troubleshooting Question

subnet mask of

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ken021600Flag for Australia asked on
8 Comments1 Solution1274 ViewsLast Modified:

here's my question:
why i was assigned subnet mask of after dialing up to my local isp?

i mean, what's the point for my isp in assigning four 255s? why don't they assign a "common" one to me?

someone gave me the following explanation:
"When you dial to your ISP (regardless of the protocol), you establish a mini network between you and your ISP. You want any ip that is not on your local networks (if any) to be dealt though your ISP. If you have more than
one gateways, it makes sence to configure another mask, but if you have only one ISP's gateway to the world, the mask should be, so all ips by default are passed to your ISP. When you are off the internet, you don't have any gateway and a non-local ip is not matched, so you get "no network" error."

but i'm not sure if this is the correct answer coz:
it reads in my textbook that "for a specific host, the ip address of the router that is on the same segment as the host is known as the host's default gateway. all information that the host needs to send to segments
other than its own is routed through the default gateway. because a host and its default gateway are on the same segment, they have the same network id but different host IDs."

i was assigned an ip address of, my subnet mask is and my default gateway is

on the other hand, my ip address of was DYNAMICALLY assigned to me. how can this ip address be the same address as the default gateway?? i think the default gateway's address should be a fixed address.

so please give me some help.


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