Hi,
I hope it is okay if I ask a configuration question here.
A couple of weeks ago, my internet dropped and I noticed that my DSL modem was rebooting. When it came back up I had a new public IP and I could no longer load most web pages. Other than google, the ones which would load were very slow. I was finally able to get a page to load which suggested this behaviour could be caused by a MTU problem. I tried lowering the MTU on one of my machines from 1500 to 1492 and the problem was solved.
I then went to all of my various computers and changed the MTU to 1492, except my iPad. Apple being Apple, does not allow users the ability to change things like MTU. This means that I can still not get to most web pages, etc, on my iPad.
Further searching brought up pages like: https://blog.cloudflare.com/path-mtu-discovery-in-practice/ http://rtoodtoo.net/path-mtu-ip-fragmentation-and-mss/
Given the info on those pages, I have tried to set advmss on my router to 1452, 1200, 1024, etc. But no matter what I do, I end up killing the routing completely. I have tried doing things like:
# echo 1 > /proc/sys/net/ipv4/tcp_mtu_probing # echo 1024 > /proc/sys/net/ipv4/tcp_base_mss or # ip route change 0.0.0.0/0 dev red0 advmss 1024
Obviously, those are not the correct way to get ipfire to set mss to a lower value. I am hoping someone can tell me the correct way to work around a broken "path MTU discovery" issue.
Thanks,
John