S6720交换机堆叠场景下组播业务出现堆叠线路带宽拥塞
问题描述
设备类型为S6720-54C-EI-48S-AC
设备版本为V200R010C00SPC600；补丁为：v200r010sph008
组网拓扑图
故障描述：客户采用二层组播进行业务测试，前期测试组播源分别连接在堆叠主交换机上，接受者分别连接在堆叠主备交换机上，业务测试发现堆叠链路带宽近100%，组播流量出现丢包，按照客户流量堆叠带宽应该不会超过万兆，因此怀疑堆叠机制异常
告警信息
无
处理过程
1、按照客户的测试结果，简化测试过程，将组播源以及接受者均连接在同一台堆叠主交换机
2、查看堆叠线缆是否仍然由组播流量
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===============display interface brief===============
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PHY: Physical
*down: administratively down
#down: LBDT down
(l): loopback
(s): spoofing
(E): E-Trunk down
(b): BFD down
(e): ETHOAM down
(dl): DLDP down
(lb): LBDT block
InUti/OutUti: input utility/output utility
Interface PHY Protocol InUti OutUti inErrors outErrors
Eth-Trunk10 up up 0% 0% 0 0
XGigabitEthernet0/0/41 up up 0% 0% 0 0
XGigabitEthernet0/0/42 up up 0% 0% 0 0
XGigabitEthernet1/0/41 *down down 0% 0% 0 0
XGigabitEthernet1/0/42 *down down 0% 0% 0 0
LoopBack0 up up(s) 0% 0% 0 0
MEth0/0/1 down down 0% 0% 0 0
NULL0 up up(s) 0% 0% 0 0
Vlanif4 up up -- -- 0 0
Vlanif66 down down -- -- 0 0
Vlanif113 up up -- -- 0 0
XGigabitEthernet0/0/1 up up 0% 0% 0 0
XGigabitEthernet0/0/2 up up 0% 0% 0 0
XGigabitEthernet0/0/3 up up 0% 0% 0 0
XGigabitEthernet0/0/4 up up 0% 0% 0 0
XGigabitEthernet0/0/5 up up 0% 0% 0 0
XGigabitEthernet0/0/6 up up 0% 0% 0 0
XGigabitEthernet0/0/7 up up 0% 0% 0 0
XGigabitEthernet0/0/8 up up 0% 0% 0 0
XGigabitEthernet0/0/9 up up 0% 7.28% 0 0
XGigabitEthernet0/0/10 up up 0% 0% 0 0
XGigabitEthernet0/0/11 up up 7.28% 0% 0 0
XGigabitEthernet0/0/12 up up 0% 0% 0 0
XGigabitEthernet0/0/13 up up 0% 0% 0 0
XGigabitEthernet0/0/14 up up 0% 0% 0 0
XGigabitEthernet0/0/15 up up 0% 0% 0 0
XGigabitEthernet0/0/16 up up 0% 0% 0 0
XGigabitEthernet0/0/17 up up 0% 0% 0 0
XGigabitEthernet0/0/18 up up 0% 0% 0 0
XGigabitEthernet0/0/19 up up 0% 0% 0 0
XGigabitEthernet0/0/20 up up 0% 0% 349 0
XGigabitEthernet0/0/21 down down 0% 0% 0 0
XGigabitEthernet0/0/22 down down 0% 0% 0 0
XGigabitEthernet0/0/23 down down 0% 0% 0 0
XGigabitEthernet0/0/24 down down 0% 0% 0 0
XGigabitEthernet0/0/25 up up 0% 0% 0 0
XGigabitEthernet0/0/26 down down 0% 0% 0 0
XGigabitEthernet0/0/27 down down 0% 0% 0 0
XGigabitEthernet0/0/28 down down 0% 0% 0 0
XGigabitEthernet0/0/29 down down 0% 0% 0 0
XGigabitEthernet0/0/30 down down 0% 0% 0 0
XGigabitEthernet0/0/31 down down 0% 0% 0 0
XGigabitEthernet0/0/32 down down 0% 0% 0 0
XGigabitEthernet0/0/33 down down 0% 0% 0 0
XGigabitEthernet0/0/34 down down 0% 0% 0 0
XGigabitEthernet0/0/35 down down 0% 0% 0 0
XGigabitEthernet0/0/36 down down 0% 0% 0 0
XGigabitEthernet0/0/37 down down 0% 0% 2 0
XGigabitEthernet0/0/38 down down 0% 0% 0 0
XGigabitEthernet0/0/39 up up 0% 0% 0 0
XGigabitEthernet0/0/40 down down 0% 0% 0 0
XGigabitEthernet0/0/43 down down 0% 0% 0 0
XGigabitEthernet0/0/44 down down 0% 0% 0 0
XGigabitEthernet0/0/45 down down 0% 0% 0 0
