Can router DHCP scope be pumped back into a WAN?

Erwin Krisch
Erwin Krisch used Ask the Experts™
on
In the diagram below, as far as I understand it, as long as the WAN cables are not connected to the LAN ports of the routers, A and B, the DHCP addresses broadcasted of these routers will not be pumped into the WAN.  Only if the WAN cables are connected to the router’s LAN ports can such a thing happen.  Is this correct?
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Most Valuable Expert 2011
Commented:
DHCP cannot cross a router on its own.  It depends on broadcast from the Clients, and broadcasts won't cross routers.

A real router can have DHCP Helper Addrresses,...but I suspect that these are "home-user-NAT-boxes" and not real routers (due to the address ranges in the diagram).   Even if they were real routers,...you also need a real DHCP Service that is capable of Scope Options, Server-Level Options and the ability to run multiple Scopes (one per subnet).

Most Valuable Expert 2011
Commented:
Plugging the WAN cable into the LAN ports would cause more damage than just the DHCP situation.  Yes if you did that then a client plugged in anywhere that was set to dynamic addressing would get an IP Config from whatever DHCP "service" answered first (first-come-first-serve).

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