Double NAT
Double NAT
Hello everyone. After upgrading to VDSL2, I faced challenges with my current modem/router because it doesn’t support the new standard. My provider’s device is outdated and limits features like DNS changes. I was considering a replacement but wanted to stick with my existing setup. I’m curious about the effect of keeping NAT enabled on either modem—would it cause noticeable latency, or should I disable it entirely? Or is it better for both devices to maintain NAT?
Double NAT may cause performance problems and stability issues. Disable it on one device.
I would pass through the edge, with only a single NAT layer managed by the downstream router. Double NAT functions adequately for everyday browsing and comparable tasks, though it may become inconsistent if NAT timeouts vary or if one segment struggles to handle traffic compared to another (creating a bottleneck). For services requiring forwarding, you'd need to route them twice, ensuring UPNP stays outside your boundary NAT.
Thank you for your feedback. I turned off the service on the first modem but encountered some problems now. My ISP uses PPPoE and provides a dynamic IP address. I switched to PPP and NAT on the second modem, which connects via WAN to LAN using PPPoE. Internet access works well, though it assigns me a public IP that isn’t reachable outside the network. When I ping my public IP, it doesn’t respond, even though traceroute shows it with a low latency and tries again without success. After about 30 minutes, it does respond.
I also have another modem handling the connection—assigning it the IP 192.168.1.1 while the primary one gets 192.168.1.254. The primary modem doesn’t ping or allow access. If I connect its Ethernet, the secondary router appears, but I can’t ping it or reach it. Since PPPoE is used and I’m trying to enable PPP and NAT, it seems the ISP might have different NAT configurations depending on the settings. It appears you could be receiving two public IPs.