Option 82 problem

[Александр Сандецкий]

Basic network services topology assumes that DHCP server exist in every
network segment. In every VLAN in my case. It can be separate servers in
network segments or single server with network interfaces gor every
network. Or every VLAN configured on the server. This is a simple and clear
idea. But in some cases it's not good (need to configure lot of vlans for
ex.). But DHCP service offers the relaying technology. With combination of
Option 82 it's common practice to setup single server with single network
interface for DHCP. Option 82 can be used to classify clients by the switch
(agent IP or MAC), by the switch port, by the vlan, etc.

Relaying assumes the dhcp query comes not from original device and original
network segment but from some managed switch where client connected. With
some additional information for identifying client and swithc.

My idea is to not to configure every vlan on the server.

сб, 18 апр. 2020 г., 00:08 Simon Hobson <dhcp1 at thehobsons.co.uk>:

> Александр Сандецкий <alexander.sandetsky at gmail.com> wrote:
>
> > Actually I do not fully understand how it works. My hardware vendor say
> me that Option 82 MUST be configured on the edge (client access ) switches
> but you says (as I can understand) that it must be configured somewhere on
> the "main" (core) ROUTER, not every switch. Your concept more prefferable
> for me.
>
> I suspect something has been lost in translation because you DO NOT NEED
> OPTION82 AT ALL for DHCP to work. You do not need it on edge switches, you
> do not need it on a core switch.
>
> To clarify a bit ...
> treat each VLAN as if it was a separate LAN - conceptually think of a VLAN
> enabled switch as a stack of "simple" switches. At some point, you need a
> router to link those networks together - but instead of needing a router
> with lots of ports (one per network), when using VLANs you can combine all
> the VLANs down one cable with the ports on each end in trunk mode.
> Once you have the basics working (any device can reach any other device,
> firewall/access rules permitting, then you can consider DHCP. The only
> requirement there is that the DHCP server has a connection to at least one
> network (it can directly connect to more than one), and any network not
> directly connected to the DHCP server needs a Relay Agent to pick-up
> broadcasts from the clients and forward them to the server (and relay
> replies back again).
>
> Simon
>
>
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