I've been a Mediacom customer for many years. I have my own Arris SB8200 modem and use a Netgear Orbi WiFi and router.
There is a Synology NAS on my internal network for raided storage of my photos, music and documents. The Synology complains about a double NAT when trying to configure for my router. A traceroute to 8.8.8.8 shows four internal hops before escaping private network addresses. The NAS seems to identify this as double NAT...
Tracing route to dns.google [8.8.8.8]
over a maximum of 30 hops:
1 <1 ms <1 ms <1 ms 192.168.0.1
2 9 ms 8 ms 8 ms 10.158.224.1
3 9 ms 9 ms 14 ms 172.30.4.41
4 8 ms 13 ms 4 ms 10.16.80.127
5 7 ms 9 ms 10 ms 10.16.80.21
6 15 ms 25 ms 16 ms 68-66-73-109.client.mchsi.com [68.66.73.109]
7 15 ms 16 ms 16 ms po13.chgil001cr1.mchsi.com [68.66.72.41]
8 15 ms 16 ms 19 ms po10.chgil001er1.mchsi.com [68.66.73.122]
9 14 ms 16 ms 14 ms 72.14.194.2
10 17 ms 20 ms 15 ms 74.125.251.183
11 17 ms 16 ms 16 ms 142.251.60.207
12 17 ms 16 ms 16 ms dns.google [8.8.8.8]
Trace complete.
Since I have only one router inside my home, this double NAT condition seems to be in Mediacom's network. Is there a fix?
