Distributed Switching

Traditional L2 / L3 Network

• Some links that are good and some links that are in their blocking state.

• Create STP on the left and STP on the right.

• Distributed Chasis Link Aggregation

  • Making two separate switches participating as a team
  • Pair all the links together and support each other with high availability

• Distribution switches

  • More powerful
    • The ability to scale our forwarding plan
  • Perform routing
  • Enforce ACL/security policy
  • QoS
  • Aggregate link between
    • Downstream switches think is the same exact device on both wires

• Access layer switches

  • Connect to access points, printers, etc
  • Connect client devices to network

• Issues

  • Need to block at L2 on redundant links

Distribution Switching

• Behave as a cluster

• What is happening down at the Access Layer

  • Historically you used path 1 or path 2
  • Circles make you think of List Aggregation
    • LACP to forward all your traffic
      • Can recover from a problem really really fast, it is faster than STP
      • All your calculations are based on a port channel interface
      • If one of the physical links disappear it just lowers its bandwith but it is still up.
  • We are going from an access switches to two different core switches
    • We know we can get to one of the cores with one path that is faster than the other so you block the other path.
  • Same Bridge ID from both switches

• When we perform a reboot, it might be down for about 7 minutes

  • ACL switch sees the link up
  • STP doesn't have to change, OSPF does not have to change.