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Configuring MPLS Layer-2 VPNs
Layer-2 VPN Services
There are two basic types of Layer-2 VPN services. The first is a VLAN service. This
service transparently interconnects two or more VLAN segments together over an
MPLS network. The configured VLAN IDs for the customer switch interfaces are not
required to match, as long as the TLS egress LSR overwrites the VLAN tag with the
locally defined VLAN ID, or if the local VLAN is untagged, strips the 802.1Q tag
completely. The second service is a port service. This service transparently interconnects
two or more ports together over an MPLS network. Traffic is transported unmodified
between ports.
Extremeware supports both services, but only the VLAN service is interoperable with
other vendor implementations. Port-based TLS service requires that the dot1q tag
ethertype be configured to 9100. By changing the configured dot1q ethertype value, the
Ethernet switch ports treat 8100 tagged traffic as untagged and insert a new dot1q tag
with the configured ethertype value. By inserting a new dot1q tag, all traffic received on
a single port can be aggregated into a single VLAN and transported across an MPLS
domain as a VLAN service. All TLS edge switches must be configured to use the same
dot1q ethertype value.
MPLS VC Tunnels
MPLS virtual circuit (VC) tunnels are logical connections between two LERs over an
LSP. Like ATM VCs, these connections can be signaled ( dynamic) or statically
configured. Dynamic TLS tunnel connections are commonly referred to as VC tunnels,
because the TLS tunnel label is signaled based on the configured VC identifier (vcid).
The signaled VC label is used to create a two-label stack LSP. The outer label is the LSP
label obtained from LDP or RSVP-TE and the inner label is the signaled VC label. LERs
also signal the VC type when attempting to establish a VC tunnel. Extremeware only
supports the VLAN VC type and reject all other VC types, including the Ethernet VC
type used to signal Ethernet port service.
VLAN type VC tunnels are also referred to as TLS tunnels. Static TLS tunnels are not
signaled. The ingress and egress VC label for each TLS tunnel must be configured at
each end of the tunnel. Both static and dynamic TLS tunnels can be configured
simultaneously, but both share the same 16K TLS LER label space partition.
7-2
MPLS Module Installation and User Guide
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