Generations of Netgear switches and interface names / 2022-05-12

2022-05-12 Generations of Netgear switches and interface names
In my time at Utrecht University computer science I wrote a script to search Cisco switches for a given ethernet address and respond with the port. This could be used to trace things on the network, which helped on incidents in progress.

This script was based on the typical things Cisco switches do with vlan CAM table lookups and the best implementation. CAM stands for Content Addressable Memory: memory optimized for doing lookups by certain content. In the case of a network switch a 6-byte MAC address plus 2-byte vlan id will be used to do a lookup of the 2-byte interface number where it was last seen, and this lookup is done in hardware.

This CAM table is accessible via SNMP, and the funny part is the MAC address for the lookup is also encoded as SNMP identifier. I could get the whole CAM table via snmpwalk but as I only want to lookup 1 MAC address it is way faster to go directly from MAC address to interface number. After that the interface number is translated to an interface name and that name is usually something recognizable to a network engineer.

When I started using managed switches at home from Netgear I adapted the script at home and enhanced it for Netgear switches.

I recently added a third netgear switch when upgrading the fiber to the shed and I updated the script to learn about the new switch.

I noticed the interface names are quite different over the generations of netgear switches.

The oldest switch is a Netgear GSM7224. The interface name from a query is "Unit: 1 Slot: 0 Port: 15 Gigabit - Level".

The second switch is a Netgear GS716Tv2. The interface name from a query is "Slot: 0 Port: 11 Gigabit - Level".

The newest switch is a Netgear GS310TP. The interface name from a query is "GigabitEthernet9".

The Unit: 1 in the GSM7224 suggests some option for stacking multiple switches, but I can't find any mention of that option in the on-line documentation.

The other fun part I notice is interface names never showing the fact that they are actually an SFP interface with an SFP in them. The port status for a port with an SFP is not different from the status for a copper cable at gigabit.

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