Should traffic with these IP addresses get through

  Batch 18:59 07 Jan 2008
Locked

When I first got broadband (nearly 3 years ago) and installed a 3Com router, I found that Zone Alarm rarely blocked any incoming TCP / UDP scans / attacks etc. (because they were being stopped by the router). Those that did get through (to ZA) had a destination IP as allocated by my ISP (and used by the router facing out to the external world on the Internet). I didn't really give these anythought at the time, but with hindsight, it seems odd that these should be passed on to the PC with the "extermal" IP as the destination IP. Maybe that's part of my ignorance though.

Anyhow, lately I've seen scans etc. getting through to (and blocked by) ZA with a destination IP of my private IP range (e.g. 192.168.1.17). These source IPs are generally in Russia, Poalnd etc. My question really relates to these. These information in ZA suggests that the remote (source) IP is sending out traffic with a destination IP of 192.168.1.17. But how does this even get routed (to me), as surely it must be routed (over the Internet) using the external IP as allocated by my ISP? In any event, surely the router should not route (over my LAN) any traffic from the Internet that is using IP addresses in one of the private IP ranges (isn't that very basic security)?

One additional piece of information. The 3com router was replaced a few months ago (under warranty) as the original one went belly up. 3Com sent me a later model. It has teh latest firmware installed.

Any info that can shed light / educate would be useful.

  Batch 18:16 21 Jan 2008

Aplogies.

Ignore my posting of 18-1-08. I just realised that, on the day concerned, I made a very rare foray into the world of dial-up in order to be able to upload some updates to a website that is still hosted on a dial-up ISP free hosting service. SO the router wasn't even in play.

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