Networking

VLAN routing (netgear) with vlan setup as per netgear instructions and Untagged ports on port 23 and 24 of GS728TP, also needed to setup:

On desktop

sudo route add -net <vlan>.0.0 netmask 255.255.0.0 gw <gs728TP ip> metric 100

where vlan is the ip parts set in vlan setup of smart switch.

On device connected to smart switch port 23.

route add -net <desktop>.0 netmask 255.255.255.0 gw <vlan>.0.1

where desktop is the ip parts of the desktop nic the switch is connected to.

resulting routes were

Desktop (ip forwarding is enabled)

Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
....
<vlan>.0.0 <gs728TP ip> 255.255.0.0 UG 100 0 0 eth1
link-local * 255.255.0.0 U 1000 0 0 eth1
<nic>.0 * 255.255.255.0 U 100 0 0 eth1

Device

Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface
127.0.0.0 * 255.0.0.0 U 0 0 0 lo
<vlan>.0.0 * 255.255.0.0 U 100 0 0 eth0
<desktop>.0 <vlan>.0.1 255.255.255.0 UG 0 0 0 eth0

Pinging a loopbacked set of NICs

You need to test the ethernet hardware without a switch. Loop two nics and use ping6 ping6 -f -q -c 500 -w 2 -L -r ff02::1%eth1 Adjust count and wait parameters as needed.