Huawei quidway s7700 - Page 367

Networking Requirements
RPF check is the basis of route selection and unicast routes are used to forward multicast traffic.
According to RPF check, a unique route is selected to forward multicast data. If multicast traffic
is heavy, network congestion may occur and multicast services are affected. Multicast load
splitting is an extension of the multicast route selection rule and is independent of RPF check.
If there are multiple optimal equal-cost routes on a network, they may be used to forward
multicast data. Multicast traffic can be load balanced amount multiple equal-cost routes.
Currently, multicast load splitting can be performed based on the source address, group address,
and source group address, without meeting requirements of load splitting in all the scenarios. If
multicast routing entries and network configurations are stable, RPF interfaces and RPF
neighbors in the entries remain unchanged. If a few multicast routing entries are used, traffic
among equal-cost routes may be distributed unevenly.
The stable-preferred multicast load splitting policy offsets the disadvantages of the preceding
load splitting policies. As shown in Figure 9-3, three equal-cost routes are available from Switch
E connected to HostA to the multicast source. The stable-preferred multicast load splitting policy
is configured on Switch E so that entries are evenly distributed to the three equal-cost routes.
Load splitting among equal-cost routes is implemented.
If forwarding capabilities or traffic congestion degrees of the three equal-cost routes of Switch
E are different, multicast entries cannot be load balanced. You need to configure uneven load
splitting on Switch E, set different load splitting routes for upstream interfaces, and change the
number of multicast entries on the equal-cost routes. In this manner, multicast entries on the
equal-cost routes can be controlled flexibly.
Figure 9-3 Networking diagram for configuring multicast load splitting
SwitchA
GE1/0/0
GE2/0/2
G
E
2
/
0
/
3
G
E
2
/
0
/
1
G
E
1
/
0
/
0
GE1/0/0
G
E
1
/
0
/
0
SwitchB
SwitchC
SwitchD
G
E
1
/
0
/
1
G
E
2
/
0
/
0
GE2/0/0
G
E
2
/
0
/
0
GE1/0/2
G
E
1
/
0
/
3
GE2/0/0
Loopback0
HostA
Source
SwitchE
PIM-SM
Switch
Interface IP Address Device Interface IP Address
Switch A GE1/0/0
VLANIF10
10.110.1.2/24 Switch C GE1/0/0
VLANIF70
192.168.2.2/24
Quidway S7700 Smart Routing Switch
Configuration Guide - Multicast 9 IPv4 Multicast Routing Management
Issue 01 (2011-07-15) Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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