One of the features that attracted me to try LibreNMS was the potential to generate a network map and see the inter-connectivity of devices as detected by LLDP…
While all our core switches support LLDP a few of our older edge switches don’t so unfortunately our network map is incomplete however I’ve noticed another issue, and I’m not sure if this is a bug or just expected behaviour.
And that is that LibreNMS doesn’t seem to publish LLDP retrieved remote port data unless the LLDP device at the other end can also have LLDP data queried by SNMP ?
For example if I have two switches connected together, both support LLDP and both support LLDP data being queried through SNMP, I see them linked in the network map, in the neighbour lists of the switches, and also on the last (unlabelled) column of the port lists for the switches. This is extremely handy.
However we have 52 Meraki MR42 access points which also fully support LLDP - the Meraki web interface for the AP will report the name and port of the switch the AP is connected to and the web interface of the switch under LLDP remote port table will report the name and details of the access point. So they are definitely exchanging LLDP data with each other. (It is also used for POE negotiation)
Unfortunately if I look at the port list or neighbour list of the switch in LibreNMS there is nothing shown for the access point.
The access point is being queried by SNMP as well however I’m fairly sure that the access point does not make LLDP information available via SNMP - at least it doesn’t show a Neighbours tab in LibreNMS. (It does return port traffic statistics though)
So the question is, if only ONE end of an LLDP link can report LLDP data via SNMP, should that data be displayed in LibreNMS ?
Here is an example from the web interface of a D-Link DGS-1210-28P under LLDP remote port table:
Port ID : 1 --------------------------------------------------------------------------- Remote Entities Count : 1 Entity 1 Chassis ID Subtype : MAC Address Chassis ID : AC-17-C8-05-20-D6 Port ID Subtype : Interface Alias Port ID : 0 Port Description : eth0 System Name : IT Dept System Description : Meraki MR42 Cloud Managed AP System Capabilities : WLAN Access Point Management Address Count : 0 (NONE) Port PVID : 0 PPVID Entries Count : 0 (NONE) VLAN Name Entries Count : 0 (NONE) Protocol Identity Entries Count : 0 (NONE) MAC/PHY Configuration/Status : (NONE) Power Via MDI : (NONE) Link Aggregation : (NONE) Maximum Frame Size : (NONE) Unknown TLVs Count : 0 (NONE)
So the switch is providing LLDP data for the access point. However this doesn’t show up for port 1 on the switch on LibreNMS, nor in the neighbours list. Two other switches which are connected to this switch do show LLDP data in neighbours and in the port list.
I appreciate that not being able to poll LLDP data directly from both ends of a link may not be enough information to positively link two nodes together in a network map, however having the name and some details of a remote device as reported by LLDP listed against the port in a port list on a switch is still extremely useful information especially if the device at the other end of the link is a BYO device or something which doesn’t support SNMP.
Thoughts on whether this is a bug or expected ?