> Maybe you got a new IP-address from Shaw when you reboo...

[mdk]

> Maybe you got a new IP-address from Shaw when you rebooted the modem?

Doubtful.  It's been my experience that a reboot just "renews" the current DHCP-lease, thus keeping the same IP-address. This is useful for when I am at work, and want to connect, through my cable-modem, to one computer on my home network -- I always know the IP-address of the cable-modem.

When I logon to the web-interface of my XB7 cable-modem, I see: DHCPv4 Lease Time: 2d:0h:0m 

So, after powering-off the cable-modem for that length of time, to allow the current DHCP-lease to expire, then it is possible that a new DHCP-request _might_ assign me a different IP-address. Maybe.  But, a simple "reboot" will renew the current IP-address.

[WRJZ]

Thanks @mdk . I thought that might have happened (reboot giving a new IP-address). But running a speed test, and  going to the What Is My IP site, tell me that I have the same address as before. As you say. I also have the same IPv4 number. (Not sure what this for, but I notice that the last digit is different for my iPad.) So what Shaw's POP server's spam filter is doing is still a mystery. I may have to switch to using Google Chrome and Gmail to send e-mail to my band group.

[mdk]

@WRJZ -- I notice that the last digit is different for my iPad.

I am not sure what you mean by that.

The "IPv4" protocol uses 32-bits of information, written as four "octets", e.g., "8.8.4.4".

Unfortunately, that means that there are "only" 4,294,967,295 unique IP-addresses on the Earth.

The "IPv6" protocol was defined to use many more than 32 bits, thus allowing every square inch on the Earth to have a unique IP-address. 

Is that what you mean by "4 versus 6" ?

On your home network, you probably have a maximum of 256 IPv4 addresses, but one IP-address is the "gateway" between your network and the Shaw network. So, your home network probably has a device using "192.168.0.2" and one using "192.168.0.3", namely only the final digit changes for each device. Is that what you mean?

[WRJZ]

@mdkYes the final number in the fourth 'octet' in the IPv4 address is different for each of my devices connected to my Shaw cable modem. For HP desktop computer (cable), iPad (wi-fi), iPhone (wi-fi), and Roku (wi-fi). The gateway appears to be 192.168.0.1. The final octets for my devices are 14, 13, 12, and 11.

I now know what IPv4 and IPv6 are. Asked my son-in-law yesterday. But why is the IP address I get using whatismyipaddress.com different? This tool says my IP address is 96.50.39.65. I thought this was my modem (gateway) address. On looking at the full headers of e-mails from myself I see this address enclosed in ( ) and the IPv4 number on the same "from" line.

Thanks very much for your responses. I have learned a lot. However, Shaw's spam detecting is still a mystery. I received an e-mail from Plex (a movie streaming service) today which was not tagged [spam]. Whereas the previous two were.

[mdk]

@WRJZ -- This tool says my IP address is 96.50.39.65. I thought this was my modem (gateway) address. 

Your cable-modem has a WAN (Wide Area Network) adapter, which gets an IP-address ("96.50.39.65 / S0106c8fb264854ca.pi.shawcable.net") from Shaw's DHCP-server, so that it has a "public" IP-address, reachable from any computer on the Internet.

Your cable-modem also acts as a "gateway" ("192.168.0.1") between your LAN (Local Area Network) computers/devices and the Internet.  The cable-modem's DHCP-server hands-out IP-addresses, in the format "192.168.0.xxx" to your computers/devices.