[SGVLUG] DSL: static or faster?

[Emerson, Tom (*IC)]

-----Original Message----- Of Claude Felizardo

I'm hesitant to swap out the old modem for several reasons:  If I cycle power, am I going to lose my static?  ... Will a new modem let me specify static?  I believe my modem is set up as a bridge so no PPP over anything.  No login.  It just works.  Which makes me wonder what prevents just anyone from "grabbing" "my" IP if my modem is offline?
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First off, if you have been assigned a static address, then no, cycling power won't lose the number - take a look at how DHCP servers are configured - generally they are given an address range to "manage" - if there was one or more "static" addresses within that range, how would the DHCP server know to avoid them when handing out addresses?

Secondly, your address is, or should be, part of a regular class "C" address - the first three octets are the network address, the last is the device address.  If you have a 5-static deal, this last octet has probably been subnetted down to 8 devices - however "all zeroes" and "all ones" within a subnet are not valid, and the "router" usually takes an address within the "subnet", leaving you with 5 viable addresses within the subnet.

For example, if your "subnet" is 129.0.0.64, you will likely be told to use addresses ending in .65 through .69, and that your "gateway" address is .70 - .64 and .71 are not "valid" addresses, and .72 begins the next subnet block.

[actually, .71 would be the "broadcast" address]

For a single-IP setup, you and 252 of your closest neighbors w/static addresses share the same basic class-C network.  My address, for example, is 207.105.40.84, and my "gateway" address is 207.105.40.254 - I suspect that the device configured with the .254 address is in the CO, so if someone wanted to "steal" your address, they'd have to be wired to this router, and if they were, they would already have their own static address to begin with.

Tom