- LAN Parties need Broadcast traffic for network discovery
- Many Networks rely on Spanning Tree and Fat-Links as Uplinks.
- Hub-Spoke Network Design
- Single Point of Failure
- Real topology on the floor is more like a grid of mesh
- L3 Networks can provide Failover and Load Balancing
- requires additional hardware
LAN Party networks need broadcast traffic for the local game discovery. This means that LAN party networks are usually a large layer 2 network. But large layer 2 networks with several hundret or thousand hosts are not that nice because the amount of broadcast that normal (Windows) computers send grows rapidly. Usually those networks are large hub-spoke designs. But this often results in very long cable runs if every switch has a direct to the core switch. The alternative to very long cables would be daisy chaining a lot of switches (or even building loops which would be disabled by spanning tree)
The "L3" networks I have seen are still a hub-spoke design on L1 and L2. Each access switch puts all its access ports into a VLAN. The gateway of that VLAN is somewhere on a core switch which does inter-VLAN routing. To get the required broadcast traffic between the seperate VLAN all those VLANs are also connected to a server. This server then uses software like  or  which listens for broadcast on all those VLANs and duplicates the received packets on all other VLANs. Depending on the software that is used either a white- or blacklisting is used.
This design has several disadvantages:
- The server that bridges the broadcasts is a single point of failure.
- The core switch is a single point of failure for the whole network
- The network cannot use redundant links for traffic because it still has to use spanning tree.
1 (Link zu service-discovery-helper) (Link zu bcast-bridge)