Option 82 problem

[Александр Сандецкий]

Hi, SImon.

Thank you for detailed description.

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. It more manageable and more simple for configuration. I will try it.

пт, 17 апр. 2020 г. в 21:04, Simon Hobson <dhcp1 at thehobsons.co.uk>:

> Александр Сандецкий <alexander.sandetsky at gmail.com> wrote:
>
> > I have a problem with option 82 configuration.
>
> Actually, I suspect the thing you do not have a problem with is Option 82 !
>
> > I have managed switch with IP 10.10.0.38 (managed VLAN 100). There is
> additional VLANs configured for clients: VLAN 3000 and 3010. There is
> option 82 and DHCP relay configured on the switch.
> >
> > I have DHCP server placed in VLAN 3000 with IP 172.18.0.101
> >
> > I want to DHCP server serves the VLAN 3010 (and other) on per-VLAN basis.
>
> Does the ROUTER serving the VLANs have IP addresses in those VLANs ? Do
> you even have routing set up yet ? Note that a MANAGED SWITCH is not the
> same thing as a ROUTER - though you can get devices (typically called
> something like "Layer 3 switch") that include both functions. Without a
> router (or routing function built into the switch), what the VLAN config
> gives you is a stack of separate LANs - almost as though you had a stack of
> switches, one per LAN.
> Before trying to sort out the DHCP - make sure you have the routing
> sorted. If you manually configure a client on the 3010 VLAN (I assume this
> will be an access port) in the 172.18.10.0/24, can it ping the server at
> 172.18.0.101 ? If not, fix that first; if it can, use traceroute and check
> that it is in fact routing via a router and not accidentally going direct
> (there are ways of making the cross-subnet traffic work other than routing
> it).
>
> Summary : You will need a router configured with interfaces in VLAN 3000
> and VLAN 3010, with IPs in the 172.18.0.0/24 and 172.18.10.0/24 subnets
> respectively. it will probably also have an interface on VLAN 100 in subnet
> 10.10.0.0/?? to allow you access to manage the switch.
> When you have this working, and you configure the DHCP Relay agent, then
> things should "just work".
>
> > The part of dhcpd.conf
> >
> > class "VLAN3010" {
> >         match if binary-to-ascii(10, 8, "", substring(option
> agent.circuit-id, 2, 2)) = "3010"
> >     }
> >
> >
> > subnet 172.18.10.0 netmask 255.255.255.0 {
> >     option routers  172.18.0.1;
> >
> >     pool {
> >             range 172.18.10.51 172.18.10.250;
> >             allow members of "VLAN3010";
> >     }
> > }
>
> That is not how you serve VLANs. For the VLAN stated, all you need is :
> subnet 172.18.10.0 netmask 255.255.255.0 {
>     option routers  172.18.0.1;
>
>     pool {
>             range 172.18.10.51 172.18.10.250;
>     }
> }
> When requests come from a relay agent in the 172.18.10.0/24 subnet, it
> will automagically select the right subnet and hand out a suitable address.
> Note that the relay agent does not have to be in the router, but it MUST
> have an IP address in the network it's serving - it's just that this is
> usually most conveniently done as an integral part of the routing.
>
> > The server receives request as
> > DHCPDISCOVER from 2c:27:d7:b1:a2:85 via 10.10.0.38: network 10.10.0.0/24:
> no free leases
>
> This suggests to me that you have not correctly configured your switch and
> router. For that client, you should NOT see a request coming from
> 10.10.0.0/24 subnet.
>
> Simon
>
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-- 

С Уважением,
Сандецкий Александр
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