Manual

Layer 2 Tunnel Protocol Version 3
Information About Layer 2 Tunnel Protocol Version 3
19
Cisco IOS Releases 12.0(29)S and 12.2(25)S
Supported L2TPv3 Payloads
L2TPv3 supports the following Layer 2 payloads that can be included in L2TPv3 packets tunneled over
the pseudowire:
• Frame Relay
• Ethernet
• 802.1q (VLAN)
• HDLC
• PPP
• ATM
• IPv6 Protocol Demultiplexing
Note Each L2TPv3 tunneled packet includes the entire Layer 2 frame of the payloads described in this section.
If sequencing is required (see the section “Sequencing”), a Layer 2-specific sublayer (see the section
“Pseudowire Control Encapsulation”) is included in the L2TPv3 header to provide the Sequence Number
field.
Frame Relay
L2TPv3 supports the Frame Relay functionality described in the following sections:
• Port-to-Port Trunking
• DLCI-to-DLCI Switching
• PVC Status Signaling
• Sequencing
• ToS Marking
• CIR Guarantees
• Binding L2TPv3 Sessions to Multilink Frame Relay Interfaces
Port-to-Port Trunking
Port-to-port trunking is where two CE Frame Relay interfaces are connected as by a leased line (UTI
“raw” mode). All traffic arriving on one interface is forwarded transparently across the pseudowire to
the other interface.
For example, in Figure 1, if the two CE routers are connected by a virtual leased line, the PE routers
transparently transport all packets between CE R3 and CE R4 over a pseudowire. PE R1 and PE R2 do
not examine or change the DLCIs, and do not participate in the LMI protocol. The two CE routers are
LMI peers. There is nothing Frame Relay-specific about this service as far as the PE routers are
concerned. The CE routers should be able to use any encapsulation based on HDLC framing without
needing to change the provider configuration.
DLCI-to-DLCI Switching
Frame Relay DLCI-to-DLCI switching is where individual Frame Relay DLCIs are connected to create
an end-to-end Frame Relay PVC. Traffic arriving on a DLCI on one interface is forwarded across the
pseudowire to another DLCI on the other interface.