Configuring Mofrr; Information About Mofrr - Cisco Nexus 7000 Series Configuration Manual

Configuring MoFRR

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Configuring MoFRR

Information about MoFRR

Multicast only Fast Re-Route (MoFRR) is an IP solution that minimizes packet loss in a network when there
is a link or node failure. It works by making simple enhancements to multicast routing protocols like Protocol
Independent Multicast (PIM). It reduces multicast traffic disruption for the receivers in the event of Node or
Link failure anywhere along the Multicast Tree.
MoFRR transmits a multicast join message from a receiver toward a source on a primary path, while also
transmitting a secondary multicast join message from the receiver toward the source on a backup path. Data
packets are received from both the primary path and the secondary paths. The redundant packets are discarded
at topology merge points due to Reverse Path Forwarding (RPF) checks. When a failure is detected on the
primary path, the repair is made by changing the interface on which packets are accepted to the secondary
interface. Because the repair is local, it is fast—greatly improving convergence times in the event of node or
link failures on the primary path.
The MoFRR feature provides the ability to minimize packet loss in a network when there is a link or node
failure by enhancing, but not changing, multicast routing protocols such as PIM. With MoFRR, multicast
routing protocols do not have to wait or depend on unicast routing protocols to detect network failures.
The MoFRR feature can be divided into two planes, red and blue, that are fully disjoint from each other all
the way into the points of presence (POPs) as shown in the figure.
This two-plane design eliminates single points of failure in the core network. The upstream full-line arrows
indicate the normal path taken when the PIM joins the flow from the POPs toward the source of the network.
MoFRR adds the broken‐arrow path where the provider edge (PE) routers send an alternate PIM join to their
neighbor toward the source. Each PE router then receives two copies of the same stream, one from the blue
plane and one from the red plane. As a result of multicast RPF checks, the following occurs:
• The multicast stream received over the primary path (in the reverse direction of the full-line arrows) is
• The copy of the stream received on the alternate path (in the reverse direction of the broken-line arrows)
Configuring MoFRR, on page 179
accepted and forwarded to the downstream links.
is discarded.
C H A P T E R
Cisco Nexus 7000 Series NX-OS Multicast Routing Configuration Guide
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