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dhayes's avatar
dhayes
Follower
Sep 19, 2017

2 DHCP server same subnet

Hello All.  I have what is likely to be a simple question (I think).  We have a corporate network in one building and it has a mask of 255.255.0.0 because there are alot of devices on that network.  Addresses for devices there are 192.168.110.x, 192.168.120.x and 192.168.130.x.  On that network there is a windows DHCP server serving up IP addresses for those devices in 192.168.110.x for now.  Basically everything is VLAN1 at this location.  

 

Now they just purchased a new building a and have a point to point fibre BRIDGE (NOT Routed) between the locations.  Basically, it is 192.168.140.x for devices at that location.  Now because it is bridged it will broadcast DHCP packets and pick up an IP address from the main location in the 192.168.110.x network which is really completely valid for 255.255.0.0 mask.  However, I would like devices at this new building to have DHCP assign IP's of 192.168.140.x so this would involve another DHCP server.  And, I would rather not use the DHCP server at the corporate location just in case the fibre goes down.  I would like to have the DHCP local to the new building.  

 

Now I could handle this via VLAN's but I would rather not bother messing with VLAN's due to constraints of other devices on the 192.168.140.x network that are statically assigned.

 

So with these netgears is it possible to create another DHCP server on 192.168.140.x on the S3300-52X switch with all the info above?  And, prevent devices at the main corporate location from getting IP's from the new DHCP server (Possible DHCP Snooping?)?  All without messing with VLAN's? 


Thanks for any info and have a great day!

Dave

1 Reply

  • Hey,

    Thanks for the thorough explanation :)

    The "real" answer is of course to segment via VLANs. I understand you are not in a position to do so at the moment. What you can do instead is use DHCP snooping, as you mentioned yourself. Basically, configure the switch in the new building to use DHCP snooping and then only trust the port where the DHCP server, for building 2, is. That will essentially discard DHCP replies on any other port.

    In the long term, the company should consider making plans to implement VLANs. With large networks, broadcast will eventually become an issue. Something to maybe plan for!


    Cheers

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