8021ad: MTU problems between atheros and ralink on ipv4

[nickbash11]

I have two devices based on atheros and ralink chips.
The problem is if I try to send packets more than 1428 between hosts, packets more than 1428 bytes just drop. Meanwhile ipv6 works fine.

# ping -s 1500 10.202.0.94
PING 10.202.0.94 (10.202.0.94): 1500 data bytes
^C
--- 10.202.0.94 ping statistics ---
4 packets transmitted, 0 packets received, 100% packet loss

# ping -s 1428 10.202.0.94
PING 10.202.0.94 (10.202.0.94): 1428 data bytes
1436 bytes from 10.202.0.94: seq=0 ttl=64 time=6.061 ms
1436 bytes from 10.202.0.94: seq=1 ttl=64 time=1.446 ms
1436 bytes from 10.202.0.94: seq=2 ttl=64 time=1.398 ms
1436 bytes from 10.202.0.94: seq=3 ttl=64 time=1.458 ms
^C
--- 10.202.0.94 ping statistics ---
4 packets transmitted, 4 packets received, 0% packet loss
round-trip min/avg/max = 1.398/2.590/6.061 ms

# ping -s 1500 fd66:66:66:7:b2b2:dcff:fd3a:b35c
PING fd66:66:66:7:b2b2:dcff:fd3a:b35c (fd66:66:66:7:b2b2:dcff:fd3a:b35c): 1500 data bytes
1508 bytes from fd66:66:66:7:b2b2:dcff:fd3a:b35c: seq=0 ttl=64 time=1.528 ms
1508 bytes from fd66:66:66:7:b2b2:dcff:fd3a:b35c: seq=1 ttl=64 time=1.283 ms
1508 bytes from fd66:66:66:7:b2b2:dcff:fd3a:b35c: seq=2 ttl=64 time=1.254 ms
1508 bytes from fd66:66:66:7:b2b2:dcff:fd3a:b35c: seq=3 ttl=64 time=1.413 ms
^C
--- fd66:66:66:7:b2b2:dcff:fd3a:b35c ping statistics ---
4 packets transmitted, 4 packets received, 0% packet loss
round-trip min/avg/max = 1.254/1.369/1.528 ms

that's the same node with ip 10.202.0.94 and fd66:66:66:7:b2b2:dcff:fd3a:b35c based on ralink:

# cat /proc/cpuinfo
system type : Ralink RT3352 id:1 rev:6
machine : D-Link DIR-620 D1
processor : 0
cpu model : MIPS 24KEc V4.12
BogoMIPS : 255.59
wait instruction : yes
microsecond timers : yes
tlb_entries : 32
extra interrupt vector : yes
hardware watchpoint : yes, count: 4, address/irw mask: [0x0ffc, 0x0ffc, 0x0ffb, 0x0ffb]
isa : mips1 mips2 mips32r1 mips32r2
ASEs implemented : mips16 dsp
shadow register sets : 1
kscratch registers : 0
package : 0
core : 0
VCED exceptions : not available
VCEI exceptions : not available

I came across with this problem only on ralink chip.

config switch
option name 'rt305x'
option reset '1'
option enable_vlan '1'

config switch_vlan
option device 'rt305x'
option vlan '1'
option ports '0 1 2 3 5 6t'

config device 'eth0_1_12'
option type '8021ad'
option name 'eth0_1_12'
option ifname 'eth0.1'
option vid '12'
option proto 'static'
option ip6addr 'FD02:0:0:B0B2:DC3A:B35C:0:212/128'

config interface 'eth0_1_12_ad'
option ifname 'eth0_1_12'
option auto '1'