Spanning Tree With Multiple Links
- Take multiple links and put it together to get more throughput.
- Ethernet uplinks most commonly
- Loops created from redundant links
- Only 1 active link, others blocked
- Spanning Tree Protocol (STP)
- Blocks on redundant links
- On by default on Cisco
Link Aggregation
- Bundle links together at Layer 2 or Layer 3
- Bundled links act as a single logical interface
- STP no longer blocks
- Modes:
- On (no negotiation)
- PAgP
- LACP
- Open and is a little bit better
- Sending messages over the other side (Negotiating)
- Needs to be configured on both end sides.
- If you have a failure in one of the links you are still good because you have all the other links to stay up
- Bandwidth is now equal to total in bundle
- Your maximum throughout doesn't go any higher but you can have more users running at maximum speed.
- Negates STP reconvergence if link fails
- Some venders call this a Trunk (in HP)
- Cisco calls Truck to One wire for many VLANs (a tagged link).