DHCP Broadcast flag
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I have a couple of wireless devices that are sending bootp broadcast flags on their DHCP requests.
Whenever this happens and I capture the traffic at the pfsense interface the DHCPD never sends a response.
Is there a way for it to respond to these requests through broadcast?
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@bigjohns97
"Ignore BOOTP queries" checked in the DHCP server settings? -
@viragomann No it isn't, would that solve this problem?
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@bigjohns97
No for sure, that could be the reason for not replying. -
@viragomann Appreciate the reply, this seems to be something going on with the DHCP server on the pfsense not responding to DHCP requests when the broadcast flag is set. This is causing a couple of my IoT devices to not be able to get an IP from DHCP.
https://www.ietf.org/rfc/rfc2131.txt
" To work around some clients that cannot accept IP unicast datagrams
before the TCP/IP software is configured as discussed in the previous
paragraph, DHCP uses the 'flags' field [21]. The leftmost bit is
defined as the BROADCAST (B) flag. The semantics of this flag are
discussed in section 4.1 of this document. The remaining bits of the
flags field are reserved for future use. They MUST be set to zero by
clients and ignored by servers and relay agents. Figure 2 gives the
format of the 'flags' field."I have noticed that whenever this flag is set PfSense will not respond with an dhcpack. I have been doing the captures using the client MAC address which should see all traffic.
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Looks like moving to a port based filter on the tcpdump is now showing the proper response so I don't think this is a PfSense issue.