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Multicast Traffic Fails to Be Forwarded on an S5700

Publication Date:  2019-07-17 Views:  90 Downloads:  0

Issue Description

Topology: A large number of blade servers are connected to two switch modules on E9000 chassis. These blade servers are both multicast receivers and multicast sources.

 

Symptom: After PIM-DM and IGMP are enabled on VLANIF interfaces of the core switch, multicast traffic in the same VLAN can be transmitted normally, but multicast traffic across different VLANs fails to be transmitted.

Handling Process

Check the IGMP and PIM configurations on interfaces. It is found that PIM and IGMP are both enabled on VLANIF interfaces.

Check (*,G) entries on the switch. The (*,G) entries are normal.

Obtain multicast packets. The obtained packets show that the initial TTL value of multicast packets sent by the client is 1. As a result, Layer 3 multicast traffic fails to be forwarded.

 

Root Cause

The initial TTL value of multicast packets sent by the client is 1 and becomes 0 when packets reach the next hop. As a result, Layer 3 multicast traffic fails to be forwarded.

[switch-acl-3000]rule 5 permit ip destination 225.1.1.11 0

[switch]capture-packet interface GigabitEthernet 0/0/1 acl 3100 destination terminal packet-num 10

Packet: 1

-------------------------------------------------------

01 00 5e 01 01 28 f0 1f af 27 5d fe 81 00 00 c8

08 00 45 00 00 7c 03 c5 00 00 01 11 a3 72 c0 01

6b 0f e6 01 01 28 15 be 92 11 00 68 18 59 00 00

00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 b1

-------------------------------------------------------

Solution

Change the TTL value of multicast packets to 64. After the configuration is complete, Layer 3 multicast traffic is forwarded normally. The obtained packets show that the TTL value of packets received on the switch is 63.

 

END