From: Bob Smith (ccnet101@nmccentral.com)
Date: Mon Nov 29 2004 - 15:17:06 GMT-3
As long as the router/dhcp server is in the same VLAN, those hosts will get
a response, however, if its a different subnet or network, just remember
helper address...
----- Original Message -----
From: "ccie2be" <ccie2be@nyc.rr.com>
To: "Group Study" <ccielab@groupstudy.com>
Sent: Monday, November 29, 2004 10:00 AM
Subject: DHCP and the 3550
> Hi guys,
>
> I would like to just confirm something regarding the above.
>
> Assume a router's ethernet interface is connected to a 3550 port which is
> vlan
> X along with a bunch of hosts.
>
> Also, the router is configured as dhcp server for the hosts in vlan X.
>
> Am I correct in thinking that nothing related to dhcp must be configured
> on
> the 3550?
>
> The way I understand it, when a host in vlan X powers up and sees it needs
> an
> ip address, it will broadcast a dhcp request. The 3550, when it gets that
> broadcast, will flood the broadcast out all ports in vlan X. Thus, the
> router
> acting as a dhcp server will get the broadcast dhcp request. After
> getting
> the request, the router will respond using the source mac address of the
> request as the destination mac address.
>
> When the 3550 gets the response, it will forward it to the host.
>
> In other words, the default behavior of the 3550 is such that nothing
> related
> to dhcp (such as dhcp snooping, dhcp relay, etc) is required for dhcp to
> work
> properly in the above scenario.
>
> I'd hate to lose points for dhcp on the lab if I correctly configure it on
> the
> router and forget to configure some stupid little thing on the 3550.
>
> TIA, Tim
>
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