General Networking/Lan/Wan/IP Address

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Question
Goodevening,

We have servers and PC that use to have the same subnets (e.g 192.16.1.23.....) and now we recently using a different subnet in all employees computers (see example below)

Before change, employee1 pc is set to STATIC - 192.16.1.23
After change,  employee1 pc is set to DHCP - 192.17.1.55
and so on......

All our servers remain untouched.  I noticed that I am not able to ping a network printer by ipaddress but the rest of the printers works.  Also 3 of my mapped network (used server name) drives were no longer accessible so I had to re-map it using IPAddress instead. I am confused as to why I cannot ping a network printer and cannot use use servername to map a drive.

Any help would be gladly appreciated.

Thanks

Answer
Hi Jan,

I've changed your question to public so that it may help others as well, and hope that you don't mind.

From what I can tell, your situation is actually pretty simple.  You created, in effect, a new network, but there isn't a way for the 2 networks to talk to each other.  This is what we call ROUTING - to allow one subnet (or network) to communicate with each other.  For each network, there must be a device like a router (sometimes in the server) that allows 192.16.1.0 to talk with 192.17.1.0.  That would typically be the Gateway for each network.  Thing is that this doesn't always Scale very well since it forces a SINGLE device with a mere 100 or 1000 (gigabit) connection to be a choke point between the two networks.  Even if the gateway/router DOES have a Gigabit PORT - it doesn't necessarily mean that it can actually route traffic (packets) at anywhere even close to that Interface/port speed!

I have to assume that you added the new subnet because you were running out of addresses, with just the one?  If that's not the case, and you have a total of 254 DEVICES (pcs, laptops, printers, servers, etc), then you probably should just stick with the one old subnet and move everything back onto 192.16.1.0/24 (/24 means a subnet mask of 255.255.255.0 - the /24 is a "bitmask notation" for the same thing.  Do you really NEED more than 254 devices?  That's usually quite ample for most smaller companies.

If you merely need more than 254, then instead of setting up routing, etc (and risking a bottleneck that could really affect performance) - you could just reconfigure your entire network so that you have more addresses available and keep everyone on the same one subnet/network.  For instance, a /23 give you 508 usable addresses.  Instead of using a subnet mask of 255.255.255.0 - everyone uses 255.255.254.0.  That is the same thing as /23.  The change from 255 to 254 in the 3rd octet "adds a bit" valued at another network space.

Oh - and the servername / ip problem is because the PCs that are trying to connect to servernames need some device to TRANSLATE that name into the IP - this is typically done using DNS (or older ways like WINS or even just dumb flat files like LMHOSTS on the PCs.  That is a pain to manage.  It's best to just have a nice simple flat network with one router/gateway - and increase the size of your network by changing the SUBNET MASK - so that you've got the room that you need (if 254 addresses won't do the trick).

Note: Going bigger than /23 is probably not advisable - too much "broadcast" chatter on one network.  But I'm guessing that even if you do need "more than 254" that it isn't too much more.

On related matters - try and ensure that every switch connects back to one core switch with a full Gigabit link, and keep all servers, routers, on the one "core" switch.  If possible don't "daisy chain" switches together.  I know that isn't always do-able - running more cables and such - it's just good practice.

I hope this helps!  Please ask follow-ups if you need!

J.  

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Specialist in leveraging technology toward fulfilling a customer's business objectives: enhancing revenues and giving them a competitive advantage in the marketplace.

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