SoftEther VPN User Forum

Dear all,

I'm having an issue where there is constant traffic on the VPN port. I would imagine that once the VPN tunnel is created, I should not have that much traffic on the VPN port itself but rather in the tunnel. I have stopped all traffic in the VPN tunnel, but there is still around 9MB of data flowing between the server the client per hour. Is that normal?

Here is a capture of a few packets:
15:05:47.590514 IP (tos 0x0, ttl 110, id 12326, offset 0, flags [DF], proto TCP (6), length 40)
<client-ip>.58502 > <server-ip>.https: Flags [.], cksum 0x72cf (correct), seq 71, ack 14794, win 259, length 0
15:05:47.606327 IP (tos 0x0, ttl 64, id 20441, offset 0, flags [DF], proto TCP (6), length 295)
<server-ip>.https > <client-ip>.58502: Flags [P.], cksum 0x80a7 (incorrect -> 0x6ca8), seq 15462:15717, ack 71, win 632, length 255
15:05:47.649344 IP (tos 0x0, ttl 110, id 12327, offset 0, flags [DF], proto TCP (6), length 40)
<client-ip>.58502 > <server-ip>.https: Flags [.], cksum 0x6f37 (correct), seq 71, ack 15717, win 256, length 0
15:05:47.666261 IP (tos 0x0, ttl 64, id 20442, offset 0, flags [DF], proto TCP (6), length 271)
<server-ip>.https > <client-ip>.58502: Flags [P.], cksum 0x808f (incorrect -> 0x158d), seq 15717:15948, ack 71, win 632, length 231
15:05:47.706721 IP (tos 0x0, ttl 64, id 20443, offset 0, flags [DF], proto TCP (6), length 386)
<server-ip>.https > <client-ip>.58502: Flags [P.], cksum 0x8102 (incorrect -> 0x11b5), seq 15948:16294, ack 71, win 632, length 346
15:05:47.746185 IP (tos 0x0, ttl 110, id 12328, offset 0, flags [DF], proto TCP (6), length 40)
<client-ip>.58502 > <server-ip>.https: Flags [.], cksum 0x6e51 (correct), seq 71, ack 15948, win 255, length 0
15:05:47.746404 IP (tos 0x0, ttl 64, id 20444, offset 0, flags [DF], proto TCP (6), length 386)
<server-ip>.https > <client-ip>.58502: Flags [P.], cksum 0x8102 (incorrect -> 0x1e51), seq 16294:16640, ack 71, win 632, length 346
15:05:47.770974 IP (tos 0x0, ttl 64, id 20445, offset 0, flags [DF], proto TCP (6), length 111)
<server-ip>.https > <client-ip>.58502: Flags [P.], cksum 0x7fef (incorrect -> 0xa279), seq 16640:16711, ack 71, win 632, length 71
15:05:47.790556 IP (tos 0x0, ttl 110, id 12329, offset 0, flags [DF], proto TCP (6), length 40)
<client-ip>.58502 > <server-ip>.https: Flags [.], cksum 0x6b99 (correct), seq 71, ack 16640, win 259, length 0
15:05:47.842398 IP (tos 0x0, ttl 64, id 20446, offset 0, flags [DF], proto TCP (6), length 386)
<server-ip>.https > <client-ip>.58502: Flags [P.], cksum 0x8102 (incorrect -> 0x5e87), seq 16711:17057, ack 71, win 632, length 346
15:05:47.842460 IP (tos 0x0, ttl 64, id 13259, offset 0, flags [DF], proto UDP (17), length 116)
<server-ip>.40196 > <client-ip>.64079: [bad udp cksum 0x7fff -> 0xd808!] UDP, length 88
15:05:47.857062 IP (tos 0x0, ttl 110, id 12330, offset 0, flags [DF], proto TCP (6), length 40)
<client-ip>.58502 > <server-ip>.https: Flags [.], cksum 0x6b52 (correct), seq 71, ack 16711, win 259, length 0
15:05:47.861925 IP (tos 0x0, ttl 64, id 20447, offset 0, flags [DF], proto TCP (6), length 317)
<server-ip>.https > <client-ip>.58502: Flags [P.], cksum 0x80bd (incorrect -> 0x583e), seq 17057:17334, ack 71, win 632, length 277

I'm wondering why I have the "incorrect" messages here. Can that be the cause of the high traffic I'm getting?

Kind regards,
Stephane

I think server NIC driver is broken.
I think the NIC failed offloading.