[Astlinux-users] MTU/MSS Problem with new carrier internet services

[Michael K. <mic...@ip...>]

Hi Group

I have changed my internet provider and I am having connectivity problems to some sites on Astlinux.
I am fairly certain that it is an MTU/MSS issue as I have fixed it on my Mikrotik router by adjusting this value.
Funny that I'm having problems with this provider but not on my previous provider. Both are using PPPoE and I tested that the maximum MTU for both is 1464 e.g.

3035-JSainsbury-CM1 kd # fping -M -b 1465 12000.ipcaccess.net
12000.ipcaccess.net: error while sending ping: Message too long
3035-JSainsbury-CM1 kd # fping -M -b 1464 12000.ipcaccess.net
12000.ipcaccess.net is alive

3076-VisionCF-CM1 kd # fping -M -b 1465 12000.ipcaccess.net
12000.ipcaccess.net: error while sending ping: Message too long
3076-VisionCF-CM1 kd # fping -M -b 1464 12000.ipcaccess.net
12000.ipcaccess.net is alive

Maybe my new provider is not allowing fragmentation?

Anyway just wondering how I fix this problem. Do I just set MTU using IFMTU in user.conf? E.g. IFMTU=ppp0:1460
Can I set the TCP MSS anywhere?

Regards
Michael Knill