Dears...

we have about 1500 PPPoE users ...

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 !!

is there any idea about that ?

our systems are X86 V 5.23

Sounds like an MTU issue. What mtu are you using for pppoe clients?

i bet you have a few other websites that don't work either. make sure you change the mtu to 1492.

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 ...

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.

Make sure you are on 5.22 the DNS bug has the same effect

Dears....

I was upgraded all of my RBs to 5.23 and the problem was solved ....

Best regards...