My Sagemcom F@st 3868 cable gateway (modem-router combo) has four devices on its LAN ports: a PC, a Hardware Firewall, a Cable TV Switch and a VoIP Adapter. The GRC Shields UP! test showed several ports Closed but not Stealthed. I have forwarded all the Closed ports found by Shields UP! to the Hardware Firewall, which has Stealthed them. However, Port 0 is still not Stealthed and there is no way to forward it to the Hardware Firewall. The gateway also has a built-in firewall but even setting it to High does not resolve the issue, probably because the RTP and SIP ports are forwarded to the VoIP Adapter, which requires them to work. Any suggestions for how to Stealth Port 0 will be appreciated. Thanks.
Thanks for the post-back and information.
SA
I have a new ISP and a new DSL gateway all of whose ports are stealthed (filtered). The issue has been resolved. I would warn all Norton Community members against buying any Sagemcom equipment or using an ISP who does. Thanks.
Hello again. I'm following up to see if we can assist further?
SA
Hello Groucho777. I've searched and seen several posts by you in other forums regarding port 0. First off, port 0 DOESN'T officially exist, therefore it cannot be stealthed. Port 0 is a reserved port in TCP/IP networking. Have you also read this thread about Shields Up and probing port 0 on that site? Programming language will point to the OS to allow it to select a port for traffic created as destined for port 0, as well as firmware on a router. The latter is the reason port 0 is showing as closed yet not stealthed. If you are a Windows user and on version 2004 or 20H2 there are built in protections provided by Defender that run even with the existence of 3rd party antivirus software. Norton's firewall also complements those protections. Port 0 also cannot be stealthed using the Norton Firewall. Hope that helps a bit.
SA