6 Jun
2016
6 Jun
'16
11:37 a.m.
I have a strong suspicion that my ISP (Charter
Communications) has implemented
some kind of filtering on my home cable-based (DOCSIS) internet connection. My
reception of the RIP44d table broadcase has all but ceased. ip-ip tunnel
communication to a friend's machine in a neighboring county only seems to work
for a limited time, and only AFTER I initiate a connection from my end. It's
as if they're using some kind of NAT or port knocking filter, and only opening
the gate for incoming proto 4 traffic for a limited time after I initiate an
outgoing request to a specific host.
It is, as Brian N1URO also wrote, an issue in your home router.
Other routers have shown this phenomenon for some time.
Even when you set a "DMZ" (meaning: forward all unknown traffic to this host),
there still is a stateful firewall in place for all protocols except TCP and UDP,
requiring you to send outgoing traffic before incoming traffic is accepted.
You will need to have the router put in bridge mode (making it only a modem) and
install a better router in front of that. With a suitable router, it can also
do the IPIP encapsulation. A Linux system of course is a suitable router as well.
Rob