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What is the SNMP OID to fetch the ports assigned to VLANs?

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TitleWhat is the SNMP OID to fetch the ports assigned to VLANs?
Question
What is the SNMP OID to find the ports assigned to VLANs?
Environment
Summit All
Blackdiamond All
EXOS All
Answer
This is a two step process -

Step 1: First, we will need to have the VLAN to OID number tagging information. This can be fetched using the "extremeVlanIfVlanId" OID - 1.3.6.1.4.1.1916.1.2.1.2.1.10
User-added image
In the example provided above, VLAN ID 1 is mapped to 1000004, VLAN ID 4091 is mapped to 1000010 and so on.

Step 2: Once we have this information, we can find the ports mapped to a VLAN as tagged or untagged. This can be fetched using "extremeVlanOpaqueTable" OID - 1.3.6.1.4.1.1916.1.2.6.1
User-added image
In the image above, 1000004 is actually VLAN ID 1 (as mentioned in the first image) and the ".9" or ".1" following it is actually the slot number in case we are fetching information from a SummitStack or a Blackdiamond chassis. Although the above image shows only the untagged ports, similar information is fetched for VLANs present as tagged on the ports as well using the same OID.


 
Additional notes
Interpreting the port mapping information:
  • For example, in "1000004.1" (VLAN ID 1 slot 1), the port numbers are represented by "3F FF FF 00 00" and so on. In order to read this information, we must read the information in binary form.
  • The first four ports (1, 2, 3, 4) in slot 1 is represented by "3" which in Binary is 0011. This essentially means the VLAN ID 1 is not present as untagged on port 1 and 2, but is untagged on ports 3 and 4.
  • The second four ports (5, 6, 7, 8) in slot 1 is represented by "F", which in Binary is 1111. This means the VLAN ID 1 is untagged on ports 5, 6, 7 and 8.
  • Similarly, we can say that the VLAN with ID 1 is untagged on ports 9 -  24 also (represented by FF FF).
  • Information for VLAN ID 1 on slot 9 (1000004.9) can also be read in a similar fashion.

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