Where do you use IP Helper Addresses, FW Router or L3 Switch

By lmalhoit Contributor ·
I'm trying to decide if there is a best way to implement IP Helper Addresses/DHCP relays. We have a stack of Dell Powerconnect L3 switches, but the routing is not currently turned on. We also have a Juniper SSG320 that is capable of doing DHCP relays. Where is the best place to configure them? Obviously, the routing will need to be turned on if I decide on the L3 switches.

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Where ever IP needs help

by robo_dev In reply to Where do you use IP Helpe ...

Assuming that your FW Router is connected to the Internet, and not a corporate WAN, then the helper addresses would be needed on the L3 switches. Not sure where your SSG320 is installed in your network.

Helper addresses are used to forward things that are typically broadcast protocols (e.g. ARP, DHCP, NetBios) across subnets, which normally does not happen in a routed network.

Typically these are needed in an enterprise WAN when DHCP servers may be too far away. In this scenario, they would be needed on the edge router/firewall at each remote site.

On the local network with several VLANs, helper addresses are used so that dumb protocols like Microsoft Networking can work...otherwise nothing works if your domain controller or WINS server is on another subnet.

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