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CONTAP-796778: Disabling CDP switchside can cause data access issues

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Issue

  • In a switched ONTAP cluster where both node's cluster LIFs are attached to Ethernet  switches, CDP or LLDP gets manually disabled switch side by an admin, for example in Cisco NX-OS using command: no cdp enable
  • ONTAP Cluster Session Manager (CSM) relies on CDP/LLDP on its Cluster ipspace ports to be able to negotiate optimized switch fabric paths cross-node.
  • Without CDP/LLDP available, CSM flips to switchless-mode and tries to mitigate the situation using TCP-fallback (from RDMA). Event log shows a sequence like:

    Fri Mar 13 13:37:14 +0200 [MyCluster01-01: mgwd: cluster.network.config:notice]: The cluster network configuration transitioned to switchless.
    Fri Mar 13 13:37:39 +0200 [Mycluster01-01: vifmgr: vifmgr.clntdev.updated:notice]: Remote device MyClusterSwitch(xxxxxxxxxxx) (model: -, version: -, IP address: -) has been detected on the network.
    Fri Mar 13 13:38:33 +0200 [MyCluster01-01: server_common_RPC: csm.ctFallbackSwitchless:notice]: Cluster Session Manager (CSM) could not determine the cluster ports that are directly connected between the switchless cluster nodes to create the RDMA connections for session "1a0653d652191c1a". CSM will use TCP connections as defaults.

  • ONTAP cross-node NVMeOF CLIENT connections fail and NAS/SAN connections from clients can become temporarily unavailable unless CDP/LLDP gets re-enabled switch-side:

    Fri Jun 19 13:40:51 +0200 [Mycluster01-02: CsmMpAgentThread: nvmf.remote.status.cb:notice]: NVMeOF remote status callback endpoint=CLIENT, status=Session Failed.
    Fri Jun 19 13:40:52 +0200 [Mycluster01-02: kernel: Nblade.noCsmSession:notice]: params: {'bladeId': 'xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx'}

  • After CDP/LLDP got manually re-enabled switch side, client data access to ONTAP recovers automatically along with events similar to:

     
    Fri Jun 19 14:05:34 +0200 [Mycluster01-02: vifmgr: vifmgr.clntdev.updated:notice]: Remote device MyClusterSwitch(xxxxxxxxxxx) (model: OTHER, version: Cisco Nexus Operating System (NX-OS) Software, Version 10.4(5), IP address: 10.1.3.37) has been detected on the cluster network.
    Fri Jun 19 14:05:44 +0200 [Mycluster01-01: CsmMpAgentThread: nvmf.remote.status.cb:notice]: NVMeOF remote status callback endpoint=CLIENT, status=Session OK.

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