DHCP over LAG fails on SG500X

[toni.zeitler]

Hi,

we have a SG500X-24 and try to configure clients by DHCP. All  clients are connected to static LAGs, an external DHCP server is  connected to a single port. What we see now is that the DHCP server  receives DHCP requests and correctly answers with DHCP offers to the  correct MAC addresses, but these offers never reach the clients. How can  this be fixed?

If we connect a client without LAG or to just one single port of a  LAG, DHCP works as expected. If the second port is connected to the LAG  (and actually becomes a LAG), it fails. We did not yet configure VLANs,  we kept the default setting with the default management VLAN, all  ports/LAGs set to UP. The plan is to create two VLANs with two DHCP  servers - if we get it working.

We narrowed it down to these basic steps:

(1) reset switch to factory settings

(2) connect DHCP server and client - DHCP works as expected

(3) create a LAG with two ports and connect client to both - DHCP fails (see first paragraph)

We also tried with the internal DHCP server of the switch, without success yet. Firmware is the latest one (1.3.0.62).

Best regards,

Toni

[Tom Watts]

Hi Toni, can you test with the different load balance mechanisms? Are you using a static LAG or LACP?

-Tom
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[toni.zeitler]

Hi Tom,

we use static LAGs. Meanwhile, after another software update of the client, we got them working with the switch-internal DHCP server. The external one still does not work (same behavior as described above). So maybe it is the clients' fault. On the other hand, DHCP over LAG works if we connect such a client directly to an Intel server adapter, create a static LAG, and run a DHCP server on the machine.

We can try with the load balance mechanisms - maybe it helps. Thank you!

Best regards,

Toni