netmask is 255.255.0.0, but should be 255.255.255.0

Question

netmask is 255.255.0.0, but should be 255.255.255.0

I have two PowerBooks which connect to the Internet via a cable modem and a WiFi base station. One of them stopped connecting to the Internet, although it still connects to the base station, and I noticed that the subnet mask is 255.255.0.0, but should be 255.255.255.0, however I cannot see how to make it use 255.255.255.0.

Can anyone suggest what I can do to restore the computer to normal operation? Thanks in advance.

PowerBook G4 1GHz 512 SDRAM 1MB L3 Mac OS X (10.4.8)

Posted on Jan 5, 2007 11:30 AM

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Answer 1

BDAqua

Level 10

250,259 points

Jan 5, 2007 1:46 PM in response to Peter Blackburn

It might be the Automatic Location, it seems to revert to past settings sometimes, even deleted ones... I'd make a New Location just for this connection... in fact for any connection.

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Answer 2

Jan 5, 2007 12:52 PM in response to BDAqua

The computer that works has an IP that matches the router IP, which is also shown in System preferences: 88.157.222.106 and 88.157.222.254 respectively. The computer not working has another IP altogether. Where would this have come from? The DHCP cannot be working properly. It does not show a router IP.

It is strange, as it was working OK on another home connection, all the time on automatic, using DHCP, and worked at my home fine before that.

Manually setting an IP won't work, as the wireless base is giving out IP via DHCP. I want to keep it automatic for convenience, and in any case, as you say, there is clearly something wrong that needs to be fixed.

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Answer 3

BDAqua

Level 10

250,259 points

Jan 5, 2007 12:05 PM in response to Peter Blackburn

That in itself shouldn't stop you connecting, it should actually allow you to connect to 256 times as much!

Copy down the other 2 values, (IP & Router), then beside Configure IPv4, set it to Manual, fill in all values.

But I think there's other problems.

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Answer 4

BDAqua

Level 10

250,259 points

Jan 5, 2007 3:59 PM in response to Peter Blackburn

DHCP uses the IP in the Router position to send a request for the next open IP number, the Router then, (if set to do so), sends back it's next open IP number to use.

The Router IP can only be set by using Manual, or perhaps "Joining a Network".

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Answer 5

Jan 5, 2007 3:10 PM in response to BDAqua

Created new location, but same thing happened.

It is not getting the IP at all. How does DHCP work to do this? That's where I think I need to look.

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