XGigabitEthernet0/0/46 down down 0% 0% 0 0
XGigabitEthernet0/0/47 up up 0% 7.41% 0 0
XGigabitEthernet0/0/48 up up 0% 7.41% 0 0
XGigabitEthernet1/0/1 *down down 0% 0% 0 0
XGigabitEthernet1/0/2 *down down 0% 0% 0 0
XGigabitEthernet1/0/3 *down down 0% 0% 0 0
XGigabitEthernet1/0/4 *down down 0% 0% 0 0
XGigabitEthernet1/0/5 *down down 0% 0% 0 0
XGigabitEthernet1/0/6 *down down 0% 0% 0 0
XGigabitEthernet1/0/7 *down down 0% 0% 0 0
XGigabitEthernet1/0/8 *down down 0% 0% 0 0
XGigabitEthernet1/0/9 *down down 0% 0% 0 0
XGigabitEthernet1/0/10 *down down 0% 0% 0 0
XGigabitEthernet1/0/11 *down down 0% 0% 0 0
XGigabitEthernet1/0/12 *down down 0% 0% 0 0
XGigabitEthernet1/0/13 *down down 0% 0% 0 0
XGigabitEthernet1/0/14 *down down 0% 0% 0 0
XGigabitEthernet1/0/15 *down down 0% 0% 0 0
XGigabitEthernet1/0/16 *down down 0% 0% 0 0
XGigabitEthernet1/0/17 *down down 0% 0% 0 0
XGigabitEthernet1/0/18 *down down 0% 0% 0 0
XGigabitEthernet1/0/19 *down down 0% 0% 0 0
XGigabitEthernet1/0/20 *down down 0% 0% 0 0
XGigabitEthernet1/0/21 *down down 0% 0% 0 0
XGigabitEthernet1/0/22 *down down 0% 0% 0 0
XGigabitEthernet1/0/23 *down down 0% 0% 0 0
XGigabitEthernet1/0/24 *down down 0% 0% 0 0
XGigabitEthernet1/0/25 *down down 0% 0% 0 0
XGigabitEthernet1/0/26 *down down 0% 0% 0 0
XGigabitEthernet1/0/27 *down down 0% 0% 0 0
XGigabitEthernet1/0/28 *down down 0% 0% 0 0
XGigabitEthernet1/0/29 *down down 0% 0% 0 0
XGigabitEthernet1/0/30 *down down 0% 0% 0 0
XGigabitEthernet1/0/31 *down down 0% 0% 0 0
XGigabitEthernet1/0/32 *down down 0% 0% 0 0
XGigabitEthernet1/0/33 *down down 0% 0% 0 0
XGigabitEthernet1/0/34 *down down 0% 0% 0 0
XGigabitEthernet1/0/35 *down down 0% 0% 0 0
XGigabitEthernet1/0/36 *down down 0% 0% 0 0
XGigabitEthernet1/0/37 *down down 0% 0% 0 0
XGigabitEthernet1/0/38 *down down 0% 0% 0 0
XGigabitEthernet1/0/39 *down down 0% 0% 0 0
XGigabitEthernet1/0/40 *down down 0% 0% 0 0
XGigabitEthernet1/0/43 *down down 0% 0% 0 0
XGigabitEthernet1/0/44 *down down 0% 0% 0 0
XGigabitEthernet1/0/45 down down 0% 0% 0 0
XGigabitEthernet1/0/46 down down 0% 0% 0 0
XGigabitEthernet1/0/47 up up 7.41% 0% 0 0
XGigabitEthernet1/0/48 up up 7.41% 0% 0 0
40GE0/0/1 down down 0% 0% 0 0
40GE0/0/2 down down 0% 0% 0 0
40GE1/0/1 down down 0% 0% 0 0
40GE1/0/2 down down 0% 0% 0 0
从端口带宽确认，堆叠端口XGigabitEthernet0/0/47、XGigabitEthernet0/0/48以及XGigabitEthernet1/0/47、XGigabitEthernet1/0/48均有流量；
3、确认堆叠端口流量是单播、广播还是组播，查询堆叠端口，确认该堆叠端口下为组播流量
4、是否为未知组播转为广播，配置丢弃未知组播
vlan 4
multicast drop-unknown
igmp-snooping enable
igmp-snooping version 3
查看堆叠端口带宽仍然有组播流量
5、再次与研发确认堆叠交换机组播流量转发机制，确认问题根因
根因
盒式交换机堆叠对于二层组播报文的转发，默认是将堆叠链路作为出接口，即二层组播报文的转发一定会有组播流量经过堆叠业务口进行转发；
该种机制主要解决如下问题
1、在出现链型堆叠的场景下，如A、B、C三台交换机组成链型堆叠，如果有A交换机与C交换机组播流量交互，需要将A、B、C交换机的堆叠链路作为转发出接口；
2、由于堆叠端口已经作为出接口，可以加速转发效率
解决方案
建议客户增加堆叠链路，以解决组播流量过大导致丢包
建议与总结
堆叠交换机在进行组播流量转发的情况下，堆叠端口会有组播流量占用带宽，因此在进行堆叠交换机规划时，要考虑组播流量，如果组播流量过大，超过堆叠带宽，建议增加堆叠链路
