our problem with phones and ipads, when they trying to log in to Facebook the pics didn’t appear…
so I put an ordinary router connected to our cache server with static IP to test it by phone and every think is ok !!!
then I connect this router to mikrotik with a static ip too , but we still have the same problem …
then we put RB 1200 with only masquerade rule ( no firewall. NAT, Mangle, …) and connect the ordinary router to it , also phone can’t open pics in Facebook !!
yes at the beginning I thought that was the prob. so I changed the mtu to 1462 in customers routers but same prob.
(off course the mtu in pppoe server is 1480)
because of that I tried static ip and you know the mtu of it is 1500…
I had many different trade marks (tplink, dlink, mikrotik,…) routers used by customers and all of them are at 1480 or 1462 , their pcs work probably but the problem is in phones and ipads …
The mtu of a static ip is not 1500. It is whatever your ISP or upstream router uses. If you use DSL or PPPOE, you shoud not use 1500, even if you have a static IP.