Involved Products and Versions

All versions of modular switches

Networking

In Figure 1-1, ME60-1 and ME60-2 are connected to the Switch through Eth-Trunk3 and Eth-Trunk2 respectively. Multicast subinterfaces of ME60-1 and ME60-2 are Eth-Trunk3.50 and Eth-Trunk2.50 respectively, and PIM is configured on ME60-1 and ME60-2.

Figure 1-1 Networking diagram

Symptom

Both ME60-1 and ME60-2 are DRs, and PIM DR election fails. ME60-1 and ME60-2 forward multicast traffic to the switch separately.

Cause Analysis

Eth-Trunk3 member interface XGE10/0/1 of the Switch has the multicast-suppression packets 0 command configuration. This configuration enables XGE10/0/1 to discard PIM packets.

Procedure

                          Step 1     Run the display pim interface command on ME60-1 and ME60-2 to view PIM information on interfaces. The command output shows that DR priorities of both ME60-1 and ME60-2 are 1 and their DR addresses are local. This indicates that the Switch does not forward PIM packets normally.

<ME60-1> display pim interface Eth-Trunk 3.50
VPN-Instance: public net
Interface     State NbrCnt HelloInt DR-Pri DR-Address
Eth-Trunk3.50 up    0      30       1      10.194.163.17 (local)

<ME60-2> display pim interface Eth-Trunk 2.50
VPN-Instance: public net
Interface     State NbrCnt HelloInt DR-Pri DR-Address
Eth-Trunk2.50 up    1      30       1      10.194.163.18 (local)

                          Step 2     On the Switch, collect traffic statistics of Eth-Trunk2 and Eth-Trunk3, and then run the display traffic policy statistics interface interface-type interface-number inbound command to view the traffic volume. The command output shows that the Switch receives PIM Hello packet of ME60-2 but does not forward the packet through Eth-Trunk3.

#
acl number 3000
 rule 5 permit ip destination 224.0.0.13 0
#
traffic classifier test
 if-match acl 3000
#
traffic behavior test
 statistic enable
#
traffic policy test
 classifier test behavior test
#
interface Eth-Trunk2
 traffic-policy test inbound 
 traffic-policy test outbound 
#
interface Eth-Trunk3
 traffic-policy test inbound 
 traffic-policy test outbound

                          Step 3     Check the configuration of Eth-Trunk3 on the Switch, finding that Eth-Trunk3 member interface XGE10/0/1 has the multicast-suppression packets 0 command configuration. This configuration enables XGE10/0/1 to discard PIM packets. After this command configuration is deleted, this problem is solved.

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