jbertrand
Hello,
I'm trying to optimize two OpenVPN links between a Linux server and a NetBSD client. This link use UDP datagrams.
Largest ping I can send between both stations is :
ping -D -s 1464 -c 1 <ipv4 address>
Thus, I have added in server configuration :
link-mtu 1464
fragment 1420
mssfix 1424
to avoid fragmentation.
Same lines have been added in client configuration.
Nevertheless, I obtain in logs :
- client side:
Mon Jan 30 11:56:59 2017 WARNING: normally if you use --mssfix and/or --fragment, you should also set --tun-mtu 1500 (currently it is 1386)
Mon Jan 30 11:57:01 2017 OPTIONS IMPORT: WARNING: peer-id set, but link-mtu fixed by config - reducing tun-mtu to 1383, expect MTU problems
- server side :
Mon Jan 30 11:56:59 2017 130.193.2.25:10240 WARNING: normally if you use --mssfix and/or --fragment, you should also set --tun-mtu 1500 (currently it is 1306)
Mon Jan 30 11:56:59 2017 130.193.2.25:10240 WARNING: 'tun-mtu' is used inconsistently, local='tun-mtu 1338', remote='tun-mtu 1418'
On both sides, tap interfaces announce :
(server) tap2: flags=4098<BROADCAST,MULTICAST> mtu 1500
(client) tap1: flags=8802<BROADCAST,SIMPLEX,MULTICAST> mtu 1500
I don't understand why with the same MTU parameters, I obtain a "tun-mtu inconsistently used" message.
Any idea ?
Best regards,
JB
