Symptom
Few minutes after ISSU (bin2upg) is successfully completed in either native or LXC mode there is a complete IPv4 multicast traffic drop. IPv6 multicast traffic is not affected.
Conditions
MAC lookup mode is enabled in the VLANs carrying IPv4 multicast traffic with "layer-2 multicast lookup mac" command. MLD is disabled globally.
Workaround
-Reload the switch after the upgrade process is completed to fully recover from the IPv4 multicast traffic drop.
-Remove the MAC lookup mode prior performing the upgrade process then add it back once the upgrade is completed. In this case a small drop of IPv4 multicast traffic is expected.
-Disable MLD snooping on the VLANs configured with MAC mode.
Further Problem Description
"As part of the ISSU, both IGMP and MLD receives the ?layer-2 multicast lookup mac? configuration, and silently accepts the configuration without setting the MAC mode, because MLD/IGMP hasn’t received the VLAN up notification yet. But when the VLAN up notification is being processed, and since MLD snooping is disabled on the box, MLD sends out disable message with IP as lookup mode, because we haven’t re-processed ?layer-2 multicast …? configuration yet.
Since IGMP snooping is enabled, IGMP process doesn’t send out a message to MFDM right away, and by the time we complete the VLAN up notification processing, IGMP would have re-processed ?layer-2 configuration? and sends out correct message.
Since ?layer-2 multicast lookup mac? is not supported in MLD, and IGMP sends out a right message with right lookup mode, ideally, we should act on the IGMP message and ignore the MLD mode notification."
