Reference Guide

870 | Service Provider Bridging
www.dell.com | support.dell.com
Figure 43-13. VLAN Stacking without L2PT
You might need to transport control traffic transparently through the intermediate network to the other
region. Layer 2 Protocol Tunneling enables BPDUs to traverse the intermediate network by identifying
frames with the Bridge Group Address, rewriting the destination MAC to a user-configured non-reserved
address, and forwarding the frames. Since the frames now use a unique MAC address, BPDUs are treated
as normal data frames by the switches in the intermediate network core. On egress edge of the intermediate
network, the MAC address rewritten to the original MAC address and forwarded to the opposing network
region (Figure 43-14).
FTOS Behavior: In FTOS versions prior to 8.2.1.0, the MAC address that Dell Force10 systems use to overwrite
the Bridge Group Address on ingress was non-configurable. The value of the L2PT MAC address was the Dell
Force10-unique MAC address, 01-01-e8-00-00-00. As such, with these FTOS versions, Dell Force10 systems are
required at the egress edge of the intermediate network because only FTOS could recognize the significance of
the destination MAC address and rewrite it to the original Bridge Group Address. In FTOS version 8.2.1.0 and
later, the L2PT MAC address is user-configurable, so you can specify an address that non-Dell Force10 systems
can recognize and rewrite the address at egress edge.
I
N
T
E
R
N
E
T
S
E
R
V
R
I
C
E
P
R
O
V
I
D
E
R
w
/
ww
S
P
A
P
P
N
N
I
N
G
T
R
E
E
S
P
A
P
P
N
N
I
N
G
T
R
E
E
N
E
T
W
O
R
K
S
P
A
P
P
N
N
I
N
G
T
R
E
E
T
R
E
E
Building A
Building B
X
BPDU w/ destination
MAC address: 01-80-C2-00-00-00
no spanning-tree
no spanning-tree