I recently got access to a Motorola SBV5121E cablemodem. No, I'm not switching to cable Internet access at the moment as ziggo still doesn't offer fixed IPv4 addresses or IPv6 at all on consumer connections. But it was interesting to give the cable modem a try. If I am correct, this is the 'previous' generation cable modem. The maximum speed on the ethernet interface is 100 Megabit where Ziggo now offers subscriptions up to 120 Megabit. When not connected to the cable network, the modem runs a small DHCP server for IPv4 which gives out 192.168.100.x addresses. The management interface is reachable via http://192.168.100.1/, username admin password motorola. When I connect the RF interface to the tv cable, it gets a link. In the management interface I see Downstream frequency 186000000 Hz (186 MHz) with QAM256 modulation. The upstream frequency is 36000000 Hz (36 MHz) and the interface lists QPSK, 32QAM and 64QAM modulation, I guess the fastest one with a reasonable error-rate is chosen. Downstream speed is listed as 55.616 Megabit and upstream speed as 30.720 Megabit. Interesting to see quadrature amplitude modulation (QAM) used here, just like in the DVB standards. I guess this is the best way to fit bits in a broadcast channel. Connected to the ziggo cable and running tcpdump shows arp traffic originating from ziggo routers. Trying to cause traffic to ziggo IPv4 addresses from the outside shows arp for only one IPv4 address I tried, not for lots of others. Which means either all those clients are active (needing no ARP try needed) or one IPv4 address to the next being active in separate broadcast domains. I also ran tcpdump with the modem starting up disconnected at the cable side. Absolutely no packet comes out on the ethernet interface. First time I tried to get an IPv4 address from cable using DHCP while connected it gave me a IPv4 address from the 198.18.0.0/15 range, a range "reserved for benchmark tests of network interconnect devices". When I tried to visit any website I got redirected to www.ziggo-activatie.nl at 172.25.4.6 / 172.25.38.6 (which is in RFC1918 space). This website identifies itself as activation site for the provider, asking for a provisioning code and password. I guess the activation site will link cable mac and customer account in the databases at the cable operator side. A scan of the assigned network (a /24 out of 198.18.0.0/15) shows several IPs in use all having the same MAC address 00:30:B8:xx:xx:xx (RiverDelta Networks). A search for RiverDelta Networks shows it is a maker of cable modem termination systems and has been acquired by motorola. When I tried it again it with the same cable modem it doesn't give me an IPv4 address at all. An interesting change. Update: Later another Motorola SBV5121E cablemodem found its way to me. Trying this modem gave me an IPv4 address via DHCP again and a new try at the activation server so I could look up certain things described in this item and update it.