Cisco Systems 4500 VLAN Mapping Configuration Guidelines

25-10
Software Configuration Guide—Release 15.0(2)SG
OL-23818-01
Chapter 25 Configuring 802.1Q Tunneling, VLAN Mapping, and Layer 2 Protocol Tunneling
Configuring VLAN Mapping
VLAN Mapping Configuration Guidelines
Guidelines include the following:
• Traditional QinQ uses 802.1Q tunnel ports; you configure one-to-one VLAN mapping and selectiv e
QinQ on 802.1Q trunk ports.
• To avoid mixing customer traffic, when you conf igure traditional Q-in-Q on a trunk port , you should
configure the service provider S-VLAN ID as an allowed VLAN on the trunk port.
• When you configure VLAN mapping on an EtherChannel, the mapping applies to all ports in the
port channel.
• You cannot configure encapsulation replicate on a SPAN destination port if the source port is
configured as a tunnel port or has a 1-to-2 mapping configured. Encapsulation replicate is supported
with 1-to-1 VLAN mapping.
• When configuring IEEE 802.1Q tunneling on an edge switch, you must use IEEE 802.1Q trunk ports
for sending packets into the service-provider network. However, packets going through the core of
the service-provider network can be carried through IEEE 802.1Q trunks, ISL trunks, or
nontrunking links. When IEEE 802.1Q trunks are used in these core switches, the native VLANs of
the IEEE 802.1Q trunks must not match any native VLAN of the nontrunking (tunneling) port on
the same switch. it is because traffic on the native VLAN is not tagged on the IEEE 802.1Q sending
trunk port.
• Ensure that the native VLAN for an IEEE 802.1Q trunk is the same on both ends of the trunk link.
If the native VLAN on one end of the trunk is different from the native VLAN on the other end,
spanning-tree loops might result.
• Layer 2 protocol tunneling must be configured for CDP, VTP, LLDP, or your switch detects the SP
switches, which is not desirable:
interface GigabitEthernet1/23
switchport mode trunk
switchport vlan mapping 1 dot1q-tunnel 311
switchport vlan mapping 31 dot1q-tunnel 311
l2protocol-tunnel cdp
l2protocol-tunnel lldp
l2protocol-tunnel vtp
• To process control traffic consistently, either enable Layer 2 protocol tunneling (recommended) or
insert a BPDU filter for spanning tree, as follows:
Current configuration : 153 bytes
!
interface FastEthernet9/1
switchport trunk native vlan 40
switchport mode trunk
switchport vlan mapping 10 20
spanning-tree bpdufilter enable
end
• If you need to merge CVLAN and SVLAN spanning tree topology, you do not need to configure
spanning-tree bpdufilter enable.
• To ensure consistent operation, do not use a native VLAN for translation.