dhcpd sending on the same IP it receives on
Glenn.Satchell at uniq.com.au
Wed Dec 12 12:43:54 UTC 2007
>Date: Tue, 11 Dec 2007 12:04:29 -0800
>From: Scott Baker <bakers at web-ster.com>
>To: dhcp-users at isc.org
>Subject: dhcpd sending on the same IP it receives on
>My DHCP server has multiple ips on its primary NIC. For example:
>eth0 = 18.104.22.168
>eth0:0 = 22.214.171.124
>I have my access equipment set to send DHCP relay to 126.96.36.199, but
>when the DHCP server responds it sends the response packet out via
>the 188.8.131.52 address since that is the primary address on that NIC.
>This causes my access equipment to drop the packet because the IP it
>sent to, and got the response from do not match.
>Is there way to tell the dhcpd daemon to send the packets outbound
>using the same IP (interface) that it received the packet on?
>The simple answer is to reverse the IPs so that 184.108.40.206 is the
>primary, but that's not really feasible since I have other services
>that require that 220.127.116.11 be the primary IP.
>Scott Baker - Canby Telcom
>RHCE - System Administrator - 503.266.8253
Have a look at the server-identifier statement, and maybe the
local-address statement. Between them they may do what you want.
In general though, the source address on an IP packet is a function of
the IP kernel driver and not the application. Virtual interfaces are
not like separate physical interfaces, the packets always go in and out
via eth0, it's just that it will accept packets with either IP
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