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Calculating subnet mask

Posted on 2009-05-04
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Last Modified: 2012-05-06
Hello,

I would like to link my network to the one next door. Currently, he has the address range 192.168.30.1-254 and I have the address range 192.168.0.1-254.

What subnet mask would we need to use to allow these two networks to "talk" to each other? I have tried reading up on subnets but I am struggling to understand it.

Thanks,
Jonathan
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Question by:acsell
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by:Pete Long
Pete Long earned 31 total points
ID: 24293675
Hello acsell,

These are both Class C, networks (have a 255.255.255.0 subnet mask) to make then "SEE" Each other you would need a router between the networks with a route to each network

Regards,

PeteLong
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by:anvanster
anvanster earned 31 total points
ID: 24293681
225.225.224.0
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by:stany0
stany0 earned 31 total points
ID: 24293714
network portion of ip addresses must be the same. This addresses are class C, then the first three octets must be the same. The better way is to add second IP address to you NIC, which is in the network of your neighbor, or ask your friend to migrate to 192.168.0.0 network or you can migrate yours to 192.168.30.0. You can use Lan calculator from this page (http://lantricks.com/download/), and things will become clear.
To 'talk' each other the different networks, traffic between them must be flow trough a gateway router, server.
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woolmilkporc earned 32 total points
ID: 24294032
anvanster - nearly perfect, let me just correct your typos  ;-)
255.255.224.0
which means -

first usable address - 192.168.0.1
last usable address -  192.168.31.254
thus no router needed.
wmp
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by:acsell
ID: 24294042
Thank you for your replies. So, for what you have said, I can either do the following-

Put a router in-between the networks to route the traffic - I would not know how to configure this though.
Add a second IP address
Change them all to use 192.168.0.x or 1092.168.0.30
Change them to use 255.255.224.0 as a subnet mask.

From what I understand, 255.255.224.0 is a class B subnet mask. If I changed the subnet to this but kept the same class C IP addresses, would there be any downside?




(I don't know if it makes a difference but we actually have a server in-between the two networks with a wireless connection to my network and a wired connection to my friends network, these two connections have then been bridged on the server.)
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by:woolmilkporc
ID: 24294128
Don't worry about classes - we now have CIDR (and, if you insist. it's still class C anyway, as the above mask constructs 32 class C networks containing 8192 addresses each).
Please read this -
http://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing
You'll have to adjust the netmask of your server, of course.  
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by:woolmilkporc
ID: 24294207
Oops, made a typo myself - forget the 'each' above! The phrase was planned to look quite different when I began to write it down.
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by:acsell
ID: 31577491
Thanks for that information. I will change all of the subnets then.

Thank you all for your help.
Jonathan
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