[Dnsmasq-discuss] DHCP Relay, assign address from other vlan, with no dhcp listening on it

Michael Rack michael.rack at rsm-freilassing.de
Thu Sep 15 16:05:58 BST 2011


Why is schema 2 safe you one ip per interface? You need a ip-address for 
routing, so that should be that ip-address dnsmasq is listing on. Or is 
your router not the same device where your dnsmasq is running on?

Have your interfaces a /30 Network assigned? Or are they all bind on a 
bridged interface on your Unix-Router with only one ip-address-range /24 
or something else?

Liebe Grüße aus Freilassing,

Michael Rack
RSM Freilassing
-- 
RSM Freilassing                 Tel.: +49 8654 607110
Nocksteinstr. 13                Fax.: +49 8654 670438
D-83395 Freilassing            www.rsm-freilassing.de


Am 15.09.2011 14:25, schrieb SpiderX:
> On Wed, Sep 14, 2011 at 5:42 PM, richardvoigt at gmail.com
> <richardvoigt at gmail.com>  wrote:
>>> I don't agree. Dnsmasq is a great software, I use it for years in a
>>> small environment.
>>> In bigger networks usage of l2 switches is necessary, and as Michael,
>>> I dont know too any l2 switch that supports any dhcp-related RFC,
>>> except 3046.
>>> There are not some many unix dhcp software that can be used with l2
>>> switches, dnsmasq could be one of it. And, as I said earlier, it
>>> should be.
>>> Solution with taking preference circuit-id and remote-id over
>>> sub-option 5 can be implemented as switch, documented with warning in
>>> manual, not enabled by default in example config.
>> dnsmasq works great in conjunction with L2 switches.  Usually you put
>> the dnsmasq node on a VLAN trunk port, that way it sees requests from
>> all circuits, along with the VLAN tag.  I'm not sure why you've chosen
>> to relay to a non-trunk port instead.
> Let's take a look on situation. There is a network with access type
> vlan per user or vlan per switch (not fundamentally),
> which builded on globally routed ip addresses (I mean "white ips", not
> 10.0.0.0/8, etc.)
>
> Sheme 1
> client — broadcast — l2 switch's port 1 — broadcast — server (dhcp
> listening on interface with utilization of one ip in subnet)
> client — broadcast — l2 switch's port 2 — broadcast — server (dhcp
> listening on interface with utilization of one ip in subnet)
> ..............
> client — broadcast — l2 switch's port 24 — broadcast — server (dhcp
> listening on interface with utilization of one ip in subnet)
>
> Sheme 2
> client — broadcast — l2 switch's port 1 — unicast — server (dhcp
> listening on interface with utilization of one ip in subnet)
> client — broadcast — l2 switch's port 2 — unicast — server (dhcp
> listening on interface with utilization of one ip in subnet)
> .............
> client — broadcast — l2 switch's port 24 — unicast — server (dhcp
> listening on interface with utilization of one ip in subnet)
> Dhcp is listening on one interface and utilizes one ip address. This
> ip/interface is not directly accessible by clients.
>
> Which of these schemes is more safer and more reliable?
> Which of these schemes is easier to maintain?
> Which scheme is more economically viable? (I don't lose one ip per
> interface with dhcp server listening on it. One ip = one client.)
> Dnsmasq can be used in scheme 1, but not in scheme 2.
>
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