Juniper JUNOSE 11.2.X BGP AND MPLS, Configuration Manual

Page: 558 / 742

MPLS next hop. The attributes of the shim interface are used to determine the
encapsulation parameters. These MPLS packets are later forwarded to the remote PE2
device. PE2 processes all the MPLS labels and determines that layer 2 processing is
required on the remaining layer 2 frames. After PE2 processes the Ethernet layer 2 frames,
they are forwarded to CE2.
Traffic arriving at PE1 from pseudowires is distributed across all the member links of the
LAG. The hashing algorithm, based on the VLAN identifier and source and destination
MAC addresses, is used to determine the physical link to which the packets must be
forwarded.
If you configure the Martini tunnel directly over LAG in the same topology as shown in
Figure 1, packet processing at PE1 remains the same as the case described. The only
difference is in processing the hash algorithm, which uses only the source and destination
MAC addresses, and not the VLAN identifier, to determine the physical link for transmission
of MPLS packets transmitted from the pseudowires.
If IP traffic is being transmitted from CE1, which is not designated for the MPLS L2VPN
tunnel, the packets arrive at an interface that is different from the one used for MPLS
traffic, VLAN2. This behavior occurs because the VLAN interface used for transmission
of IP traffic must be different from that used for MPLS traffic.
The MPLS shim interface can be configured directly over LAG or stacked on a VLAN
interface over LAG. For more information on the guidelines to be followed when you
configure the MPLS shim interface to enable MPLS Martini circuits to use LAG on the
CE-side devices, see “Multiple Layer 2 Services over MPLS Overview” on page 515.
Related Topics Example: Configuring MPLS L2VPN Tunnel over LAG on page 550
•
•
Example: Configuring MPLS L2VPN Tunnel over VLAN over LAG on page 546
Ethernet Raw Mode Encapsulation for Martini Layer 2 Transport Overview
An Ethernet pseudowire carries Ethernet/802.3 traffic over an MPLS network. JunosE
Software enables Ethernet traffic to be transmitted over Martini circuits (cross-connect
virtual circuits) on ES2 4G line modules (LMs), GE-2 LMs, GE/FE LMs, ES2 10G LMs, ES2
10G Uplink LMs, and ES2 10G ADV LMs. In previous releases, the transfer of Ethernet
packets over MPLS-based pseudowire enabled service providers to provide point-to-point
layer 2 Ethernet connectivity between geographically remote customer edge (CE) devices.
This functionality enabled the following tasks to be performed on received packets:
•
Removal of all V-LAN tags from layer 2 frames received from CE devices before
transmitting that frame to the pseudowire
• Replacement of all V-LAN tags in layer 2 frames received from the pseudowire with
the configured VLAN tags on the local interface before sending the frame to the CE
device
• Insertion of the inner V-LAN tag while sending layer 2 frames received from the
pseudowire to the CE device on a double-tagged interface
Copyright © 2010, Juniper Networks, Inc. 522
JunosE 11.2.x BGP and MPLS Configuration Guide