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Scan network for vlan info.....how to

Our network has grown, and through the year vlan standards have not always been consistent/followed. At our disposal are the standard tools (snmp, port scans, etc) and Ridgeline v4 and Epicenter.

Are there any tools any one knows of that can scan our network and query each sw for a list of vlans? We are talking over 10000+ switch (XOS, Extremeware, and 24/48si's)....so manually just wont work. I looked for a good length of time, unable to find a resolution online. I am not a SNMP guy (though we have one at work)...but I would also think that each sw could be queried this way as a last resort.


7 replies

Use SNMP. Just figure out the mibs.
Userlevel 5
I once wrote a little script that snmp-scans my Extreme XOS switches (mostly to get a table displaying "port...vlantagged vlanuntagged" because nothing does that out of the box), and used these OIDs:

"vname" => ".", //extremeVlanIfDescr.vlan_no = string NOT the tag, though
"vport" => ".", //extremePortVlanInfoDescr.port.vlan_no = string
"vtag" => ".", //extremeVlanIfVlanId.vlan_no = integer
"tagged" => ".", //extremeVlanOpaqueTaggedPorts .VLANid.SLOT = Hex-String
"untagged" => "." //extremeVlanOpaqueUntaggedPorts .VLANid.SLOT = Hex-String[/code]
Starting at "port" number 1000001 it actually lists pseudo-ports with vlan names and vlan descriptions (and Virtual Routers)

That might get you started - good luck!
Thank you both, will look into it 🙂 Think we will pursue first avenue.
Userlevel 5
Jimmy, I just wanted to add that NetSight has an SNMP browser in which you can customize a FlexView to add the OIDs needed to perform SNMP GETs against. NetSight is our NMS succeeding Ridgeline. A evaluation license is always available if interested.
Userlevel 6
Jimmy, if you try the NetSight route... v6.3 can display graphically the vlans present in the switches in a map.

Granted, this won't work for 10,000s of switches, but I imagine that you are planning on dividing the task in smaller chunks...

Here's a smalll example...

Map and VLAN list (no vlan checked)

VLAN 1 checked. Notice the yellow tag and box in the switches that have VLAN 1 configured.

Same thing but for VLAN 4003.

This would give you a quick visual indication of what is configured where.

As Taykin said, you can download NetSight from the extranet and request a demo license to see if it fits your needs.
Userlevel 6
I forgot to mention that you can dig deeper into each of the devices and see the ports configured for each vlan...

Netdot can scan your network and report on VLANs, it'll even show which switches are configured with different VLANs on trunk ports.