Unable to load VPN gateway page properly – stuck at loading – ADC sends reset code 9826

Load balancing virtual server or VPN VServers does not work fine with protocol HTTP/HTTPS.

Sporadically, some contents (images, javascripts, etc.) on the VPN Gateway login page do not load properly or page stuck at loading with progress spinning circle.

Upon detailed review of a network trace capture the are Reset codes coming from ADC with RESET code 9826 under “Window Size Value” in TCP parameter.

Example of content: jquery-3.3.1.min.js

HTTP GET :: /logon/LogonPoint/receiver/js/external/jquery-3.3.1.min.js

ADC responds with TCP RESET : Windows Size Value: 9826

Transmission Control Protocol, Src Port: 443, Dst Port: 50937, Seq: 57901, Ack: 1653, Len: 0

Source Port: 443

Destination Port: 50937

[Stream index: 7]

[TCP Segment Len: 0]

Sequence number: 57901 (relative sequence number)

Sequence number (raw): 2250568975

[Next sequence number: 57901 (relative sequence number)]

Acknowledgment number: 1653 (relative ack number)

Acknowledgment number (raw): 1242823613

0101 …. = Header Length: 20 bytes (5)

Flags: 0x014 (RST, ACK)

Window size value: 9826

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