Cisco Catalyst 4500 Series Configuration Manual page 393

Chapter 2
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.
If the ip multicast multipath command is configured with the s-g-hash keyword and multiple
equal-cost paths exist, load splitting will occur across equal-cost paths based on source and group
address or on source, group, and next-hop address. If you specify the optional s-g-hash keyword for load
splitting IP multicast traffic, you must select the algorithm used to calculate the equal-cost paths by
specifying one of the following keywords:
•
•
Examples The following example shows how to enable ECMP multicast load splitting on a router based on source
address using the S-hash algorithm:
Switch(config)# ip multicast multipath
The following example shows how to enable ECMP multicast load splitting on a router based on source
and group address using the basic S-G-hash algorithm:
Switch(config)# ip multicast multipath s-g-hash basic
The following example shows how to enable ECMP multicast load splitting on a router based on source,
group, and next-hop address using the next-hop-based S-G-hash algorithm:
Switch(config)# ip multicast multipath s-g-hash next-hop-based
basic—The basic S-G-hash algorithm is predictable because no randomization is used in calculating
the hash value. The basic S-G-hash algorithm, however, is subject to polarization because for a given
source and group the same hash is always chosen irrespective of the router that the hash is being
calculated on.
next-hop-based—The next-hop-based S-G-hash algorithm is predictable because no randomization
is used to determine the hash value. Unlike the S-hash and basic S-G-hash algorithms, the
next-hop-based hash mechanism is not subject to polarization.
Catalyst 4500 Series Switch Cisco IOS Command Reference—Release XE 3.9.xE and 15.2(5)Ex
ip multicast multipath
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