3Com Switch 7750 Configuration Guide Guide

Protocol-Based VLAN 87
In 802.2 SNAP encapsulation format, the values of the DSAP field and the SSAP
field are always AA, and the value of the control field is always 3.
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 29 Procedure for the switch to judge packet protocol
Encapsulation Formats
Implementation of
Protocol-Based VLAN
Switch 7750 Family Ethernet switches assign the packet to the specific VLAN by
matching the packet with the protocol template.
Both are AA
Both are FF
Dsap
ssap
snap
llc
Match dsap
and ssap value
Match
type
Other values
snap
llc
snap
llc
snap
llc
Receive packets
Type (length ) field
0x600
0 to 0x05DC
0x6000x6000x600
0x05DC to 0x0600
Invalid packets that
cannot be matched
802.3 encapsulation
Control
field
Invalid packets that
cannot be matched
Value is 3
Value is not 3
snap
llc
Raw
encapsulation
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap encapsulation
llc encapsulation
0x6000x6000x600
Ethernet II
encapsulation
Match the
type value
0x600 to 0xFFF
Control
Both are AA
Both are FF
Dsap
ssap
snap
llc
Match dsap
and ssap value
Match
type
Other values
snap
llc
snap
llc
snap
llc
Both are AA
Both are FF
Dsap
ssap
snap
llc
Match dsap
and ssap value
Match
type
Other values
snap
llc
snap
llc
snap
llc
Dsap
ssap
snap
llc
Match dsap
and ssap value
Match
type
Other values
snap
llc
snap
llc
snap
llc
Receive packets
Type (length ) field
0x600
0 to 0x05DC
0x6000x6000x600
0x05DC to 0x0600
Invalid packets that
cannot be matched
802.3 encapsulation802.3 encapsulation
Control
field
Invalid packets that
cannot be matched
Value is 3
Value is not 3
snap
llc
Raw
encapsulation
snap
llc
snap
llc
snap
llc
snap
llc
Raw
encapsulation
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap encapsulation
llc encapsulation
0x6000x6000x600
Ethernet II
encapsulation
Match the
type value
0x600 to 0xFFF
Control
Both are AA
Both are FF
Dsap
ssap
snap
llc
Match dsap
and ssap value
Match
type
Other values
snap
llc
snap
llc
snap
llc
Both are AA
Both are FF
Dsap
ssap
snap
llc
Match dsap
and ssap value
Match
type
Other values
snap
llc
snap
llc
snap
llc
Dsap
ssap
snap
llc
Match dsap
and ssap value
Match
type
Other values
snap
llc
snap
llc
snap
llc
Receive packets
Type (length ) field
0x600
0 to 0x05DC
0x6000x6000x600
0x05DC to 0x0600
Invalid packets that
cannot be matched
802.3 encapsulation802.3 encapsulation
Control
field
Invalid packets that
cannot be matched
Value is 3
Value is not 3
snap
llc
Raw
encapsulation
snap
llc
snap
llc
snap
llc
snap
llc
Raw
encapsulation
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap encapsulation
llc encapsulation
0x6000x6000x600
Ethernet II
encapsulation
Match the
type value
0x600 to 0xFFF
Control
Both are AA
Both are FF
Dsap
ssap
snap
llc
Match dsap
and ssap value
Match
type
Other values
snap
llc
snap
llc
snap
llc
Dsap
ssap
snap
llc
Match dsap
and ssap value
Match
type
Other values
snap
llc
snap
llc
snap
llc
Both are AA
Both are FF
Dsap
ssap
snap
llc
Match dsap
and ssap value
Match
type
Other values
snap
llc
snap
llc
snap
llc
Dsap
ssap
snap
llc
Match dsap
and ssap value
Match
type
Other values
snap
llc
snap
llc
snap
llc
Receive packets
Type (length ) field
0x600
0 to 0x05DC
0x6000x6000x600
0x05DC to 0x0600
Invalid packets that
cannot be matched
802.3 encapsulation802.3 encapsulation
Control
field
Invalid packets that
cannot be matched
Value is 3
Value is not 3
snap
llc
Raw
encapsulation
snap
llc
snap
llc
snap
llc
snap
llc
Raw
encapsulation
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap
llc
snap encapsulation
llc encapsulation
0x6000x6000x600
Ethernet II
encapsulation
Match the
type value
0x600 to 0xFFF
Control
Table 36 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