Gsc3570 flapping Ethernet interface,


Hello all;
I have noticed very strange behavior with the gsc3570 Intercom. When I connect this station to the cisco 2960-x switch the intercom starts up normally. The displays goes up and works - I can acces the phone menu and other functions. The power inline on the switch port shows device connected and powered, but the Ethernet ports is flapping continuously - up…down…up…down.
No others errors are observed on the switch.
Dec 15 11:58:57: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/18, changed state to up
Dec 15 11:58:59: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/18, changed state to down
Dec 15 11:59:03: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/18, changed state to up
Dec 15 11:59:06: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/18, changed state to down
Dec 15 11:59:10: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/18, changed state to up
Dec 15 11:59:12: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/18, changed state to down
Dec 15 11:59:17: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/18, changed state to up
Dec 15 11:59:19: %LINK-3-UPDOWN: Interface GigabitEthernet2/0/18, changed state to down

I have tried different port and intercom configuration - vlan tagged port, access port, auto speed/duplex, speed duplex set for 100TXFD, cdp on/off, lldp on/off.
The power budget on the switch is OK. I have also add 2x power mode (to give the intercom avibility to consume 30W of power on connected port) - with the same effect.
I have upgraded the firmware on GSC to the newest beta available - nothing changes here.
Nothing helps here.

The only way to get the port up and running is to connect anything active to the second Ethernet port on the intercom - it could be another port on the same switch, port in pc, or any other device with active Ethernet port
When the port has gone up I can disconnect the second port in the intercom and it works without any problems till next reboot.
I have made some tests with thee devices and two different Cisco switches - the behavior of gsc3570 is always the same.
I need to connect the second port to get the first one (with PoE) to go up.
I have connected to the same switch GDS3170 video doorphone about 20 gxp1625 phones and all these devices work without any issues.
I have no idea - its look like a bug - the device need to both ports connected on startup to bring up the Ethernet interface(and this is the only way to get it work). Could somebody help?


I think this might be hardware compatibility issue, or the GSC3570 is faulty.

Please try this to rule out and find the root cause of the issue:

  1. If you have other PoE switch, like the $100 Netgear or Linksys dumb unmanagable PoE switch, try it to see whether the GSC3570 has the same issue. If it is, then contact HelpDesk of Grandstream for RMA.
  2. Is the Cisco Switch Gigabit? What model name is your Cisco gear? If your Cisco swtich is giga, change it back to 100 Mbps and try again. I have a Lenovo laptop with Intel Gaga NIC card has similar issue, not working with Netgear GS108T but working fine with FS108P, incompatibility of the chips used between two.
  3. Plug a 2A (must be 2A) USB cable (most new cell phone charger now is 2A, just need to find a correct USB cable) to GSC3570 while connecting to any non- PoE switch, see whether it working as normal. Some PoE switch boasting will provide 30Watt per port but in reality it is NOT. I see this happened and using multi-meters to measure and confirmed. I forgot the name of the switch vendor (not popular one).

Hope this helps. Thank you for using GSC3570.


Hello GS_Guy
As I said in my original post - i have been done every of works you suggest. (without connecting usb power supply - i will connect it today)
My switch is Cisco 2960-x 1GBE model (fully managed). The poe port is configured for 30W. The PoE module has about 40%Power reserve now (I have two poe modules 370W each)
Changing port configuration to 100BaseTX or any other configuration provided for Ethernet port on the switch does not gives any effects. The PoE is not Issue here, because the GSC3570 starts normally. I could access any function using the display (without network functions of course)
The GSC3570 does not brings the link layer on eth, it brings it up, mac address is being stored in the mac address table in the switch and then GSC3570 disable Eth link on the port. And againg brings it up …and down.
The only working solution is to connect the second port in the GSC3570 to any active equipment (without poe) - then everything start working. Its look like the second port is being bridged with the PoE port and when it is down, the system down the Ethernet link on the first port. When both ports are connected - system starts normally. In this setup (with two connected Ethernet ports) I could also remove Ethernet link from the second port after the system brings up ETH link and system still works without any issues!! Till next reboot.
For me it is some kind of bug. I also does not see any errors in the switch debug log - just standard “link up/down” on the peer side.

