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What are the networking layer 2 reachability requirements in ONTAP 9?

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Applies to

ONTAP 9

Answer

  • To identify OSI layer 2 reachability issues, an L2 algorithm is used to ping the MAC addresses of the other ports in the cluster that belong to the same broadcast domain.
  • The L2 ping is performed by sending Connectivity Fault Management (CFM) frames.
  • A port considers itself 'healthy' if it receives a CFM frame from any other port in its configured broadcast domain.
  • A port considers itself 'degraded' if it is receives no CFM frames from its configured broadcast domain.

Example:

  1. Four ports across two nodes are configured to belong to the storage-side broadcast domain TEST. 
    • node1:e0a
    • node1:e0b
    • node2:e0a 
    • node2:e0b
  2. On the switch side, all 4 ports are expected to be configured on switch-side VLAN 10.
    • Accidentally, one port node2:e0b is configured on switch-side VLAN 20.
  3. The 3 ports on VLAN 10 can L2 ping each other and will be marked as healthy.
    • node1:e0a on VLAN10 sends CFM frames towards the other ports that belong to storage-side broadcast domain TEST. ​​
    • The switch successfully forwards the CFM frames to the ports on VLAN 10.
    • node1:e0a is marked as healthy.
    • The process is repeated for ports node1:e0b and node2:e0a 
  4. Since it is in VLAN 20, port node2:e0b on VLAN 20 will be unable to L2 ping the other 3 ports , so will be marked degraded.
    • node2:e0b on VLAN20 sends CFM frames towards the other ports that belong to storage-side broadcast domain TEST. ​
    • The switch is not configured to forward traffic from VLAN 20 to VLAN 10, so the CFM frames do not read the ports on VLAN 10.
    • node2:e0b is marked as degraded.
  5. In this example, the storage-side configured broadcast domain does not match the switch-side configured broadcast domains.
    • According to the storage-side configuration, the ports are all in a single broadcast domain TEST, and therefore are expected to have L2 reachability.
    • According to the switch-side configuration, the ports are spread across two separate broadcast domains VLAN 10 and VLAN 20, and therefore lack L2 connectivity.
    • Port(s) was marked degraded when ONTAP detected that the storage-side and switch-side broadcast domain configurations do not match.
  6. To check L2 reachability on NetApp, use the network port reachability show command to see if ports in the same broadcast domain can communicate via CFM (Connectivity Fault Management) frames. Look for "no-reachability" status or "degraded" health results which often point to switch/cabling issues or VLAN mismatches.  


::*> broadcast-domain show -broadcast-domain TEST
  (network port broadcast-domain show)
IPspace Broadcast                                         Update
Name    Domain Name    MTU  Port List                     Status Details
------- ----------- ------  ----------------------------- --------------
Default TEST       1500
                            node1:e0a               complete
                            node1:e0b               complete
                            node2:e0a               complete
                            node2:e0b               complete


::> net port show -health
  (network port show)
                          Health
Node       Port      Link Status   Degraded Reasons
--------   --------- ---- -------- -----------------------
node1
           e0a       up   healthy  -
           e0b       up   healthy  -

node2
           e0a       up   healthy  -
           e0b       up   degraded l2_reachability 

Note: node2:e0b is the switch-side VLAN 20 port.

Additional Information

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