vty stands for Virtual Teletype. What is Teletype?
teletype, or teleprinter, is a device used for communicating text over telegraph lines, public switched telephone network, Telex, radio, or satellite links. Wikipedia explanation of teletype
This means vty is essentially like a virtual computer screen plugged into the router that we can remotely access.
Both SSH and Telnet use this virtual monitor to let you see the router/switch.
line vty 0 4
Configures 5 of these virtual teletypes (vty’s) for us to use. Can think of it having 5 monitors connected to the router. When you SSH to it, you are claiming one of these monitors. Cisco devices support up to a maximum of 16. 0-15
The following is some basic info on STP and RSTP. This list is not comprehensive. Refer to the link at the bottom of the page for more in depth details.
Default Priority is 32768 + VLAN ID
For example, if we are using vlan 10, then our default priority is 32768 + 10 = 32778
RSTP Priority can be set from 0 – 61440 in increments of 4096.
RSTP Port Roles
Ports can fill 1 of 4 roles.
Port Role Description Root Port Port closest to the Root Bridge (Switches going to the Root switch) Designated Port Ports going away from the Root Bridge (To clients) Alternate Port A “backup” port for the Root port. If the Root Port fails, this port takes over Backup Port Essentially a backup port for the designated port RSTP Port Roles RSTP Port States
A port can be in one of 3 states. Well technically 4 states if you include down/unplugged.
Port State Description Discarding Port discards packets (Alternate and Backup Ports) Learning Port learns MACs and doesn’t forward data Forwarding Port forwards data and learns MACs RSTP Port States
RSTP Port Types
There are 3 port Types. Not to be confused with port States or Roles.
Port Type Description Point to Point Switch to Switch Point to Point Edge Edge of Network. Connected to a PC, Printer etc. Shared Half Duplex, Port connected to a Hub STP/RSTP Port Types RSTP Timers
There are three RSTP timers. STP has the same timers, but the MaxAge is 10 seconds, and the Forward Delay is used for both Learning and Listening states which takes a total of 30 seconds to complete.
Timer Name Default Value Description Hello Timer 2 Seconds Time between Hellos created by Root MaxAge 6 Seconds (Hello Timer * 3) How long a Switch should wait before trying to readjust the network Forward Delay 15 Seconds Delay used for Learning/Listening in STP. Shouldn’t be necessary if legacy bridges are not used. RSTP/STP Timers Port Cost
There are technically two types of cost. The newer cost values were introduced so we could use faster ethernet speeds.
By default Cisco switches use the old cost values, but they can be changed to use the new ones.
spanning-tree pathcost method long
Ethernet Speed Old Cost New Cost 10 Mbps 100 2,000,000 100 Mbps 19 200,000 1 Gbps 4 20,000 10 Gbps 2 2000 100 Gbps N/A 200 1 Tbps N/A 20 STP/RSTP Path Cost
More information can be found at the following link.