Cisco Catalyst 3560-X

1-10
Catalyst 3750-X and 3560-X Switch Software Configuration Guide
OL-25303-03
Chapter 1 Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling
Understanding Layer 2 Protocol Tunneling
Figure 1-5 Layer 2 Network Topology without Proper Convergence
In an SP network, you can use Layer 2 protocol tunneling to enhance the creation of EtherChannels by
emulating a point-to-point network topology. When you enable protocol tunneling (PAgP or LACP) on
the SP switch, remote customer switches receive the PDUs and can negotiate the automatic creation of
EtherChannels.
For example, in Figure 1-6, Customer A has two switches in the same VLAN that are connected through
the SP network. When the network tunnels PDUs, switches on the far ends of the network can negotiate
the automatic creation of EtherChannels without needing dedicated lines. See the “Configuring Layer 2
Tunneling for EtherChannels” section on page 1-15 for instructions.
Figure 1-6 Layer 2 Protocol Tunneling for EtherChannels
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Customer X
virtual network
VLANs 1 to 100
Sw i t c h A
VLAN 17
VLAN 18
VLAN 19
VLAN 20
VLAN 17
VLAN 18
VLAN 19
VLAN 20
Sw i t c h B
Sw i t c h C
Se r v i c e
Pr o v i d e r
EtherChannel 1
Cu st o m er A
Site 1
Cu st o m er A
Site 2
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Sw i t c h D
EtherChannel 1
Tr u n k
Asymmetric link