A L2VPN network
enables service providers (SPs) to provide L2 services to geographically
disparate customer sites. Typically, a SP uses an access network to connect the
customer to the core network. This access network may use a mixture of L2
technologies, such as Ethernet and Frame Relay. The connection between the
customer site and the nearby SP edge router is known as an attachment circuit
(AC). Traffic from the customer travels over this link to the edge of the SP
core network. The traffic then tunnels through a pseudowire over the SP core
network to another edge router. The edge router sends the traffic down another
AC to the customer's remote site.
The L2VPN feature
enables the connection between different types of L2 attachment circuits and
pseudowires, allowing users to implement different types of end-to-end
services.
Note |
BOOTP traffic (dst UDP 68) over any type of pseudowire is unsupported.
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Cisco IOS XR software
supports a point-to-point end-to-end service, where two Ethernet circuits are
connected together. An L2VPN Ethernet port can operate in one of two modes:
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Port Mode—In this mode, all packets reaching the port are sent over the pseudowire, regardless of any VLAN tags that are present
on the packets. In VLAN mode, the configuration is performed under the l2transport configuration mode.
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VLAN Mode—Each VLAN on a CE (customer edge) or access network to PE (provider edge) link can be configured as a separate L2VPN
connection (using either VC type 4 or VC type 5). To configure L2VPN on VLANs, see The Carrier Ethernet Model chapter in this manual. In VLAN mode, the configuration is performed under the individual sub-interface.
Switching can take
place in the following ways:
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AC-to-PW—Traffic reaching the PE is tunneled over a PW (pseudowire) (and conversely, traffic arriving over the PW is sent
out over the AC). This is the most common scenario.
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Local switching—Traffic arriving on one AC is immediately sent out of another AC without passing through a pseudowire.
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PW stitching—Traffic arriving on a PW is not sent to an AC, but is sent back into the core over another PW.
Note |
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If your network requires that packets are transported transparently, you may need to modify the packet’s destination MAC (Media
Access Control) address at the edge of the Service Provider (SP) network. This prevents the packet from being consumed by
the devices in the SP network.
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The encapsulation dot1ad
vlan-id and encapsulation dot1ad
vlan-id
dot1q any commands cannot co-exist on the same physical interface or bundle interface. Similarly, the encapsulation dot1q
vlan-id and encap dot1q
vlan-id
second-dot1q any commands cannot co-exist on the same physical interface or bundle interface. If there is a need to co-exist, it is recommended
to use the exact keyword in the single tag encapsulation. For example, encap dot1ad
vlan-id
exact or encap dot1q
vlan-id
exact.
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In an interface which already has QinQ configuration, you cannot configure the QRangeinQ sub-interface where outer VLAN range
of QRangeinQ overlaps with outer VLAN of QinQ. Attempting this configuration results in the splitting of the existing QinQ
and QinQRange interfaces. However, the system can be recovered by deleting a recently configured QinQRange interface.
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In an interface which already has QinQRange configuration, you cannot configure the QRangeinQ sub-interface where outer VLAN
range of QRangeinQ overlaps with inner VLAN of QinQRange. Attempting this configuration results in the splitting of the existing
QinQ and QinQRange interfaces. However, the system can be recovered by deleting a recently configured QinQRange interface.
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You can use the
show interfaces
command to display AC and pseudowire information.
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