Alias IP
Glenn Satchell
Glenn.Satchell at uniq.com.au
Mon Nov 20 14:37:07 UTC 2006
>X-Original-To: dhcp-users at webster.isc.org
>Date: Mon, 20 Nov 2006 15:11:34 +0100
>From: Zachár Balázs <zachar at direkt-kfki.hu>
>To: dhcp-users at isc.org
>Subject: Alias IP
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>Hello @list!
>
>I have the following problem:
>
>active/passive cluster with one virtual IP address...
>
>A node real IP: 192.168.1.2
>B node real IP: 192.168.1.3
>virtual common IP: 192.168.1.5
>
>So I have an alias IP address in my interface. The dhcp requests come to
>the alias IP (192.168.1.5) but the offers going out on the real
>interface IP (e.g. 192.168.1.2).
>Maybe the problem:
>If I give an IP with my real interface, and before the client would like
>to renew his IP address the cluster is failover, the dhcpd's IP address
>will change... But if I send the offers trough the alias interface, If
>the cluster fail over the IP address is still the same (the virtual IP)...
>
>Can I send the offers with my alias interface?
You might be able to use local-address,however there are some side effects.
local-address 192.168.1.5;
man dhcpd.conf
...
local-address address;
This statement causes the DHCP server to listen for DHCP
requests sent to the specified address, rather than
requests sent to all addresses. Since serving directly
attached DHCP clients implies that the server must respond
to requests sent to the all-ones IP address, this option
cannot be used if clients are on directly attached
networks...it is only realistically useful for a server
whose only clients are reached via unicasts, such as via
DHCP relay agents.
Note: This statement is only effective if the server was
compiled using the USE_SOCKETS #define statement, which is
default on a small number of operating systems, and must
be explicitly chosen at compile-time for all others. You
can be sure if your server is compiled with USE_SOCKETS if
you see lines of this format at startup:
Listening on Socket/eth0
Note also that since this bind()s all DHCP sockets to the
specified address, that only one address may be supported
in a daemon at a given time.
regards,
-glenn
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