Spanning Tree Protocol
Spanning Tree Protocol (STP) is a standard technology used to prevent traffic looping over redundant connections between switches. The basic concept of STP is for every group of redundantly connected switches, one of the redundant links between the switches is automatically put into an idle state, preventing traffic from looping between switches. The value of STP is if one of the active links fail, the idle link will automatically become active, thus allowing both redundancy and loop prevention.
The 2026 supports a faster version of STP called Rapid Spanning Tree Protocol (RSTP). RSTP works the same as STP, it simply converts the idle link to active faster.
To test RSTP on the ES-2026, I set up a redundant network between the ES-2026, a Linksys SRW2008 and a NETGEAR GS108T, which all support RSTP. I connected the Linksys to the NETGEAR, the NETGEAR to the ES-2026, and the ES-2026 to the Linksys, forming a redundant network among the three switches.
I connected port 3 on the ES-2026 to the NETGEAR and port 4 on the 2026 to the Linksys. Notice in Figure 7 that port 4 on the ES-2026 shows a status of Discarding. This means that RSTP has determined port 4 on the ES-2026 is the redundant port and thus port 4 will sit idle until a port failure activates it.
Figure 7: Rapid Spanning Tree Protocol (RSTP) config
To simulate a port failure, I disconnected port 3 on the ES-2026, which is the link connecting the ES-2026 and the NETGEAR. All three switches should now detect that a link between them has failed and RSTP should force a change. That means port 4 on the ES-2026 should go from a Discarding state to a Forwarding state, which it did (Figure 8).
Figure 8: RSTP failover to Port 4
RSTP is more complicated than this little test, but I covered the basic functionality. My goal here was to verify RSTP worked on the ES-2026 with other switches, and it does. For more advanced RSTP configuration, the ES-2026 has menu options to enable/disable STP, choose STP or RSTP, adjust the timers used by STP/RSTP, and edit settings on the switch that control which port becomes the idle port.
Although the majority of the ports on the ES-2026 are only 100 Mbps, the switch does support passing jumbo frames up to 10,240 bytes in size on the 1000 Mbps ports. Jumbo frame support is off by default, but enabled with a check box in the System > Switch menu.
I enabled jumbo frames and tested it with two devices connected to the 1000 Mbps ports. One of my devices supported 4088 byte frames, the other 7936 byte frames, so I expected 4000 byte frames to pass. Figure 9 shows I was able to pass up to 4046 byte frames over the ES-2026's Gigabit ports.
Figure 9: Jumbo frame test
The 2026 also supports trunking or Link Aggregation Groups (LAG) between switches. Trunking allows combining multiple physical links between switches into a single path for load balancing, redundancy, and increased bandwidth. Trunking can be set up statically or dynamically using Link Aggregation Control Protocol (LACP). Up to 12 trunks can be configured.
I set up a trunk with two ports between the ES-2026 and my GS108T. Static trunk setup was easy; simply create the trunk and assign the appropriate ports to be members of the trunk. Dynamic trunk setup is even easier. Assign the ports to the trunk on both switches, connect the ports, and let the LACP protocol detect the connection and set up the trunk.
The Partner Oper System ID in Figure 10 has the MAC address of the GS108T switch, showing that the ES-2026 has detected the GS108T and set up a trunk between the two switches.