I see... Maybe isn't a problem at all, but have a look on this picture:
Inside VLAN20 there is another VLAN with a different VLAN ID and "use-service-tag=yes". Traffic seems flowing, but Im not sure if it is all ok. When I ping from RouterOS up to 1496 bytes it ping ok, but there are timeout when it is 1500. It should ping OK with 1500 till so fragment. Why it does NOT ping with 1497-1500 bytes then? Guess I will need to debug these packets...
*edit*
Found that interface ethernet where is installed the VLAN20 increases rx errors when pinging with 1500 bytes, pings 1496 long and lower do not increase rx errors.
*edit*
*edit2*
Interesting (just dunno why), pinging from 28 (Mikrotik minimum size) to 42 bytes, the output packet remains 56 bytes long always. I wonder if "packet size" on winbox means really it or some "payload". Also, response packets (echo reply) are proportional to request packets nominal size i.e: echo request size 56 with payload 41 down to 28 (things you can change the size) have a answer packet 55 bytes long down to 42. Is that a normal standard or just a MT implementation behavior?
28 bytes echo request (packet size 56):
000c 422d b7ca 001d 0924 65b8 0800 4500 ..B-.....$e...E.
001c db17 0000 ff01 b7c5 0a80 0a01 0a80 ................
0a03 0800 2dd2 fc27 ce05 0000 0000 0000 ....-..'........
0000 0000 0000 0000 ........
42 bytes echo request (packet size 56):
000c 422d b7ca 001d 0924 65b8 0800 4500 ..B-.....$e...E.
002a dd42 0000 ff01 b58c 0a80 0a01 0a80 .*.B............
0a03 0800 863f fc27 b108 3165 b3aa 8797 .....?.'..1e....
185e b71f b076 d7f3 .^...v..
*edit2*