Extreme Networks ExtremeWare XOS Guide Manual page 233

Tunneling (VMANs)
VMAN is enabled on the ports in the tunnel. When VMAN is enabled on a network port, that port adds
the VMAN tag to all ingressing frames, whether the frame is originally tagged or untagged. The
Ethernet type configured for the VMAN header applies to the entire switch; this value cannot be
configured per port. The default VMAN Ethernet type on Extreme Networks devices is 0x88a8.
If your VMAN transits a third-party device (other than an Extreme Networks device), you must
configure the EtherType as the Ethernet type that the third-party device uses.
The system adds a 4-byte VMAN header on all packets, both originally tagged and untagged packets
arriving at the VMAN port. Beginning with ExtremeWare XOS 11.3, the system supports all VMAN
EtherTypes, including the standard VLAN Ethernet type of 0x8100.
The VMAN tunnel begins at the ingress, or customer access, port and terminates at the egress, or trunk,
port. Traffic flows from the egress trunk port onto the network thereafter without the VMAN tag.
Ensure that all the switch-to-switch ports in the VMAN tunnel are configured as tagged ports.
Configure the VMAN ingress, or customer access, port as an untagged port (although this port does
accept tagged packets). You must configure the VMAN tunnel egress, or trunk, port as an untagged port
so that the VMAN header is stripped from the frame.
NOTE
You must configure the VMAN tunnel egress, or trunk, port as untagged so that the VMAN header is stripped from
the frame.
Each tunnel port that accesses the user can support (or belong to) only one VMAN tunnel; the remaining
ports throughout the VMAN tunnel can support many VMANs.
VMANs on the BlackDiamond 8800 Family of Switches and the Summit X450
Switch Only
You must enable jumbo frames prior to configuring the VMANs on the BlackDiamond 8800 family of
switches (formerly known as Aspen) and the Summit X450 switch. On these switches, you enable jumbo
frames on the entire switch; you cannot enable jumbo frames on separate ports. See Chapter 5 for more
information on configuring jumbo frames on these devices.
On the BlackDiamond 8800 family of switches, you cannot configure both VLANs and VMANs on the
same slot; all ports on each slot must belong exclusively to either VLANs or VMANs. If you do
configure both VLANs and VMANs on the same slot, the system returns an error message. The VMAN
can span multiple modules, but you cannot configure VLANs and VMANs on the same module.
On the Summit X450 switch, you cannot configure both VLANs and VMANs on the same switch; all
ports on each discrete Summit X450 switch must belong exclusively to either VLANs or VMANs.
You can configure the BlackDiamond 8800 family of switches and the Summit X450 switch to use the
802.1p value on the inner tag to direct the packet to the appropriate QoS queue on the egress port. See
"QoS Queue on Egress Port" for more information on this feature.
VMANs on the BlackDiamond 10K Switch Only
The system automatically enables the specified ports for jumbo frames when you add ports to the
VMANs.
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ExtremeWare XOS 11.3 Concepts Guide