Mixing Speed Compatibility 2.5Gbps <--> 1 Gbps XS1930-10, XS1930-12HP or XGS1210-12

Av3ng3r
Av3ng3r Posts: 10  Freshman Member
First Comment Friend Collector Second Anniversary
edited September 2022 in Switch
Hi Support Zyxel and community,

I decided to upgrade to APs coming with a 2.5Gbps port just to find that some switches do not like or fully support this configuration, 2.5Gbps <--> 1Gbps with or without flow control. Basically, every time I have a 2.5Gbps AP port communicating to a 1 Gbps device the max upload speed from the 2.5Gbps to the 1 Gbps is maxed out at 500 Mbps without flow control and 700 Mbps with flow control. If I change the AP port to 1 Gbps speeds are around 980Mbps.

Do you know if the XS1930-10, XS1930-12HP or XGS1210-12 are capable of supporting full ~980 Mbps bi-directional ( Upload/Download) between 2.5 Gbps and a 1Gbps port?

has this been tested?  Any experiences?

I am planning to buy 2 of any of the above Zyxel but would like to know in advance if this 2.5Gbps <--> 1 Gbps is NOT a problem.

All Replies

  • Zyxel_Melen
    Zyxel_Melen Posts: 2,577  Zyxel Employee
    Zyxel Certified Network Engineer Level 1 - Switch Zyxel Certified Network Administrator - Switch Zyxel Certified Network Administrator - Nebula Zyxel Certified Sales Associate
    Hi @Av3ng3r,
    Welcome to Zyxel community!Since the switch models that you mentioned both support 2.5Gbps ports, I think you should link the AP and switch in both 2.5Gbps.When you connect at 2.5Gbps <--> 1Gbps, the speed duplex is mismatched, it causes packet loss and the slow speed result.In order to get good performance, I suggest linking the AP and switch in both 2.5Gbps.
    Zyxel Melen


  • Av3ng3r
    Av3ng3r Posts: 10  Freshman Member
    First Comment Friend Collector Second Anniversary
    Hi Melen,

    Thank you for your reply. Let me provide more context. The problem is not between the AP and the switch but the communication through the switch when the transmitting endpoint on one port of the switch is communicating to another endpoint connecting to the switch at different speed.  Please see below.


    Laptop < ---  RX/TX WiFi rate 2402 Mbps RSSI -35dbm--->AP <- 2.5Gbps Wired ->Switch XYZ<- 1.0

    Gbps Wired -> Server or Laptop.

    On the above scenario, multiple switches cannot handle the communications with buffer or flow control.

    The question I have is if the XS1930-10, XS1930-12HP or XGS1210-12 have been tested successfully to handle the above configuration. 

    I would appreciate any feedback or experience with the above config.







  • Zyxel_Melen
    Zyxel_Melen Posts: 2,577  Zyxel Employee
    Zyxel Certified Network Engineer Level 1 - Switch Zyxel Certified Network Administrator - Switch Zyxel Certified Network Administrator - Nebula Zyxel Certified Sales Associate
    Hi @Av3ng3r,

    Thanks for sharing more detail with me.
    Based on the information you provided, upload is low throughput from 2.5G to 1G, but 1G to 2.5G should work well. 

    In 2.5G to 1G scenario, it will trigger both end workstations to enlarge their TCP window size, which means they tend to send more packets at a time. 

    This will start challenging the Switch packet buffer. 

    In this case, the client will send more packets at a time in 2.5Gbps speed to 1Gbps port where the server is, so the packet buffer ultimately will have its limitations. This is the reason you start seeing poorer results. 

    Also, the poorer results can be due to network latency which is any kind of delay it takes for data or a request to go from the source to the destination over a network.  

    In real world, throughput varies from site to site, but don’t forget, it’s also multi-TCP sessions in real case, and that will stack up the throughput too. 
    Zyxel Melen


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