There are issues when ISPs fail to terminate RFC1918 addresses.
There are issues when ISPs fail to terminate RFC1918 addresses.
I explored the network path using a traceroute to those IPs, but the packets kept arriving until it stopped responding. My concern is whether this reveals any weaknesses or exploits. RFC1918 private ranges like 192.168.x.x are generally safe from external attacks since they're reserved and not publicly routable.
Observing the outcome reveals significant flaws in the implementation. A traceroute simply displays ICMP packets with TTL values rising at each hop. When TTL hits zero, the packet is discarded and the router responds with an expired TTL message. Interfaces may appear to support multiple IP addresses, but since responses are self-generated, they're incorrectly routed through interfaces using their main IP as the source. This isn't inherently problematic, but it reflects poor design for any interface exposed publicly. RFC1918 addresses are meant for private use and shouldn't be routable outside that scope. It's not about public exposure—it's about ensuring a consistent global primary IP is always used.
It's sending a packet because of TTL or Time To Live limits. This rule was designed to stop packets from circling endlessly. Each time a router forwards a packet, its count reduces by one. When it hits zero, it's marked as invalid and discarded, and a reply goes back to the sender.
This approach makes logical sense. Traceroute continues to add one hop at a time until it hits the target. Based on your setup, you might encounter 2–3 or even 6 different providers along the way. Ultimately, you'll hit a *timeout* indicating the destination isn't responding to ICMP packets.
You recently tested with a different provider, and the traceroute finished within that same ISP as the previous day.
It's likely you're verifying performance on the same network interface. I'm just trying to figure out your goal.