Allied Telesis AT-9000 Series - Manual (Page 851)

AT-9000 Switch Command Line User’s Guide
Section III: File System 823
when they exit the network. The inner VID is native to the packets, but is
ignored by the metro provider network.
Figure 144. Metro Provider 802.1Q Header in Tagged Packets
VLAN stacking may also be used with untagged ports, which do not
contain 802.1Q headers. The new header is added after the source MAC
address and remains in the packets only while the packets are being
transported across a metro network. The headers are deleted at the point
the packets leave the metro network and reenter the customer networks.
Figure 145. Metro Provider 802.1Q Header in Untagged Packets
Note
To maintain the best performance of a network in a metro
environment and to avoid packet flooding on the ports on the switch,
you should try to limit the number of network nodes to less than
8,000 devices, which is the maximum size of the switch’s MAC
address table.