Why is some HTTP traffic not getting through to Mikrotik?

Question

Computer networks

There are two routers, between them the L2TP (IpSec) tunnel is lifted.
Routes from the network (192.168.88.0/24) to the network (192.168.7.0/24) are registered, and accordingly back.
In the network of the first router, some sites (rbc.ru, avito.ru and others) do not open, but on the second everything is fine. There are no problems with the rest of most sites.
At the same time, when the tunnel is turned off, everything starts working.
I sin on the Firewall, but the pandemonium with the rules did not give any effect.
What could be the reason?

Answer 1

Check MTU. I am sure that when you raise the L2TP tunnel, the MTU on your bridge changes to a smaller side.

Answer 2

Do you have the Internet through the tunnel, or what?

Answer 3

At least show the configs, and then guess on the coffee grounds that you have set up not comme il faut there.

Answer 4

see firewall, nata and web proxy. I join the previous speaker, config in the studio.