How to test for ISP dropping Protocol 41 traffic?

[wrtpoona]

I moved to a new location and my he.net tunnel receives no data (OpenWRT current).
There's just a single ISP serving this neighborhood and it is not my old ISP on which he.net worked fine.

OpenWRT he.net config:

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config interface 'wan6'
option proto '6in4'
option peeraddr '209.51.161.14'
option ip6prefix '2001:470:8c1f::/48'
option tunnelid '***748'
option username '*******'
option password '********'
option mtu '1424'
option ip6addr '2001:470:1f06:8df::2'
option defaultroute '1'

iptables rules are in place to allow Proto 41:

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root@apu:~# iptables-save | grep 41
-A INPUT -p ipv6 -m comment --comment Allow-Protocol-41 -j ACCEPT
-A OUTPUT -p ipv6 -m comment --comment Allow-Protocol-41 -j ACCEPT
-A zone_wan_input -s 209.51.161.14/32 -p ipv6 -m comment --comment "!fw3: Allow-Protocol-41" -j ACCEPT

root@apu:~# ip tunnel show
sit0: ipv6/ip remote any local any ttl 64 nopmtudisc 6rd-prefix 2002::/16
6in4-wan6: ipv6/ip remote 209.51.161.14 local ***.***.208.191 ttl 64 6rd-prefix 2002::/16


The log shows the link as up, but only a few packets are sent, but zero are received:

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Fri Jan 25 13:52:03 2019 daemon.notice netifd: Interface 'wan6' is setting up now
Fri Jan 25 13:52:03 2019 daemon.notice netifd: Interface 'wan6' is now up
Fri Jan 25 13:52:03 2019 daemon.notice netifd: tunnel '6in4-wan6' link is up
Fri Jan 25 13:52:03 2019 user.notice firewall: Reloading firewall due to ifup of wan6 (6in4-wan6)

I've tried changing MTU to 1480 and 1280, no cigar.
How would I test if this new ISP is silently dropping Protocol 41?

[cholzhauer]

You'd have to run something like Wireshark to see what's going on.

Have you tried it without the firewall?

[kriteknetworks]

I moved to a new location...

Did you update your tunnel details with your new IP?