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New Modem, New IPv4 Adress -> strange behaviour

Started by Walter H., January 27, 2022, 10:34:56 AM

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Walter H.


I have besides the HE-IPv6-Tunnel a self-made 6in4-Tunnel for my own;
the host what is called POP is also operated be myself;

where would someone start to look for the problem ...

behind the ISPs router I have my own router; which has a RFC1918 IP on the WAN side,
and the ISPs router has the official IPv4 on its WAN-side;

e.g. on my router I see this on tcpdump

19:26:43.687781 IP RFC1918-IPv4 > POP-IPv4: IP6 prefix::1 > 2001:470:100::2: ICMP6, echo request, seq 18440, length 40

on the POP itself this:

19:26:43.720708 IP MY-PUBLIC-IPv4 > POP-IPv4: IP6 prefix::1 > 2001:470:100::2: ICMP6, echo request, seq 18463, length 40
19:26:43.720753 IP POP-IPv4 > MY-PUBLIC-IPv4: IP6 2001:470:100::2 > prefix::1: ICMP6, echo reply, seq 18463, length 40

as you can see, the packets go out of my router (my 6in4-gateway), through the ISPs router and my POP
and also back through the POP, but my router doesn't get them;

where is the probable mistake or can't I do anything?


p.s. the HE-Tunnel doesn't work either because of the same reason;

Walter H.

the reason of this strange behaviour:
the new modem had bugs in its firmware, which doesn't go conform with the requirements to let packets with protocol 41 untouched;

I got a new one which indeed was an old one, that doesn't touch the packets with protocol 41