Basic MVR Deployment

Because MVR is primarily targeted for IPTV and similar applications, a basic deployment for that application is shown in the following figure. In the figure, an IPTV server is connected through a router to a network of switches. Switch 1 has three customer VLANs, Vlan2, Vlan3, and Vlan4. The multicast streams are delivered through the network core (Metro Ethernets), which often use a ring topology and some kind of redundant protection to provide high availability. For example, McastVlan forms a ring through switches Switch1 through Switch4. The link from Switch2 to Switch4 is shown as blocked, as it would be if some form of protection (such as EAPS (Extreme Automatic Protection Switching)) is used.
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Basic MVR Deployment
Without MVR, there are two ways to distribute multicast streams in this topology:
  • Extend subscriber VLANs (Vlan2, Vlan3, and Vlan4) to the network core, by tagging the ports connecting the switches.
  • Configure all VLANS with an IP address and run PIM or DVMRP on each switch.

There are problems with both of these approaches. In the first approach, multiple copies of the same stream (IPTV channel) would be transmitted in the core, wasting bandwidth. In the second approach, all switches in the network core would have to be Layer 3 multicast aware, and would have to run a multicast protocol. Typical network cores are Layer 2 only.

MVR provides a simple solution to this problem If McastVlan in Switch1 is configured with MVR, it leaks the traffic into the local subscriber VLANs that contain hosts that request the traffic. For simple cases, perform these configuration steps:
  • Configure MVR on McastVlan.
  • Configure an IP address and enable IGMP (Internet Group Management Protocol) and IGMP snooping on the subscriber VLANs (by default IGMP and IGMP snooping are enabled on Extreme Networks‘ switches).
  • For all the multicast streams (IPTV channels), configure static IGMP snooping membership on the router on McastVlan.
  • Enable MVR on the switches in the network.


MVR works best with IGMPv1 and IGMPv2. We recommend that you do not use MVR with IGMPv3.

The strategy above conserves bandwidth in the core and does not require running PIM on the subscriber switches.

In this topology, a host (for example, a cable box or desktop PC) joins a channel through an IGMP join message. Switch1 snoops this message and adds the virtual port to the corresponding cache's egress list. This is possible because an MVR enabled VLAN can leak traffic to any other VLAN. When the user switches to another channel, the host sends an IGMP leave for the old channel and a join for the new channel. The corresponding virtual port is removed from the cache for the old channel and is added to the cache for the new channel.

As discussed in Static and Dynamic MVR, McastVlan also proxies IGMP joins learned on other VLANs to the router. On an MVR network it is not mandatory to have a router to serve the multicast stream. All that is required is to have a designated IGMP querier on McastVlan. The IPTV server can also be directly connected to McastVlan.