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Changing subnet mask has killed network

By tar12 ·
Had a new router (juniper) placed in service today which required all subnets on my network to be changed from 255.255.0.0 to 255.255.255.192.

With this I am on the machines changed to the new subnet mask able to access internet, but no networkfiles. On the machines were the subnet mask has not been changed I can access the network files, but have no internet capability or email (webmail source).

The PDC and BDC's (NT4) have both been changed to the new subnet and now cannot see each other.

Any advice?

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Changing subnet mask has killed network

by NetTek In reply to Changing subnet mask has ...

You do not say what network address you were given to use, but a subnet of 255.255.255.192 gives you 255 networks, each having 4 subnets, and each subnet having 63 nodes.

For example, if your network address is 192.198.1.0, and your subnet mask is 255.255.255.192, then you have the following subnets:
192.168.1.1-63
192.168.1.64-127
192.168.1.128-1**
192.168.1.192-254

These ranges are entirely different subnets when using a mask of 255.255.255.192. In other words, a machine with an address of 192.168.1.5 will not be able to see a machine with and address of 192.168.1.75. However, the router is designed to be able to send in receive to all of the subnets. That is why machines changed to the new subnet can see the Internet.

You need to put all of your machines in the same range. Either 1-63, 64-127, 128-1**, or 192-254.

Hope that makes sense.

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Changing subnet mask has killed network

by tar12 In reply to Changing subnet mask has ...

see comments above and perhaps you can advise with the additional info?

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Changing subnet mask has killed network

by tar12 In reply to Changing subnet mask has ...

I do have 3 subnet ranges and due to the amount of machines cannot put them all in one range. I also have 3 gateways. On the 1-63 subnet when I have changed those they access all - network, internet, etc. However, the machines on the other two subnets cannot access network or internet - take your choice. Could this be an issue with my gateways not talking to each other?

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Changing subnet mask has killed network

by NetTek In reply to Changing subnet mask has ...

I am confused, because you have not given much information. If it is not a subnetting issue, then it is some kind of routing issue.

How is your lan set up?
Are you using a proxy server?
What are your machines connected to? Are the hubs all connected, or does each subnet have its own seperate set of hubs?
How are your hubs connected to your router? Does your router have a single Internet port, and a single lan port? Or is your Juniper router also acting as a switch/router (i.e., does it have multiple lan ports)?

I am guessing that you have sets of hubs for each subnet that are seperate from each. Each set of hubs are connected to its own RJ45 lan connection on the router. Is this correct?

If so, I am guessing that because youwere given three subnets, and a subnet mask, that each lan port came preconfigured from your ISP. The routing should already be configured. The gateway for your machines should be the IP address of the lan port on the router for each seperate subnet. If the router came configured from the isp, do they not offer tech support?

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Changing subnet mask has killed network

by tar12 In reply to Changing subnet mask has ...

Poster rated this answer

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Changing subnet mask has killed network

by sgt_shultz In reply to Changing subnet mask has ...

sorry if this is dumb, but can't you just turn of dhcp server in the new router?

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Changing subnet mask has killed network

by tar12 In reply to Changing subnet mask has ...

we use static ip addressing

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Changing subnet mask has killed network

by D_V Ant In reply to Changing subnet mask has ...

If I am not mistaken, each subnet will need its own WINS server to enable you to browse the other subnets. This is straight from the Help files....

Windows Internet Name Service (WINS) provides a distributed database for registering and querying dynamic mappings of NetBIOS names for computers and groups used on your network. WINS maps NetBIOS names to IP addresses and was designed to solve the problems arising from NetBIOS name resolution in routed environments. WINS is the best choice for NetBIOS name resolution in routed networks that use NetBIOS over TCP/IP.

You will also want to ensure that NetBios over TCP/IP is enabled in your network properties.

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Changing subnet mask has killed network

by tar12 In reply to Changing subnet mask has ...

while not exactly right - putting the main server ip address into the win addresses of our workstations resolved the problem. thanks for the start into the right solution.

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Changing subnet mask has killed network

by pgm554 In reply to Changing subnet mask has ...

If you canot get out to the internet ,and your gateway ip address configured correctly,this definatly sounds like routing.

Can you ping your gateways?

Can you do a trace route to a site on the internet?(I.E. tracert www.microsoft.com) and seewhere the trace is timing out?

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