spanning tree algorithm (STA)

Definition of spanning tree algorithm (STA) in The Network Encyclopedia.

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What is STA (spanning tree algorithm)?

An algorithm implemented on bridges and some Ethernet switches that detects redundant paths in an Ethernet network and prevents traffic from endlessly looping around the network. The spanning tree algorithm (STA) allows redundant paths to be used for backup links between bridged networks to provide fault tolerance in an internetwork.


Implementing the STA on Ethernet switches can sometimes prevent clients from renewing their Dynamic Host Configuration Protocol (DHCP) lease with a DHCP server. It might take 10 or 15 seconds for the STA to check the ports on the switch for loops, and if a computer running Microsoft Windows tries to obtain a DHCP lease during this time interval, the DHCPREQUEST packet is lost. You can work around this by disabling the STA on the switch or manually releasing and renewing the computer’s IP address using ipconfig (on Windows NT and Windows 2000) or winipcfg (on Windows 95 and Windows 98).