STP changing link cost

STP cost long mode

STP cost short mode

STP how to find the root bridge


Port costs for [STP](/spanning-tree-protocol-stp) have been modified to accommodate larger interface speeds.   Originally, they were calculated using the formula 1Gbps/bandwidth using a 16-bit number. This is called [short mode](/stp-cost-short-mode). To accommodate the higher speeds available today and in the future, this has been modified to the use of a 32-bit number with the formula 20 Tbps / bandwidth. This is called [long mode](/stp-cost-long-mode).

You can configure a switch to use either the short or long mode using the `spanning-tree pathcost method` command. 

Most modern switches use the long path cost method by default.

Links:

https://content.cisco.com/chapter.sjs?uri=/searchable/chapter/content/en/us/td/docs/routers/nfvis/switch_command/b-nfvis-switch-command-reference/spanning_tree_commands.html.xml#wp4160553061

https://forum.networklessons.com/t/spanning-tree-cost-calculation/1111/97?u=lagapides

STP Cost Calculation Methods

SDN - what is orchestration

SG300-10 - InterVLAN routing defaults

SNMP - Engine ID

SNMP - Index shuffling

SNMP - Simple Network Management Protocol

SNMP - Version 3 security levels

SNMP - snmp-server community and host commands

SNMP monitoring routing on a Nexus device

SNMP trap vs inform

SNMP walk

SPAN capturing control packets

SPAN multiple destination ports on Cisco IOS device

SPAN using VLANs as a source on a Nexus device

SPAN

SSH - domain-name prerequisite

SSH connectivity - troubleshooting

STP - Aging time reduction with a TCN

STP - BPDU generation and port roles

STP - BPDUGuard, BPDUFilter, and Portfast

STP - BPDUs on a switch where STP is disabled

STP - Disabling spanning-tree

STP - Dispute

STP - Learning State

STP - MST and PVST+ selecting root port

STP - MST maps groups of VLANs

STP - MST region attributes

STP - MST viewed as a single switch by PVST+

STP - Multiple Spanning Tree (MST)

STP - PVST+ and Rapid PVST+ interaction

STP - Per VLAN Spanning Tree plus (PVST+)

STP - RSTP EdgePort

STP - RSTP convergence process

STP - RSTP port roles

STP - RSTP proposal-agreement process

STP - RSTP while timer

STP - Shortest Path Bridging (SPB)

STP - Topology Change Acknowledgement (TCA)

STP - bridge priority

STP - determining the blocked port using port ID

STP - port identification

STP - port roles

STP - port states

STP - what bridge ID does the MST region use

STP - what is a topology change

STP BPDU Filter

STP BPDU Guard

STP BPDU Types

STP BPDU destination MAC address

STP Loop Guard

STP Max Age

STP Message Age

STP PortFast

STP Portfast Options

STP Root Bridge selection

STP Root Guard

STP Topology Change (TC) flag

STP Topology Change Timer

STP UDLD and Autonegotiation

STP UDLD

STP bridge priority values

STP configuring on EtherChannel

STP configuring portfast

STP contents of a BPDU

STP determining blocked port using cost

STP direct vs indirect link failure

STP fine tuning the spanning tree protocol

STP how a switch identifies a BPDU

STP interface type

STP prio nbr value

STP topology change process

Security - 802.1x with WLC and AAA server

Security - Cisco AnyConnect Secure Mobility Client

Security - Cisco Secure Client

Security - Cisco VPN Client

Security - Cisco VPN client software

Security - Diffie-Hellman groups

Security - Extensible Authentication Protocol over LAN (EAPOL)

Security - GETVPN

Security - IEEE 802.1X

Security - IOS Usernames and Passwords

Security - IPsec nonce

Security - Kerberos

Security - MAC Authentication Bypass

Security - Network Access Control (NAC)

Security - Secure Unique Device Identifier (SUDI)

Security - WPA 4-way handshake

Security - WebVPN

Security - accessing VTY from another VRF

Security - assigning privilege levels, syntax and behavior

Security - bogons

Security - broadcast-multicast storm

Security - configuring TACACS from another VRF

Security - privilege levels and command output

STP Cost Calculation Methods

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