STP BPDU  (Bridge Protocol Data Unit) every 2 seconds
EIGRP hello packet ___ seconds above T1, ___ seconds T1 or lower
OSPF hello ____ seconds (ethernet and point-to-point);      ____ second (serial and non-point-to-point)
RIP update every 30 seconds; why not exact 30 seconds?

Layer 3 priority: 255 highest; 1 default; 0 not elected; IP address higher is better
STP root priority: 1 highest; 32768 default; increment 4096; 65536 lowest; MAC address lower is better
STP port priority: 0 highest; 128 default; 240 lowest
 
root port: one per switch -- the one towards (out to) root bridge
designated port: one per segment, receives (inbound) and forwards frames to root port (toward root bridge)
non-designated port: blocked (can be reactivated by STP when network situation changes)
disabled port: administratively shut down (not in the STP game at all)

802.1d  STP (Spanning Tree Protocol)
802.1w RSTP (rapid STP)

802.1q IEEE trunking
802.1p ToS, CoS, QoS  [type of service, class of service, quality of service)
802.1s MST (Multiple Spanning Tree Protocol)

802.3 Ethernet
802.3 u,z,ab,ae (http://en.wikipedia.org/wiki/IEEE_802.3)
802.5 Token ring
802.11abgn (chap 7)







































	      hello		dead
EIGRP: 5/60		15/180 
OSPF: 10/30		40/120