Spanning Tree Protocol Flashcards

1
Q

Loop protection

A
  • Connect two switches to each other
    • They’ll send traffic back and forth forever
    • There’s no “counting” mechanism at the MAC layer
  • This is an easy way to bring down a network
    • And somewhat difficult to troubleshoot
    • Relatively easy to resolve

• IEEE standard 802.1D to prevent loops in bridged
(switched) networks (1990)

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2
Q

Switch operation

A

• Forwarding decisions made by MAC address
• Keeps a big table of MAC address that have been
seen
• All forwarding decisions are filtered through this list

• If the destination MAC is unknown, the frame is
flooded
• Sent to every switch port in the local subnet/VLAN
• Hopefully the destination station will respond

  • Flooding is hopefully a temporary process
    • Directed traffic resumes when the MAC is seen
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3
Q

STP port states

A

• Blocking - Not forwarding to prevent a loop
• Listening - Not forwarding and cleaning the MAC
table
• Learning - Not forwarding and adding to the MAC
table
• Forwarding - Data passes through and is fully
operational
• Disabled - Administrator has turned off the port

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4
Q

RSTP (802.1w)

A
  • Rapid Spanning Tree Protocol (802.1w)
    • A much-needed updated of STP
    • This is the latest standard
  • Faster convergence
    • From 30 to 50 seconds to 6 seconds
  • Backwards-compatible with 802.1D STP
    • You can mix both in your network
  • Very similar process
    • An update, not a wholesale change
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