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
Hi, is there a way to set a default gateway for the Management Interface - or is the accesss only possible from the same network Segment? By Sebastian.Schubert on October 19, 2020
Hello, the s3900 management port is not isolated from the service interface, so you only need to write a default route. For example: IP route 0.0.0.0 0.0.0.0 10.32.133.254 By FS on October 20, 2020
My switches are running the most recent release of the software available, but the ssh server implementation is so ancient that it cannot interoperate with even a four-year-old Ubuntu 16.04 client. When can this be fixed? By Garrett.Wollman on August 26, 2020
Hello, our switch supports ssh2.0, please describe in detail "the implementation of sh server is so old". Asymmetric encryption support: RSA1, DSA2 Symmetric encryption support: AES-128, AES-192, AES-256, 3DES, des_cbc, Blowfish HASH support: MD5, SHA1 By FS on August 27, 2020
After the S3900 switches are stacked, the device has lost the stacking port. What is the reason? By henson on June 19, 2020
After the S3900 switch is successfully stacked and you check the port status through the commands, the two stacking ports of the device will disappear which is a normal situation. It is mainly to prevent misoperation. Please don't worry. By FS on June 19, 2020
Why is the calendar set time of the switch restored after restarting? By Emoef on June 18, 2020
The time of calendar set is not saved in the configuration file so it will not continue counting after the device is turned off. It is recommended to use the ntp service to synchronize the system time, so that after the switch restarts, you only need to set the next restart time, and don‘t need to set the system time again. By FS on June 18, 2020
When multiple S3900 switches are stacked, one of them will go down. Will it affect the normal operation of other switches? By Soucie on June 16, 2020
If the master is down, it will re-elect, the election process is the same as the first stack. If it is a slave downtime, there will be no impact. By FS on June 16, 2020
Can the stacking and LACP functions of the S3900 be used together? By Helfer on June 15, 2020
Yes, after the S3900 switches are stacked, they are logically one device and can implement LACP with other devices. By FS on June 15, 2020
Hello, why do I fail to upload firmware to the S3900 switch when upgrading the switch? By Dennis Haislip on June 12, 2020
The S3900 series switches only support a maximum of 2 firmwares. Please use the command dir to check whether there are currently two firmwares. If so, you need to delete one and add the new one. If there is only one, please check whether the firmware is damaged. It is recommended to download and install again. By FS on June 12, 2020
Does the S3900 switch support https import certificates? By Shuford on June 11, 2020
Yes, but there are some requirements for the size of the certificate, the maximum is 5KB and the key is 2KB. By FS on June 11, 2020
When configuring QinQ, how many QinQ can be configured for each port? By Jimmina on June 10, 2020
The S3900 series are the access layer switches, which have certain restrictions on the hardware, so the maximum entry for QinQ is 24 per port. By FS on June 10, 2020
Hello, i see you need a solution for your network; our tech and salers can help you design your whole network solution with best quality and price. And we recommend the S3900-24T4S for you to connect to the server. The function of the core switch is more abundant than that of the access layer switch. So as for the core switch, we recommend S5800-8TF12S for the core switch. By FS on June 9, 2020