4A0-105: Nokia Virtual Private LAN Services

VPLS is a multipoint Layer 2 VPN that interconnects multiple sites as a single bridged Ethernet domain. It emulates LAN bridging functions, including MAC address learning, across the connected sites.

For multiple active SDPs toward the far-end PE, SR OS selects the SDP template with the best metric. SDP 10 has metric 5, the lowest metric among the available SDPs.

Traditional Layer 2 designs require loop prevention to avoid bridging loops, and their spanning-tree-based control plane can converge slowly after a topology change. VLAN scalability is also constrained by the 12-bit IEEE 802.1Q VLAN identifier, which supports VLAN IDs 1 through 4094; IDs 0 and 4095 are reserved.

Shorter MAC aging timers remove learned FDB entries sooner when traffic is intermittent. A destination whose entry has aged out is unknown and is normally flooded, so lowering the age time increases the likelihood of unknown-traffic flooding. Nokia recommends setting the remote-age timer longer than the local-age timer to reduce such flooding.

H-VPLS scales VPLS by keeping PEs fully meshed within each metro VPLS domain and using point-to-point spoke SDPs to interconnect the metro domains. This eliminates the need for a single full mesh among all PEs across the combined network.