Specifications

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Catalyst 4500 Series Switch Cisco IOS Command Reference—Release IOS XE 3.3.0XO(15.1(1)XO)
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Chapter 2 Cisco IOS Commands for the Catalyst 4500 Series Switches
ip multicast multipath
ip multicast multipath
To enable load splitting of IP multicast traffic over Equal Cost Multipath (ECMP), use the
ip multicast multipath command in global configuration mode. To disable this functionality, use the no
form of this command.
ip multicast [vrf vrf-name] multipath [s-g-hash {basic | next-hop-b ased }]
no ip multicast [vrf vrf-name] multipath [s-g-hash {basic | next-hop-based}]
Syntax Description
Command Default If multiple equal-cost paths exist, multicast traffic will not be load-split across those paths.
Command Modes Global c onfiguratio n (config)
Usage Guidelines The ip multicast multipath command does not work with bidirectional Protocol Independent Multicast
(PIM).
Use the ip multicast multipath command to enable load splitting of IP multicast traffic across multiple
equal-cost paths.
If two or more equal-cost paths from a source are available, unicast traffic will be load-split across those
paths. However, by default, multicast traffic is not load-split across multiple equal-cost paths. In general,
multicast traffic flows down from the reverse path forwarding (RPF) neighbor. According to the PIM
specifications, this neighbor must have the highest IP address if more than one neighbor has the same
metric.
When you configue load splitting with the ip multicast multipath command, the system splits multicast
traffic across multiple equal-cost paths based on source address using the S-hash algorithm. When the
ip multicast multipath command is configured and multiple equal-cost paths exist, the path in which
multicast traffic will travel is selected based on the source IP address. Multicast traffic from different
sources will be load-split across the different equal-cost paths. Load splitting will not occur across
equal-cost paths for multicast traffic from the same source sent to different multicast groups.
Note The ip multicast multipath command load splits the traffic but does not load balance the traffic. Traffic
from a source will use only one path, even if the traffic greatly exceeds traffic from other sources.
vrf vrf-name (Optional) Enables ECMP multicast load splitting for I P multicast traffic
associated with the Multicast Virtual Private Network (MVPN) routing and
forwarding (MVRF) instance specified for the vrf-name argument.
s-g-hash basic |
next-hop-based
(Optional) Enables ECMP multicast load splitting based on source and group
address or on source, group, and next-hop address.
The basic keyword enables a s imple hash ba sed on source and group addr ess.
This algorithm is referred to as the basic S-G-hash algorithm.
The next-hop-based keyword enables a more complex hash based on source,
group, and next-hop address. This algorithm is referred to as the
next-hop-based S- G-hash al gorithm.