The S3900 series switches consist of three models: S3900-24T4S, S3900-24F4S, S3900-48T4S, which are fully managed stackable Gigabit switches, equipped with Broadcom chips, supporting 10G SFP+ uplinks, designed for SMB, campus and enterprise networks.
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STP (Spanning Tree Protocol) is a Layer 2 protocol that runs on network switches. The main purpose of STP is to prevent the loop caused by redundant paths, avoiding the broadcast storm and MAC address table unstable. FS S3900 series high-performance Gigabit Ethernet L2/L3 Lite managed switches are suitable for home use, SMB, enterprise and campus networks. They support STP to provide link redundancy and backups while simultaneously preventing undesirable loops.
Figure 1 is the typical STP application on S3900 series switches. Switch A, Switch B and Switch C are all running STP. STP can eliminate the loop that may exist in the network by blocking redundant links, ensuring a loop-free network. In figure 1, Switch B is selected as the root of the spanning tree. The packets will go by PC 1 - Switch B - Switch C - PC 2, which is link 1. The STP algorithm can calculate the best loop-free path for transmission, so the port on Switch C that connected with Switch A is blocked. Link 2 that stands for PC 1 - Switch B -Switch A - Switch C - PC 2 is unavailable. If link 1 breaks down, STP can activate the blocked port on Switch C. Then the packets will go through by link 2, at last, the packet will successfully arrive at PC 2.
Note that, there are STP, RSTP (Rapid Spanning Tree Protocol) and MSTP (Multiple Spanning Tree Protocol).
RSTP is the improvement of STP. Because the STP network convergence speed is slow, IEEE introduced RSTP to provide significant recovery in response to network changes or failures. RSTP is backward compatible with standard STP. MSTP enables multiple VLAN instances to be mapped to the same spanning-tree without creating loops. It can generate multiple spanning trees that are used independently to deliver traffic in different VLANs.
FS S3900 series switches consist of S3900-24F4S, S3900-24T4S, and S3900-48T4S. All the switches support STP, RSTP and MSTP. They can be used with switches from vendors like Cisco and Juniper for configuring STP. Note that, RSTP is the default option of STP, while MSTP is usually used in a large enterprise environment.
Successful configuration of running STP, RSTP and MSTP on S3900 series switches can be achieved via CLI commands. There are four main steps to configure STP and RSTP on S3900 series switches.
Enable STP.
Configure the STP mode.
Configure the root bridge.
Verify the configuration.
Figure 2 is the networking diagram of STP/RSTP configuration on S3900 series switches.
S3900-24F4S-A-2(config)#spanning-tree
S3900-24F4S-A-2(config)#spanning-tree mode stp
S3900-24F4S-A-2(config)#spanning-tree priority 0
S3900-24F4S-B(config)#spanning-tree
S3900-24F4S(config)#interface vlan 1
S3900-48T4S-3(config)#spanning-tree
S3900-48T4S-3(config)#spanning-tree mode stp
S3900-24F4S-A-2#show spanning-tree brief
Spanning Tree Mode: STP
Spanning Tree Enabled/Disabled: Enabled
Designated Root: 0.ECD68A369C78
Current Root Port: 0
Current Root Cost: 0
S3900-24F4S-B#show spanning-tree brief
Spanning Tree Mode: STP
Spanning Tree Enabled/Disabled: Enabled
Designated Root: 0.ECD68A369C78
Current Root Port (Eth): 1/21
Current Root Cost: 20000
S3900-48T4S-A-3#show spanning-tree brief
Spanning Tree Mode: STP
Spanning Tree Enabled/Disabled: Enabled
Designated Root: 0.ECD68A369C78
Current Root Port (Eth): 1/1
Current Root Cost: 20000
Result: S3900-24F4S-A is set as the root bridge because of its highest priority. Eth 1/22 port of S3900-24F4S-B switch is blocked. Thus, a loop-free network is achieved.
S3900-24F4S-A-2(config)#spanning-tree
S3900-24F4S-A-2(config)#spanning-tree priority 0
S3900-24F4S-A-2(config)#spanning-tree mode rstp
S3900-24F4S-B(config)#spanning-tree
S3900-24F4S-B(config)#spanning-tree mode rstp
S3900-48T4S-1(config)#spanning-tree
S3900-48T4S-1(config)#spanning-tree mode rstp
S3900-24F4S-A-2#show spanning-tree brief
Spanning Tree Mode: RSTP
Spanning Tree Enabled/Disabled: Enabled
Designated Root: 0.ECD68A369C78
Current Root Port: 0
Current Root Cost: 0
S3900-24F4S-B#show spanning-tree brief
Spanning Tree Mode: RSTP
Spanning Tree Enabled/Disabled: Enabled
Designated Root: 0.ECD68A369C78
Current Root Port (Eth): 1/21
Current Root Cost: 20000
S3900-48T4S-1#show spanning-tree brief
Spanning Tree Mode: RSTP
Spanning Tree Enabled/Disabled: Enabled
Designated Root: 0.ECD68A369C78
Current Root Port (Eth): 1/1
Current Root Cost: 20000
Result: S3900-24F4S-A is set as the root bridge because of its highest priority. Eth 1/22 port of S3900-24F4S-B switch is blocked. Thus, a loop-free network is achieved.
Interface-based VLAN Configuration on FS S3900 Series Switches
Voice VLAN Configuration on FS S3900 Series Switches
Can a port group be a downlink port if the group is a trunk? By Chavers on May 1, 2022
Yes, if the port group is trunk type, it can also be used as a downlink port. By FS on May 2, 2022
How loud is it? I plan to use it in a homelab office and need to know if I will be able to sit next to it all day. Thanks By Harlan on March 14, 2022
It is fanless, so it's suitable for deployment in work areas or home scenes. By FS on March 15, 2022
Does this switch requires liscensing like the cisco types? By Aaron Laymon on March 14, 2022
It does not require a license, all the features listed are available directly on the switch. By FS on March 14, 2022
What are the dimensions? By Kilby on March 10, 2022
Physical dimensions 44 x 440 x 280mm(1.73'' x 17.32'' x 11.02''), this fits a standard19"rack slot with a minimum of 1U height. By FS on March 11, 2022
Does this switch come with rack mount ears and screws? By Herbert on March 9, 2022
Mine come with the ears and screws for the ears. By FS on March 11, 2022
Does the 10G Uplink port of this switch support the electrical interface module of FS? What happens to the rate? By Colby on January 1, 2022
The 10G port of S3900-24T4S switch can use FS electrical interface module, which has no impact on the rate. It only says that the electrical interface module is used with network cables, and the optical module is used with fiber optic cables. By FS on January 1, 2022
Does the switch support other operating systems besides FSOS? By Keith Carter on December 30, 2021
S3900-24T4S is a hardware and software integrated switch. It cannot be installed and adapted to other operating systems. By FS on December 30, 2021
Could you provide inter-VLAN routing and relevant documents? By Bruck on December 25, 2021
Hello, S3900-24T4S supports inter VLAN routing, You can refer to section 3.1 of this document: S3900 Series Switches Configuration Guide . By FS on December 25, 2021
Can the S3900-24T4S switch connect two routers and then segment the network? By Jacob on December 21, 2021
S3900-24T4S supports VLAN, L3 Static Routing, and QoS, which can meet your requirements for network segmentation. By FS on December 21, 2021
DHCP Server can be configured on S3900-24T4S switches, correct? By Goulet on December 17, 2021
I'm sorry you can't, it doesn't support DHCP Server. By FS on December 17, 2021