Frame Tagging

Steven Carr sjcarr at
Thu Aug 15 08:59:40 UTC 2013

On 15 August 2013 08:11, Simon Hobson <simon at> wrote:
> Not having used it on a switch, hmm I feel a test coming on ..., does it actually remove the original packet from the wire ? Ie, does it intercept and block the original broadcast packet before it gets forwarded by the switching fabric ?
> I'm thinking that since the primary function of the relay agent is to relay requests to an off-segment server, in the basic case there'd be no need to actually remove the original packet - only capture and relay it. If that is the case (and it's only guesswork from me), then just adding a relay agent function to the switch won't be sufficient, you'd also need to disconnect the server from that segment/VLAN or compile the server to not use raw packets.

Correct, typically when you deploy this type of DHCP the DHCP server
"lives" in it's own network, or does in some cases provide DHCP to the
local subnet, but the remote subnets use IP helpers to forward the
initial DHCP broadcast requests. If you had an IP helper on the same
subnet then the DHCP server would see the same request twice, first
from broadcast, second via IP helper.


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