Indicates the device's functional capabilities as reported in the
most recent CDP message. Possible values are:
R - layer 3 router
T - a layer 2 transparent bridge
B - a layer 2 source-root bridge
S - a layer 2 switch (non-spanning tree)
r - a layer 3 (non routing) host
I - does not forward IGMP Packets to non-routers
H - a layer 1 repeater
A zero-length string indicates no Capabilities field (TLV) was
reported in the most recent CDP message.