3Com 5500 SI - Switch - Stackable, Configuration Manual

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118 C
HAPTER
8: VLAN-VPN C
ONFIGURATION
Adjusting the TPID
Values of VLAN-VPN
Packet
Tag protocol identifier (TPID) is a portion of the VLAN tag field. IEEE 802.1Q specifies
the value of TPID to be 0x8100.
Figure 30 illustrates the structure of the Tag field of an Ethernet frame defined by IEEE
802.1Q.
Figure 30 The structure of the Tag field of an Ethernet frame
As for S5600 series switches, the value of the TPID field is 0x8100, which is defined by
IEEE 802.1Q. Other vendors use other TPID values (such as 0x9100 or 0x9200) in the
outer tags of VLAN-VPN packets.
To be compatible with devices coming from other vendors, S5600 series switches can
adjust the TPID values of VLAN-VPN packets. You can configure TPID value for ports
connecting to the public networks to enable these ports to forward received packets
after replacing the TPID values carried in the outer VLAN tags of the received packets
with the user-defined TPID value, through which the VLAN-VPN packets sent to public
networks can be recognized by devices of other vendors.
VLAN-VPN
Configuration
This section contains configuration information for VLAN-VPN.
Configuration
Prerequisites
■
GARP VLAN registration protocol (GVRP), GARP multicast registration protocol
(GMRP), expandable resilient networking (XRN), neighbor topology discovery
protocol (NTDP), spanning tree protocol (STP) and 802.1x protocol are disabled on
the port.
■
The port is not a VLAN-VPN uplink port.
CAUTION: By default, STP and NTDP are enabled on a device. You can disable
these two protocols using the stp disable and undo ntdp enable commands.
Configuration procedure
Table 106 Configure the VLAN-VPN function for a port
Operation Command Description
Enter system view system-view -
Enter Ethernet port view interface
interface-type
interface-number -
Enable the VLAN-VPN
function vlan-vpn enable Required
By default, the VLAN-VPN function is disabled
on a port.The VLAN-VPN function is applicable
to access ports only.