INE R&S ATC009 - 802.1q Tunneling, Layer 2 Protocol Tunneling, EtherChannel over 802.1q Tunneling

802.1q Tunneling

• Layer 2 VPN over switched Ethernet network
– Lightweight version of MPLS L2VPN
• SP’s PE adds additional 802.1q tag to all frames received from CE
– Called “metro tag” or “QinQ”
• PE assigns all CE facing ports to the same VLAN
– One VLAN per customer in P network

• Configuration
– switchport mode dot1q-tunnel
• Tells switch to double tag frames
– switchport access vlan [vlan]
• Metro VLAN assignment
• Verification
– show dot1q-tunnel
• Cannot be dynamically negotiated

802.1q Tunneling Design Issues

• Assumes layer 2 network end-to-end
– PE –P –PE links must all run layer 2 trunking
– Implies scalability issues
• Additional tags increase payload size
– 4 bytes per tag
– Potential to exceed MTU of transit path
– Ethernet doesn’t support fragmentation
• Loss of control plane signaling for CE devices
– CDP, VTP, STP, etc. dropped by PE

Layer 2 Protocol Tunneling

• Used to tunnel Layer 2 Control Plane protocols between ports
– Typically used with 802.1q tunnel
• Support for…
– CDP
– VTP
– STP
– PAgP
– LACP
– UDLD

• Configuration
– l2protocol-tunnel [cdp| vtp | stp]
– l2protocol-tunnel point-to-point [lacp| pagp| udld]
• Verification
– show l2protocol-tunnel
– show l2protocol-tunnel summary

EtherChannel over 802.1q Tunnels

• CE can support aggregation of CE –PE links
– E.g.2 x GigE per customer site
• EtherChannel must be point-to-point
– Implies one metro tag per PE –CE link
• PE can tunnel negotiation as well
– l2protocol-tunnel point-to-point [lacp| pagp]

Ethernet Troubleshooting

• Build the network in a modular fashion
• Always test layer 3 reachability before adding advanced options
• Use SVIs to simulate hosts

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Catalyst 3560 Switch Software Configuration Guide, Rel. 12.2(46)SE

- Configuring IEEE 802.1Q and Layer 2 Protocol Tunneling

-- Understanding Layer 2 Protocol Tunneling
http://www.cisco.com/en/US/docs/switches/lan/catalyst3560/software/release/12.2_46_se/configuration/guide/swtunnel.html#wp1005050