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

SpiderX spiderx at spiderx.dp.ua
Thu Sep 15 13:25:44 BST 2011


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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