topic Re: recv rst from server or recv from zero win from server in General Topics

recv rst from server or recv from zero win from server

Juns_Net — Fri, 16 Jan 2026 02:43:29 GMT

I'm using Global Protect to connect to the server. When I open YouTube to watch videos or run a speed test, I always receive an RST packet or a zero window message from the server. Then the client disconnects from the VPN.

I want to know what's causing this?

I will show the tcp dump in attach.

Re: recv rst from server or recv from zero win from server

Juns_Net — Fri, 16 Jan 2026 05:47:52 GMT

To add to that, IP 196.192.81.50 is the server.

Re: recv rst from server or recv from zero win from server

BorislavP — Fri, 16 Jan 2026 07:12:25 GMT

Probably,

When you use GlobalProtect and open high-bandwidth applications like YouTube or a speed test, a huge amoint of data is sent very quickly through the VPN tunnel.

In this situation, the VPN gateway cannot process the traffic fast enough, so its internal buffers fills up. When that happens, the gateway temporarily tells the sender to stop sending data (this appears as a TCP Zero Window). Shortly, the connection is reset, which causes the VPN session to drop.

This is not caused by YouTube or the server.

I would check:
Dataplane cpu
#show running resource-monitor
#show system resources

#show counter global filter delta yes severity drop

Re: recv rst from server or recv from zero win from server

Juns_Net — Fri, 16 Jan 2026 07:53:56 GMT

Thank you for your reply. I have a few points to make:

1. I have implemented rate limiting. Even when the rate is limited to 20Mb (downlink) and 10Mb (uplink), the RST error still occurs.

2. When I receive a packet with win=0, the win value I received previously was 260000B, but when I receive another packet from the server, it has changed to win=0. If it's caused by high bandwidth , the win value shouldn't change so drastically all at once. Furthermore, the time interval between the two packets is only 100ms.

3. My PC connects to the VPN server via MiFi. This problem disappeared after I changed my SIM card.

Re: recv rst from server or recv from zero win from server

Juns_Net — Fri, 16 Jan 2026 09:19:47 GMT

Thank you for your reply. I have a few points to make:

1. I have implemented rate limiting. Even when the rate is limited to 20Mb (downlink) and 10Mb (uplink), the RST error still occurs.

3. My PC connects to the VPN server via MiFi. This problem disappeared after I changed my SIM card.