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Subnet change...need help

By ditamaddon ·
I have a situation in which my company (A) rides of the backbone of another company (B). My network consists of Server2003, Exchange 5.5, OWA, file/applications servers, and 35 clients that run 2000/XP. Half of my workstations are in another building connected by a fiber WAN. Company B has informed me that they will need to take away the current subnet of the other bldg and place them on a new one. I am concerned because I do not fully understand how this subnet change will effect the following:

1. How will this effect access to mail?
2. How will this effect access to files/application servers?
3. How or what will I be able to use to help them remotely?
4. How will this affect printer access?

Any help would be greatly appreciated.

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by Jellimonsta In reply to Subnet change...need help

If these two buildings are connected by a WAN, you will need to change the IP/subnet range on your local router to point to the newly configured IP/subnet range of the remote equipment. Why do they need to change the subnet range? Or change your IP scheme?

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by ditamaddon In reply to WAN

thanks for the response...Company B has people moving in on the upstairs location (we are on the bottom floor) and they are basically booting me off to accomodate them. I'm not familiar at all w/TCP/IP and not sure how to connect to subnets to insure that they play together nice. So your basically sayin that as long as my local router has the new subnet...they will play nice and I will still be able to keep file/app servers where they are?

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by Jellimonsta In reply to Jellimonsta

Is this move a logical or physical one? Networking has 2 concepts, logical and physical. The physical would be the cat5 cables, routers and nodes. The logical would be the network infrastructure type (i.e TCP/IP and subnet class). In your initial question, you mentioned they are changing your subnet? Subnet classes are a way to determine which part of an IP address is the 'network' address and which part is the 'host' address. For instance IP address with a subnet mask of is considered class C. Therefore the first 3 octets (.) are reserved for the network address.

Check out and

Both of these sites are free and are great explanations of TCP/IP and Subnetting respectively. If you are simply facing a physical move and you still have connectivity to either your resident infrastructure or Internet/ leased line (if it is indeed a WAN) then there may not be any configuration necessary.

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by ditamaddon In reply to Physical?


thanks again for all your advice...i really appreciate it...I will be reading the links you gave so I can get a better idea.


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Your routers will

by jdclyde In reply to Subnet change...need help

handle it all for you.

Asides from changing the addresses on the systems, the rest should be transperent to you and your users. (do you manage the routers?)

All your servers know is current network and gateway.

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by Jellimonsta In reply to Your routers will

Assuming they are not using static routes. Unless they are simply changing the internal space and using NAT. I guess there are a lot of assumptions one could make here.

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static routes

by ditamaddon In reply to Assuming

when you say static routes do you mean static ip addresses?

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Kind of

by Jellimonsta In reply to static routes

Static routes would be entered on a network device to dictate which route traffic takes to get to the desired destination. This would be used if you are not using any network protocols like OSPF or EIGRP. You would need static addressed network routers in order to use static routes, but you would not need static IP addresses for network nodes.

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It won't be all that bad...

by mhasf In reply to Subnet change...need help

If you are using WINS and/or DNS, then your workstations will know exactly where to go. We have two buildings, each with around 40 Workstations and they are on separate subnets. No big deal!

The only problem that will come up is if they put another mail server on the other subnet. I have set this up too. What I did was to create an internal MX record in DNS which points to the 'sort-of' foreign server. That fixes the problem of your mail server (and theirs) of trying to resolve the other mail server's address using the 'outside' FQN. For example, if the outside FQN is, then just create a new MX record in your DNS pointing to the internal address. Works like a champ! If you are not using DNS, then you may have to add entries to your HOSTS file for those servers.

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not that bad

by ditamaddon In reply to It won't be all that bad. ...


Thanks for your reply! I had at one point set up a DNS/DHCP server here on the network..this changed as we needed static IP's to connect to an external server that was IP specific. I need to read some links that another member has sent me so that i can get a bit more familiar with TCP/IP...thanks again for your input!

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