3Com Switch 7750 Configuration Guide

Protocol-Based VLAN 93
The switch differentiates between 802.2 LLC encapsulation and 802.3 SNAP
encapsulation according to the values of the DSAP field and the SSAP field.
n
When the OUI is 00-00-00 in 802.2 SNAP encapsulation, the PID field has the
same meaning as the type field in Ethernet II encapsulation, which both refer to
globally unique protocol number. Such encapsulation is also known as SNAP
RFC1042 encapsulation, which is standard SNAP encapsulation. The SNAP
encapsulation mentioned in this chapter refers to SNAP RFC 1042 encapsulation.
Procedure for the Switch
to Judge Packet Protocol
Figure 33 Procedure for the switch to judge packet protocol
Encapsulation Formats
Receive
packets
Type(Length)
field
Ethernet II
ncapsulation
Match the
type value
Invalid packets
that cannot be
matched
802.2/802.3
encapsulation
Control
field
Invalid packets
that cannot be
matched
dsap/ssap
value
802.2 SNAP
encapsulation
Match the
dsap/ssap value
802.2 LLC
encapsulation
Match the
type value
802.3 raw
encapsulation
0x05DD to 0x05FF0x0600 to 0xFFFF
0 to 0x05DC
Value is not 3
Value is 3
Both are AABoth are FF
Other values
Receive
packets
Type(Length)
field
Ethernet II
ncapsulation
Match the
type value
Invalid packets
that cannot be
matched
802.2/802.3
encapsulation
Control
field
Invalid packets
that cannot be
matched
dsap/ssap
value
802.2 SNAP
encapsulation
Match the
dsap/ssap value
802.2 LLC
encapsulation
Match the
type value
802.3 raw
encapsulation
0x05DD to 0x05FF0x0600 to 0xFFFF
0 to 0x05DC
Value is not 3
Value is 3
Both are AABoth are FF
Other values
Table 45 Encapsulation formats
Encap Protocol
Ethernet
II 802.3 raw 802.2 LLC
802.2
SNAP Type value
IP Supported Not
supported
Not
supported
Supported 0x0800
IPX Supported Supported Supported Supported 0x8137
AppleTalk Supported Not
supported
Not
supported
Supported 0x809B