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VPLS Labels and VLAN Tags

Consider the VPLS network shown in Figure 8.

Figure 8: VLAN Tags and VPLS Labels

Image g016827.gif

The L2 PE routers are MX-series routers. Each site is connected to two P routers for redundancy, although both links are only shown for L2-PE1 at Site 1. Site 1 is connected to P0 and P1, Site 2 is connected to P0 and P2 (not shown), Site 3 is connected to P2 and P3, and Site 4 is connected to P1 and P3. VPLS pseudowires configured on the PE and P routers carry traffic between the sites.

The pseudowires for the VPLS instances are shown with distinct dashed and dotted lines. The VLANs at each site are:

L2-PE1 at Site 1: VLAN 100 and VLAN 300
L2-PE2 at Site 2: VLAN 100
L2-PE3 at Site 3: VLAN 100
L2-PE4 at Site 4: VLAN 300

Service provider SP-1 is providing VPLS services for customer C1 and C2. L2-PE1 is configured with a VPLS instance called customer-c1-vsi. The VPLS instance sets up pseudowires to remote Site 2 and Site 3. L2-PE1 is also configured with a VPLS instance called customer-c2-vsi. The VPLS instance sets up a pseudowire to remote Site 4.

The following is the configuration of interfaces, virtual switches, and bridge domains for MX-series router L2-PE1:



[edit]
interfaces ge-1/0/0 {
encapsulation flexible-ethernet-services;
flexible-vlan-tagging;


unit 1 {
encapsulation vlan-vpls;
vlan-id 100;
}




unit 11 {
encapsulation vlan-vpls;
vlan-id 301;
}


}
interfaces ge-2/0/0 {
encapsulation flexible-ethernet-services;
flexible-vlan-tagging;


unit 1 {
encapsulation vlan-vpls;
vlan-id 100;
}


}
interfaces ge-3/0/0 {
encapsulation flexible-ethernet-services;
flexible-vlan-tagging;


unit 1 {
encapsulation vlan-vpls;
vlan-id 200; # Should be translated to normalized VLAN
value
}


}
interfaces ge-6/0/0 {
encapsulation flexible-ethernet-services;
flexible-vlan-tagging;


unit 11 {
encapsulation vlan-vpls;
vlan-id 302;
}


}

routing-instances {


customer-c1-vsi {
instance-type vpls;
vlan-id 100;
interface ge-1/0/0.1;
interface ge-2/0/0.1;
interface ge-3/0/0.1;
} # End of customer-c1-vsi




customer-c2-vsi {
instance-type vpls;
vlan-id none; # This will remove the VLAN tags from packets
sent on VPLS for customer 2
interface ge-1/0/0.11;
interface ge-6/0/0.11;
} # End of customer-c2-vsi


} # End of routing-instances

Consider the first VLAN for customer C1. The vlan-id 100 statement in the VPLS instance called customer-c1-vsi sets the normalized VLAN to 100. All packets sent over the pseudowires have a VLAN tag of 100.

The following happens on VLAN 100 as a result of this configuration:

Packets received on logical interfaces ge-1/0/0.1 or ge-2/0/0.1 with a single VLAN tag of 100 in the frame are accepted.
Packets received on logical interface ge-3/0/0.1 with a single VLAN tag of 200 in the frame are accepted and have their tag values translated to the normalized VLAN tag value of 100.
Unknown source MAC addresses and unknown destination MAC addresses are learned based on their normalized VLAN values of 100.
All packets sent on the VPLS pseudowire have vlan-id 100 in their VLAN tag fields.

Now consider the second VLAN for Customer C2. The vlan-id none statement in the VPLS instance called customer-c2-vsi removes the incoming VLAN tags before the packets are sent over the VPLS pseudowires.

The following happens on the C2 VLAN as a result of the vlan-id none configuration:

A MAC table is created for each instance of vlan-id none. All MAC addresses learned over the interfaces belonging to this VPLS instance are added to this table. The received or configured VLAN tags are not considered when the MAC addresses are added to this table. This is a case of shared VLAN learning.
Packets with a single VLAN tag value of 301 are accepted on interface ge-1/0/0.11. The VLAN tag value 301 is then popped and removed from the frame of this packet.
Packets with a single VLAN tag value of 302 are accepted on interface ge-6/0/0.11. The VLAN tag value 302 is then popped and removed from the frame of this packet.
All packets sent on pseudowires will not have any VLAN tags used to identify the incoming Layer 2 logical interface.

Note: The packet can still contain other customer VLAN tags.
Packets received from pseudowires are looked up in the MAC table associated with the VPLS instance. Any customer VLAN tags in the frame are ignored.

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