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Storage systems connected to a Cisco UCS host cannot connect or ping with jumbo frames enabled on a VLAN tagged interface

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Applies to

  • Data ONTAP 6.4 or later
  • 7-mode and Clustered Data ONTAP.

  The storage system is connected to a Cisco UCS system. The interface has one or more VLANs created and jumbo frames are enabled (MTU 9000).

Issue

Clients will not be able to connect to LUNs or NFS exports on the storage system. Clients may be able to mount exports but other operations against these mounts will fail.

The behavior described in this article can be confirmed using ping tests. The results will be as follows:

  • With the UCS interface configured as an access port and VLANs not configured on the storage system, all traffic operates as expected.
  • With the UCS interface configured as a trunk port and VLAN interfaces configured on the storage system:
    • Use 'ping' to verify that the issue only affects connectivity for jumbo frames.
    • ping -s -v <UCS server IP>
      Press Ctrl-C to stop the ping after a few seconds. This should succeed. If it does not, the connectivity issue is not related to the issue described by this article.
    • ping -s -v <UCS server IP> 1400
      Press Ctrl-C to stop the ping after a few seconds. This should also succeed. This increases the ICMP payload to 1400 bytes. This is still below the default MTU on the UCS. If this does not succeed, the connectivity problem is not related to the issue described by this article.
    • ping -s -v <UCS server IP> 9000
      Press Ctrl-C to stop the ping after a few seconds. If the issue is related to the issue described in this article, the ping should fail. The same command will produce successful pings if the storage system does not have VLANs configured, as described above

 

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