DHCP Auto Deployment

[TimWardlaw]

Hello,

I am having my first goes at configuring automatic config and software deployments to SG250-26 switches.  One area I am not sure how to get around is this.

In our environment we have a multitude of the these SG250 switches deployed that connect back to our core via trunk links.  I would like to be able to replace devices as needed with 'zero touch'.  Meaning, I plug the mac of the new switch in the DHCP scope, it boots up grabs it's image and config and off to the races.  However, since my uplinks are configured as trunks I am having a hard time getting DHCP to traverse these links at boot since, obviously, they are not configured as trunks yet.  I tried setting the native vlan on the trunks to that of the management subnet which the DHCP server would be on, but without any luck.

Can any of you provide some feedback as to an approach I can take?  I can get it all working fine when the device connects to an access port, as expected.  It is just the fact that the links are trunks and I cant get that DHCP request to go up it.

Thanks for your time.

[Jaderson Pessoa]

Well..

Could you share your configuration of your core and your swich sg250?

[Georg Pauwen]

Hello,

just a thought: what if you configure the uplink ports as access ports, and in the configuration file (that is then downloaded), have these ports configured as trunk ports?

[TimWardlaw · Accepted solution]

So I was able to make it work my modifying the trunk ports.  The core is a netgear M4300-52G, don't ask..., and the trunks were originally configured as 'general' ports.  After setting the to trunk the dhcp requests then went up the native vlan as expected.

However, I am not seeing the SG250 try to process anything from the dhcp offer.  It gets an IP put doesn't seem to do anything with the option 125 or 67.  I've run a capture on the dhcp server and can see that the offer is being sent with the right options, I just cant see on the switch what it's doing with it.  Things don't have a console port so I cant even watch it.

Any suggestions or experience with getting this to work?  I am following the example here:

https://www.cisco.com/c/en/us/support/docs/smb/switches/cisco-small-business-200-series-smart-switches/smb5328-configure-option-125-on-a-server-to-allow-dynamic-host-confi.html

I'm beginning to wonder if it's the relay on these netgear cores that are the problem at this point.

[TimWardlaw]

Ok, progress.  These devices, which isn't stated clearly in the manual, have auto config and auto image disabled by default.  You must use PnP and option 43 in DHCP.  Which isn't covered in that section of the manual.  Let's try this again...

[paul driver]

Hello

confirm what links are trunks  - the uplink from each switch or the ports the hosts are connecting to?