DHCP and Route Priority

[Bob Harold]

On Fri, Jun 2, 2017 at 3:36 PM, Bill Shirley <
bill at c3po.polymerindustries.biz> wrote:

> Classless static routes are used by an OS because they're more specific:
> # ------------------------------------------------------------
> ------------------
> option classless-static-routes          code 121 = array of unsigned
> integer 8; # for Windows Vista and other non Windows DHCP clients
> option classless-static-routes-ms       code 249 = array of unsigned
> integer 8; # for Windows 2000 and XP clients
> # ------------------------------------------------------------
> ------------------
>
> subnet 10.0.0.0 netmask 255.0.0.0 {
>     option routers              10.96.0.12;
> .
> .
>     option classless-static-routes
>         24,192,168,1,           10,96,0,9,      # lan1 192.168.1.0/24 gw
> 10.96.0.9
>         23,192,168,64,          10,96,0,9,      # site #2 192.168.64.0/23
>         32,192,168,5,2,         10,96,0,76;     # serverB
> 192.168.5.2/32
>
>     option classless-static-routes-ms
>         24,192,168,1,           10,96,0,9,      # lan1 192.168.1.0/24 gw
> 10.96.0.9
>         23,192,168,64,          10,96,0,9,      # site #2 192.168.64.0/23
>         32,192,168,5,2,         10,96,0,76;     # serverB
> 192.168.5.2/32
>
> Not all dhcp clients are capable of utilizing them though.
>
> Bill
>
> On 6/2/2017 2:31 AM, Pavel Zhukov wrote:
>
> "David G." <lightman at fastmail.fm> <lightman at fastmail.fm> writes:
>
>
> Hi,
>
> How can I communicate the priority of routes and routers via DHCP? I'm
> trying to get computers on my network to use another router for a
> specific subnet but everything is just going to the default gateway. I'm
> using DHCP option 121 to set the route.
>
> Hi,
> Which OS are you using? Classless routes should be set by dhclient script which is
> vendor specific.
>
> Thanks!
>
>
>
Try adding this to your DHCP configuration:

on commit {
  log(info,
    concat("REQUEST-LIST",
      " IP=",binary-to-ascii(10,8,".",leased-address),
      " MAC=",binary-to-ascii(16,8,":",hardware),
      " req-list=",binary-to-ascii(10,8,",",option
dhcp-parameter-request-list)
    )
  );
}

Each time a lease is issued, it will log the list of DHCP options that the
client requested.  If the client does not request code 121 or 249, then the
server will not send them, because the client does not expect them and
probably won't know what to do with them.

-- 
Bob Harold
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