Figure 31: One STG between two Layer 3 devices and one Layer 2 device
To provide load sharing over links X and Y, create a configuration with multiple STGs that are
transparent to the Layer 2 device and that divide the traffic over different VLANs. To ensure
that the multiple STGs are transparent to the Layer 2 switch, the BPDUs for the two new STGs
(STG2 and STG3) must be treated by the Ethernet Switch as regular traffic, not as BPDUs.
In the configuration in
page 103, the BPDUs generated by the two STGs (STG2 and STG3) are forwarded by the
Ethernet Switch 8100. To create this configuration, you must configure STGs on the two
Ethernet Routing Switch 8800/8600s, assign specific MAC addresses to the BPDUs created
by the two new STGs, create VLANs 4002 and 4003 on the Layer 2 device, and create two
new VLANs (VLAN 2 and VLAN 3) on all three devices.
102 Planning and Engineering — Network Design
Figure 32: Alternative configuration for STG and Layer 2 devices on
November 2010