I've been looking at the current state of the vlan plugin to ipdevpoll, but it was quite unfinished and I decided to write something from scratch.
I'm writing a plugin based solely on BRIDGE-MIB and Q-BRIDGE-MIB. Since Cisco has poor or no support for the latter, I'll later be writing a plugin to collect VLAN information from Cisco proprietary MIBs.
My question is:
Setting the vlan value of an interface record (previously swport) usually means the "configured" VLAN of that port. But there are possibly two ways to collect this from the Q-BRIDGE-MIB, and they have subtly different meanings.
The options are basically ingress and egress VLANs. Q-BRIDGE holds a table of ports [1] with a VLAN (PVID) value for each. This is the VLAN assigned to any untagged ethernet frame coming in on that port.
Then there is a table of active VLANs [2], each with a column listing egress ports that will send tagged or untagged frames from this VLAN.
Which one should we choose? Should we look at both and do some sort of magic if they differ?
[1] http://tools.cisco.com/Support/SNMP/do/BrowseOID.do?local=en&translate=T... [2] http://tools.cisco.com/Support/SNMP/do/BrowseOID.do?local=en&translate=T...
Morten Brekkevold wrote:
I've been looking at the current state of the vlan plugin to ipdevpoll, but it was quite unfinished and I decided to write something from scratch.
I'm writing a plugin based solely on BRIDGE-MIB and Q-BRIDGE-MIB. Since Cisco has poor or no support for the latter, I'll later be writing a plugin to collect VLAN information from Cisco proprietary MIBs.
My question is:
Setting the vlan value of an interface record (previously swport) usually means the "configured" VLAN of that port. But there are possibly two ways to collect this from the Q-BRIDGE-MIB, and they have subtly different meanings.
The options are basically ingress and egress VLANs. Q-BRIDGE holds a table of ports [1] with a VLAN (PVID) value for each. This is the VLAN assigned to any untagged ethernet frame coming in on that port.
Then there is a table of active VLANs [2], each with a column listing egress ports that will send tagged or untagged frames from this VLAN.
Which one should we choose? Should we look at both and do some sort of magic if they differ?
In real life I do not know of any cases where it is configurable on a switch to set a specific ingress or egress vlan value on a switchport and thus potentially let them differ.
My suggestion is to follow the ingress vlan value for now and let deployments/pilots decide if there are corner cases we do not see at the moment.
[1] http://tools.cisco.com/Support/SNMP/do/BrowseOID.do?local=en&translate=T... [2] http://tools.cisco.com/Support/SNMP/do/BrowseOID.do?local=en&translate=T...
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