3Com 8807 Configuration Manual page 859

# Disable the STP protocol and enable VLAN-VPN on Ethernet3/1/3.
[Switch_D] interface Ethernet3/1/2
[Switch_D-Ethernet3/1/2] stp disable
[Switch_D-Ethernet3/1/2] vlan-vpn enable
[Switch_D-Ethernet3/1/2] quit
# Set Ethernet3/1/3 to a trunk port and add this port to all the VLANs.
[Switch_D] interface Ethernet3/1/3
[Switch_D-Ethernet3/1/3] port link-type trunk
[Switch_D-Ethernet3/1/3] port trunk permit vlan all
c
CAUTION:
STP must be enabled on VLAN-VPN tunnel-enabled devices; otherwise BPDUs
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in the user network cannot be transmitted transparently.
VLAN-VPN-enabled ports must be configured to Access ports. The link type of
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the intermediate operator's network must be configured to the Trunk link.
You cannot configure VLAN-VPN tunnel on the ports where DOT1X, GVRP, STP,
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or NTDP is enabled.
VLAN-VPN Tunnel Configuration 859