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Discovery Task Stops When Encountering VLAN Not Assigned to Any Ports

IP Fabric version: all

Known affected platforms: Arista EOS, platform 7280sr3, version 4.26.4M

Description: The show spanning-tree vlan detail command stops when it encounters a VLAN configured on the device but not assigned to any ports (except for the default VLAN 1). This issue has been observed when running rapid-PVST spanning tree but could potentially affect other versions.


arista#show vlan
VLAN  Name                             Status    Ports
----- -------------------------------- --------- -------------------------------
1     default                          active
2     BAD_VLAN                         active
5     GOOD_VLAN                        active    Et1, Et2
arista#sho span vlan det
Spanning tree instance for vlan 1
 VL1 is executing the rapid-pvst Spanning Tree protocol
  Bridge Identifier has priority 4096, sysid 1, address 0000.0000.0000
  Configured hello time 2.000, max age 20, forward delay 15, transmit hold-count 6
  We are the root of the spanning tree

No spanning tree information available for vlan 2

Result: Incomplete IP Fabric path lookups.

Temporary fix: Remove the unused VLAN from the configuration using the no vlan # command.

Permanent fix: Unknown. Waiting for a response from Arista.

Wrong End-to-End Path Lookups Due to EOS Bug Assigning Same STP ID to Different Interfaces

IP Fabric version: all

Known affected platforms: Arista DCS-7504N 4.28.6M-30705735.4286M, DCS-7280SR-48C6-F 4.26.4M-25280047.4264M

Description: Arista is assigning the same STP ID to different ports. For spanning tree port IDs to serve their purpose, they need to be unique within an L2 domain. Under certain circumstances (such as when a device’s operational requirements exceed its maximum scalability limits or due to a bug in the device’s operating system), a device may assign the same spanning tree port ID to multiple ports within a single L2 domain. This situation was observed, for example, on Arista DCS-7504N running a software image with internal build version 4.28.6M-30705735.4286M. In IP Fabric, this has resulted in incorrect STP topology calculations and consequent issues in path lookup.

Result: Incomplete path lookups in IP Fabric.

Temporary fix: None.

IP Fabric fix version: To be specified.