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I'm configuring my new ISP-provided Ubee DVW3201B Home Gateway. In doing this, I'd like to set up my own home network configuration which uses classless subnets. (i.e.: A subnet mask of in 172.16.x.x IP space.) However, I don't see any options in the LAN configuration which allow me to set a custom subnet mask. Is this a feature not available on this device? Does it default to classful subnet masks, or only use a /24 mask?

Sidenote: If anyone's found a manual for this thing, please do share!

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up vote 1 down vote accepted

Classful networking was already long gone by the time the web took off in the mid-1990's. By the time home gateways became a thing (as broadband ISPs came online in the late 1990's), they all did CIDR subnetting.

Most home gateways that don't show the subnet mask on the LAN side default to a /24, because that's more than enough host address space for a home network, and the vendor didn't want to waste resources supporting more hosts than that.

To confirm, see what subnet mask your gateway's DHCP server serves your your DHCP clients.

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This home gateway does show the subnet mask, but does not allow changing it. I've confirmed that it's stuck at /24 by changing the IP range to a different class. Thanks for the info. – Iszi Mar 13 '12 at 4:11

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