OK i have made tests with 2A USB charger - The GSC3570 works only with the secondary ETH port. When I connect USB + first (marked as PoE) port to the switch (without poe) - system does not brings up the Ethernet link.
When I use the second port - it works without any issue.
Looking at this the issue is in ETH ports in GSC GSC3570 - to work correctly system needs to have secondary port active to bring up Ethernet Link on the port marked as PoE


@witekprytek: Could you help to advise MAC address and P/N number of your GSC3570? What is the firmware version now used? Thanks.


Product Model GSC3570
Part Number 9630005914A
Mac address C0:74:AD:1C:6C:F4
Software Version
I have the same issue on the official 1.03.x firmware


This is the only GSC3570 having such issue, correct?


After you upgrade to, have you performed factory reset for this device?


@witekprytek: Is this the only device having this flapping issue? I seems cannot duplicate the problem you had. All my GSC3570 seems working good with only PoE plugged, although it takes about 1 minute or so when plugged to Cisco PoE switch to get IP address but finally it will get IP address. Please help to advise. Thanks.


Yes I did


No I can observe same behavior on all (3 pcs) devices I have. This issue is only present when the device is connected to Cisco 2960-x or Cisco 3560CX switches (fully managed). Other PoE (unmanaged) switches works fine. It must be an issue with ETH link layer protocol between Cisco and Grandstream. It is very strange behavior because in the same switch all other Grandstream devices e.g GXP1625 phones, and other PoE powered Ethernet devices works fine. (I have some access points etc.) I have also gds3710 connected to the same switch and it works fine - even if I connect it to the same port as GSC3570.


Problem sounds like an issue with the cisco switch auto negotiation for port speed…

I only skimmed your info but have you preset the nic on the cisco where the gds is plugged into?

start with 100 mb fd and see if that is stable…

I have seen this behaviour with intel nic chips - only way to fix it is to set it at the nic level


This is not auto-negotiation problem. The speed and duplex are negotiated correctly - link is up for a moment and then GSC3570 switch the link down - (GSC not cisco - I can observe it on the switch console). When second port is connected there is no such a behavior, so it is not port speed and duplex negotiation problem. I have been told about it in my previous posts. I could set the link in any combination 100/FD 10 FD, 100/half 1GE - and the issue is still present.


@witekprytek: Please contact me via email.


@scottsip: Yes, I see this problem either with Intel® 82579LM Gigabit NIC with NetGear FS108P PoE switch. My laptop is using Intel 82579 NIC chip Gigbit, it never works when plug it into NetGear FS108P switch, the link LED is ON/OFF continously, no matter how I adjust settings in my computer. But when I switches it to other Switch like NetGear GS108T, it started working immediately.


FS108P uses the same realtek ethernet switch chip as GSC3570


@witekprytek: FS108P does not have issue with GSC3570. What I said is my laptop NIC (which is Intel chip, Gigabit) has issue with Netgear dual-speed hub/switch.


I did not say that there is problem between fs108p and gsc3570, but that both devices uses the same Ethernet chip. So both of them could produce similar issue when are connected to other Ethernet devices.
It shows that the Realtek chip family used in fs108p and gsc3570 have some internal bug.


@witekprytek: So you are saying you connecting fs108p to the Cisco switch it does NOT have the issue where GSC3570 has?


Problem is with cisco. Probably energy saving or similar settings.
I seen this multiple times.


No. I’m just saying that fs 108p and GSC3570 uses the same Ethernet chipset family RTL830x.
I had 108p switch in the past and I have observed the same issue with this switch as I can observe with the GSC3570 now and you have observed with your 108p switch. The ethernet connection could not be established with some other devices - cards, another switches etc. If we can reproduce the same issue with different devices and these devices uses the same realtek chipset family we can assume that something is wrong with this chipset not other devices.