1 / 14

Loop Avoidance

Loop Avoidance. Redundant topology eliminates single points of failure. Redundant topology causes broadcast storms, multiple frame copies, and MAC address table instability problems. Broadcast Storms. Host X sends a broadcast. Switches continue to propagate broadcast traffic over and over.

sereno
Download Presentation

Loop Avoidance

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Loop Avoidance • Redundant topology eliminates single points of failure. • Redundant topology causes broadcast storms, multiple frame copies, and MAC address table instability problems.

  2. Broadcast Storms • Host X sends a broadcast. • Switches continue to propagate broadcast traffic over and over.

  3. Multiple Frame Copies • Host X sends a unicast frame to router Y. • MAC address of router Y has not been learned by either switch yet. • Router Y will receive two copies of the same frame.

  4. MAC Database Instability • Host X sends a unicast frame to router Y. • MAC address of router Y has not been learned by either switch. • Switches A and B learn the MAC address of host X on port 0. • The frame to router Y is flooded. • Switches A and B incorrectly learn the MAC address of host X on port 1.

  5. Spanning-Tree Protocol • Provides a loop-free redundant network topology by placing certain ports in the blocking state.

  6. Spanning-Tree Operation • One root bridge per network • One root port per nonroot bridge • One designated port per segment • Nondesignated ports are unused

  7. Spanning-Tree Protocol Root Bridge Selection • Bpdu = Bridge Protocol Data Unit (default = sent every two seconds) • Root bridge = Bridge with the lowest bridge ID • Bridge ID = • In the example, which switch has the lowest bridge ID?

  8. Spanning-Tree Port States • Spanning-tree transits each port through several different states:

  9. Spanning-Tree Port States (Cont.)

  10. Spanning-Tree Path Cost

  11. Spanning-Tree Example

  12. Spanning-Tree Switch#show spanning-tree vlan 1 VLAN0001 Spanning tree enabled protocol ieee Root ID Priority 32769 Address 0001.96DC.1A62 Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Bridge ID Priority 32769 (priority 32770 sys-id-ext 1) Address 0010.1116.A3A4 Aging Time 300 Interface Role Sts Cost Prio.Nbr Type ---------------- ---- --- --------- -------- -------------------------------- Fa0/1 Desg FWD 19128.3 Shr Fa0/2 Root FWD 19128.3 Shr Switch(config)#spanning-tree vlan 1 priority 4096

  13. VTP Modes • Creates VLANs • Modifies VLANs • Deletes VLANs • Sends/forwards advertisements • Synchronizes • Saved in NVRAM • Creates VLANs • Modifies VLANs • Deletes VLANs • Forwards advertisements • Does not synchronize • Saved in NVRAM • Forwards advertisements • Synchronizes • Not saved in NVRAM

  14. VTP Operation • VTP advertisements are sent as multicast frames. • VTP servers and clients are synchronized to the latest revision number. • VTP advertisements are sent every 5 minutes or when there is a change.

More Related