Questions

Subnetting

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Subnetting

janstan10
We currently have a subnet of 255.255.255.0. We are adding several new employees over the summer which will put our computer/device count to well over 300 (All under the same roof). We do not have DHCP installed on any servers or allowing DHCP to be handed out. To connect to our network you have to use a static ip address. There is a sonicwall firewall that is plugged into our ISP modem and from there the sonicwall is plugged into a cisco SG 200-50 gigabit smart switch. We actually have 3 of these smart switches that we use throughout the building.
My question is how to add either another subnet or should I go to VLANS since the smart switches support VLAN? I need to add more IP address asap but I'm not very experienced in subnetting or VLANS. What would be the best practice?
I understand that changing my subnet to say 255.255.255.248 will increase my range but where to do I change this so this is being handed out to the devices and computers?

Any guidance would be very much appreciated! :-)
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    Slayer_

    Lower is more essentially.


    "My question is how to add either another subnet or should I go to VLANS since the smart switches support VLAN?"
    Sounds like you just want to switch from class C to class B. Cmiller is correct, I would follow his advice.

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    0 Votes
    Alec Lerg

    We have a SonicWall also on our network, we could use it as DHCP server, but we have another server doing that.

    Here are some great videos about subnetting, that may help you.
    You can find the subnet that you need at the minute 13 in the second link.

    http://www.youtube.com/watch?v=DCQLphkatqE
    http://www.youtube.com/watch?v=ltYpMZBIhhE
    http://www.youtube.com/watch?v=pngt5mX7glU

    You can also find other great videos related to networking there, good luck!

    By the way thanks to Jeremy Cioara for those great videos.

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    0 Votes
    govind_avinashraj

    If the subnet mask is changed from 255.255.255.0 to 255.255.248.0, you will definitely increase the range. However you have mentioned that all existing users have static IP. In that case you would have to change the mask in every machine which will be a lot of work. Maybe you should start segregating the users and create multiple vlans. IP addresses can be static/dynamic.

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    2 Votes
    cmiller5400

    Changing your subnet to 255.255.255.248 would give you only Six hosts per network.

    You need to go the other way, 255.255.248.0 would then give you 2046 Hosts per network. Or you could even do a 255.255.252.0 which would give you 1022 hosts per network, all depends on what you want to do with your network and how many possible class B subnets you will need in the future.

    Yes VLANS would work as well, but you would then need to add routing to the mix... I don't know if that particular model switch supports layer 3 routing but if not, I believe that you would then need a router involved to connect the vlans.

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    0 Votes
    info

    ...it sounds like it's out of your depth. Have you given any thought to having a network consultant come in and lay out a plan on how to sort things out?

    It also will depend a bit on your physical layout. It was easy for me, as I have two buildings that are connected by a high-speed wireless bridge. Two 255.255.255.0 subnets between them, with a WatchGuard firewall also working as a router, and done. I'll be going to VLANs at some point, although it makes things a bit trickier. If a switch dies, you have to have it's replacement configured on installation rather than just throwing one in and getting it power.

  • +
    0 Votes
    Slayer_

    Lower is more essentially.


    "My question is how to add either another subnet or should I go to VLANS since the smart switches support VLAN?"
    Sounds like you just want to switch from class C to class B. Cmiller is correct, I would follow his advice.

    +
    0 Votes
    Alec Lerg

    We have a SonicWall also on our network, we could use it as DHCP server, but we have another server doing that.

    Here are some great videos about subnetting, that may help you.
    You can find the subnet that you need at the minute 13 in the second link.

    http://www.youtube.com/watch?v=DCQLphkatqE
    http://www.youtube.com/watch?v=ltYpMZBIhhE
    http://www.youtube.com/watch?v=pngt5mX7glU

    You can also find other great videos related to networking there, good luck!

    By the way thanks to Jeremy Cioara for those great videos.

    +
    0 Votes
    govind_avinashraj

    If the subnet mask is changed from 255.255.255.0 to 255.255.248.0, you will definitely increase the range. However you have mentioned that all existing users have static IP. In that case you would have to change the mask in every machine which will be a lot of work. Maybe you should start segregating the users and create multiple vlans. IP addresses can be static/dynamic.

    +
    2 Votes
    cmiller5400

    Changing your subnet to 255.255.255.248 would give you only Six hosts per network.

    You need to go the other way, 255.255.248.0 would then give you 2046 Hosts per network. Or you could even do a 255.255.252.0 which would give you 1022 hosts per network, all depends on what you want to do with your network and how many possible class B subnets you will need in the future.

    Yes VLANS would work as well, but you would then need to add routing to the mix... I don't know if that particular model switch supports layer 3 routing but if not, I believe that you would then need a router involved to connect the vlans.

    +
    0 Votes
    info

    ...it sounds like it's out of your depth. Have you given any thought to having a network consultant come in and lay out a plan on how to sort things out?

    It also will depend a bit on your physical layout. It was easy for me, as I have two buildings that are connected by a high-speed wireless bridge. Two 255.255.255.0 subnets between them, with a WatchGuard firewall also working as a router, and done. I'll be going to VLANs at some point, although it makes things a bit trickier. If a switch dies, you have to have it's replacement configured on installation rather than just throwing one in and getting it power.