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DHCP Management Across a Diversified Network?
ET Admin writes "I work for a small Wireless ISP, where we are deploying new network hardware to allow for growth and contain broadcast traffic. All routing/switching equipment is Cisco. We use Linux stand-alone boxes and VMs (running on Win 2003 boxes). We have decided on a hybrid VLAN layout where we have certain VLANs limited by location, and other VLANs that are global across the network. And I want DHCP served across it all. Does anyone have experience with IPAM software that handles multiple DHCP servers? Our network is small so spending a couple grand is overkill at this point. Any recomendations to help me decide between serving DHCP from the Nix boxes, or from the Cisco gear? Knowing that a single DHCP server will handle from 100-500 hosts."
Seriously, do not use the Cisco gear to handle the DHCP. There are several ways to handle this, either have a system with an interface on all the networks, or setup your Cisco gear to forward the HDCP requests to the one subnet that does have your system.
With using Unix/Linux you can setup failover servers so that if one does not respond, the other will take over the requests and that way you will not lose DHCP across your entire network due to hardware/software issues on a single system. Go read up on dhcpd, it is not too difficult to understand, and is really probably your best low cost solution.
We were all warned a long time ago that MS products sucked, remember the Magic 8 Ball said, "Outlook not so good"
You need to use DHCP snooping to block rogue DHCP servers and block packets with forged MAC addresses on untrusted interfaces
You need IP source guard to block forced IP addresses on untrusted interfaces
Otherwise, you are at risk of DOS and/or compromise from malicious users, and at risk of instability and insanity caused by users who plug a rogue DHCP server (even something as simple as the LAN side of a Linksys gateway) into your gear.