Reference Guide

Service Provider Bridging | 899
VLAN Stacking with C-Series and S-Series
The default TPID for the outer VLAN tag is 0x9100. Beginning with FTOS version 8.2.1.0, both the
C-Series and S-Series allow you to configure both bytes of the 2-byte TPID. Previous versions allowed
you to configure the first byte only, and thus, the systems did not differentiate between TPIDs with a
common first byte. For example 0x8100 and any other TPID beginning with 0x81 were treated as the same
TPID, as shown in Figure 49-6. Versions 8.2.1.0 and later differentiate between 0x9100 and 0x91XY, as
shown in Figure 49-8.
You can configure the first eight bits of the TPID using the command
vlan-stack protocol-type.
The TPID on the C-Series and S-Series systems is global. Ingress frames that do not match the system
TPID are treated as untagged. This rule applies for both the outer tag TPID of a double-tagged frame and
the TPID of a single-tagged frame.
For example, if you configure TPID 0x9100, then the system treats 0x8100 and untagged traffic the same
and maps both types to the default VLAN, as shown by the frame originating from Building C in
Figure 49-8. For the same traffic types, if you configure TPID 0x8100, then the system is able to
differentiate between 0x8100 and untagged traffic and maps each to the appropriate VLAN, as shown by
the packet originating from Building A in Figure 49-8.
Therefore, a mismatched TPID results in the port not differentiating between tagged and untagged traffic.
Figure 49-6. Single and Double-tag TPID Match on the C-Series and S-Series
I
N
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E
R
N
E
T
S
E
R
V
I
C
E
P
R
O
V
I
D
E
R
VL
AN GREE
N
, VLAN PURP
L
E
VLAN G
REEN
VL
AN PURPLE
VL
AN
BLUE
VLAN RED
V
LAN R
E
D
VL
A
N
BLU
E
TPID
(0x8100)
PCP
CFI
(0)
VID
(VLAN Red)
TPID
(0x8100)
PCP
CFI
(0)
VID
(VLAN Red)
TPID
(0x8100)
PCP
CFI
(0)
VID
(VLAN Purple)
Building A
Building B
R2-C-Series
TPID: 0x8100
R1-C-Series
TPID: 0x8100
R4-Non-Force10 System
TPID: 0x8100
TPID 0x8100
R3-C-Series
TPID: 0x8100
Building D
Building C