About Broadcast And Multicast Routing; About Multicast Root Switch; Setting The Multicast Root Switch - Cisco AP775A - Nexus Converged Network Switch 5010 Configuration Manual

FSPF Routes
S e n d d o c u m e n t a t i o n c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m

About Broadcast and Multicast Routing

Broadcast and multicast in a Fibre Channel fabric uses the concept of a distribution tree to reach all
switches in the fabric.
FSPF provides the topology information to compute the distribution tree. Fibre Channel defines 256
multicast groups and one broadcast address for each VSAN. Switches in the Cisco MDS 9000 Family
only use broadcast routing. By default, they use the principal switch as the root node to derive a loop-free
distribution tree for multicast and broadcast routing in a VSAN.
All switches in the fabric should run the same multicast and broadcast distribution tree algorithm to
Caution
ensure the same distribution tree.
To interoperate with other vendor switches (following FC-SW3 guidelines), the SAN-OS and NX-OS
4.1(1b) and later software uses the lowest domain switch as the root to compute the multicast tree in
interop mode.

About Multicast Root Switch

By default, the native (non-interop) mode uses the principal switch as the root. If you change the default,
be sure to configure the same mode in all switches in the fabric. Otherwise, multicast traffic could face
potential loop and frame-drop problems.
The operational mode can be different from the configured interop mode. The interop mode always uses
Note
the lowest domain switch as the root.

Setting the Multicast Root Switch

To use the lowest domain switch for the multicast tree computation using Fabric Manager, follow these
steps:
Expand a fabric, expand a VSAN, and then select Advanced for the VSAN that you want to configure
Step 1
FSPF on.
You see the advanced Fibre Channel configuration in the Information pane.
Select the Multicast Root tab.
Step 2
You see the multicast root configuration in the Information pane as shown in
Cisco MDS 9000 Family Fabric Manager Configuration Guide
32-14
Chapter 32 Configuring Fibre Channel Routing Services and Protocols
OL-17256-03, Cisco MDS NX-OS Release 4.x
Figure 32-12.