Brocade Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide (Supporting R05.6.00) - Manual (Page 475)

Multi-Service IronWare Multiprotocol Label Switch (MPLS) Configuration Guide 451
53-1003031-02
How VPLS works
3
VPLS can be used to transport Ethernet frames to and from multiple, geographically dispersed
sites belonging to a customer Virtual Private Network (VPN). The Provider Edge (PE) devices
connecting the customer sites provide functions similar to a Layer 2 switch. The PE devices learn
the MAC addresses of locally connected customer devices, flood broadcast and unknown unicast
frames to other PE devices in the VPN, and create associations between remote MAC addresses
and the VC Label Switch Patches (LSPs) used to reach them.
Figure 53 shows an illustration of a VPLS configuration with two customer VPNs. Two separate
VPLS instances have been created, one for Customer A’s VPN and one for Customer B’s VPN. A
VPLS instance consists of a full mesh of VC LSPs between the customers’ PE devices. In the
example, Customer A's VPLS instance consists of VC LSPs between routers R1, R2, and R3.
Customer B’s VPLS instance consists of VC LSPs between routers R3 and R4. Because VC LSPs are
unidirectional, separate VC LSPs exist in each direction between each of the PE devices. When
Label Distribution Protocol (LDP) is enabled on the MPLS interfaces on the PE devices, the VC LSPs
are established automatically through LDP when the user specifies the VPLS peers on the PE
devices.
Alternatively, LSPs can be established using Resource ReSerVation Protocol- Traffic Engineering
(RSVP-TE) by manually configuring LSPs to all PE devices. The same LSP from one PE to another PE
can be shared by multiple VPLS instances for traffic belonging to different customers. In this case,
traffic belonging to different customers has the same tunnel label, but different VC labels. When
more than one LSP exists from one PE to another PE for multiple VPLS instances, traffic belonging
to the different VPLS instances are load-balanced across the LSPs. In this case, traffic belonging to
the different VPLS instances has different tunnel and VC labels.
In Figure 53, the VPLS instance for Customer A links its CE devices so that they appear to be a
single Layer 2 broadcast domain. The VPLS instance for Customer B has two VLANs configured
within the VPLS instance, VLAN 100 and VLAN 200. The VPLS instance for Customer B has two
endpoints on PE device R4. Unlike a Virtual Leased Line (VLL), a VPLS instance can have multiple
endpoints. The PE device performs local and remote VLAN tag translation, so that multiple VLANs
are specified under a single VPLS instance.
FIGURE 53 Sample VPLS configuration