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Double NAT detected...


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 shows four internal hops before escaping private network addresses.  The NAS seems to identify this as double NAT...

Tracing route to []
over a maximum of 30 hops:

1 <1 ms <1 ms <1 ms
2 9 ms 8 ms 8 ms
3 9 ms 9 ms 14 ms
4 8 ms 13 ms 4 ms
5 7 ms 9 ms 10 ms
6 15 ms 25 ms 16 ms []
7 15 ms 16 ms 16 ms []
8 15 ms 16 ms 19 ms []
9 14 ms 16 ms 14 ms
10 17 ms 20 ms 15 ms
11 17 ms 16 ms 16 ms
12 17 ms 16 ms 16 ms []

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?



Hey Srauh. NAT occurs on a LAN network only, so you can rule out it being a Mediacom issue. Double NAT means you have 2 devices on your LAN that have their own firewall and DHCP. In addition to your Netgear router, your Synology device probably has its own internal DHCP/NAT. You might need to put the Synology into bridged mode, and open ports in your router with port forwarding.