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A failure may occur when forming a Multi-Chassis Link Aggregation (MLAG) master/standby connection in configurations where an intermediate switch is used to connect the M-series switches mgmt0 ports. The M-series MLAG configuration requires MDNS packet exchanges over the mgmt0 ports for purposes of "heartbeat" and status communications in addition to Standard Boot Order (IPL) communications. When the mgmt0 MDNS information fails to be exchanged, the two M-series switches display as master/master or master/unknown; although the switch configuration for MLAG and MLAG-VIP are correct, and the mgmt0 ports are able to ping to each other.A constant heartbeat exchange is required through the mgmt0 ports of two switches to establish a MLAG-VIP master/standby connection. The switches in MLAG constantly exchange MDNS packets, i.e., multicast traffic sent to multicast address 224.0.0.251. However, if the intermediate switch connecting the M-series mgmt0 ports does not permit this multicast IP address to be forwarded, MLAG cannot resolve the master/standby roles. See the example below:
HPE M-Series ONYX switches in an MLAG configuration are affected by this advisory:HPE SN2100M 100GbE 16QSFP28 Half Width Switch (Q2F23A)HPE SN2100M 100GbE 8QSFP28 Half Width Switch (Q2F24A)HPE SN2100M 100GbE 16QSFP28 Power to Connector Airflow Half TAA-compliant (R0P75A)HPE SN2100M 100GbE 16QSFP28 Connector to Power Airflow Half TAA-compliant (R0P76A)HPE SN2010M 25GbE 18SFP28 4QSFP28 Switch (Q9E63A)HPE SN2010M 25GbE 18SFP28 4QSFP28 Power to Connector Airflow TAA-compliant (R0P77A)HPE SN2010M 25GbE 18SFP28 4QSFP28 Connector to Power Airflow TAA-compliant (R0P78A)HPE SN2700M 100GbE 32QSFP28 Switch (Q2F21A)HPE SN2700M 100GbE 32QSFP28 Power to Connector Airflow TAA-compliant (R0P71A)HPE SN2700M 100GbE 32QSFP28 Connector to Power Airflow TAA-compliant (R0P72A)HPE SN2700M 100GbE 16QSFP28 Switch (Q6M26A)HPE SN2410M 25GbE 48SFP28 8QSFP28 Switch (Q2F22A)HPE SN2410M 25GbE 48SFP28 8QSFP28 Power to Connector Airflow TAA-compliant (R0P73A)HPE SN2410M 25GbE 48SFP28 8QSFP28 Connector to Power Airflow TAA-compliant (R0P74A)HPE SN2410bM 10GbE 48SFP+ 8QSFP28 Switch (Q6M28A)HPE SN2410M 25GbE 24SFP28 4QSFP28 Switch (Q6M27A)HPE SN2410bM 10GbE 24SFP+ 4QSFP28 Switch (Q6M29A)HPE SN3700cM 100GbE 32QSFP28 Power to Connector (P2C) Airflow Switch (R3B14A)HPE SN4600cM 100GbE 64QSFP28 Power to Connector (P2C) Airflow Switch (R6R24A)HPE SN3700M 200GbE 32QSFP28 Power to Connector (P2C) Airflow Switch (R5Z74A)
The intermediate switch or device to which themgmt0ports of M-series switches in an MLAG configuration are connected must allow 224.0.0.251 (MDNS protocol) through the intermediate switch regardless of any multicast protocols that are running (igmp, igmp-snooping, etc.)Contact the device vendor to address this issue. If assistance is needed to analyze the TCP dump outputs from thetcpdumpcommands, contact your local countryHPE Customer Supportor log a case via theHPE Support Center.To debug this issue, thetcpdumpcommand may be used. The following command must be run on each switch simultaneously:tcpdump vrf mgmt -i mgmt0 host 224.0.0.251 and (host <IP addr of mgmt0 on switch A> or host <IP addr of mgmt0 on switch B>) -c 200Example:tcpdump vrf mgmt -i mgmt0 host 224.0.0.251 and (host 172.25.140.26 or host 172.25.140.27) -c 200The output of these twotcpdumpcommands should show whether MDNS is being sent or received properly between the twomgmt0interfaces. This output can also be provided to HPE Support to be analyzed.When MDNS packets are being exchanged properly, theshow mlag-vipcommand displays the workingmlag-vip master/standbyrelationship:Document VersionRelease DateDetails3October 13, 2025Instructions to debug the issue in the Resolution section were edited.2April 4, 2024Added "ONYX" to the Title and revised the Affected Products list to include HPE Storage Switch M-series SN4600M.1April 3, 2024Original Document Release.
Operating Systems Affected:Not Applicable
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