[c-nsp] Cisco 2960G not passing DHCP

Alexandre Guimaraes alexandre.guimaraes at ascenty.com
Sun Oct 22 22:38:20 EDT 2017

Sound stupid, I know.

Once upon a time.... still stupid, I know.

Using the same 2960G, the problem was at Layer1 mismatch with some type of PDU or security doors controllers, some of these equipments don’t have port negotiation, so you have to set manually and check if the cable had the correct configuration T568A-B


Em 22 de out de 2017, à(s) 20:25, Curtis Piehler <cpiehler2 at gmail.com<mailto:cpiehler2 at gmail.com>> escreveu:
I'm racking my brains out on this yet it seems so simple unless I am
encountering a bug.

I have several host devices connected to the following switch,
Firewalls/PDUs, etc...:
Switch Ports Model              SW Version            SW Image

------ ----- -----              ----------            ----------

*    1 48    WS-C2960G-48TC-L   12.2(55)SE10          C2960-LANBASEK9-M

This switch sits down stream from a 3560G which uplinks to a firewall
(Router on a stick).  The problem I am encountering is that the devices
connected downstream of the 2960G are not receiving DHCP from the 3560G
switch or firewall.  Of course I have one DHCP at a time but to test
different devices that can serve out DHCP.  What's odd is that I have the
same exact model PDU connected to the 3560G and it obtains DHCP without

The devices downstream of the 2960G do not yield any MAC address.  I have
done all sorts of DHCP debugging and nothing comes up from the devices.  I
even tried moving the DHCP server down to the 2960G and I see no activity.
Statically assigning IPs to devices work no problem.

The PDUs are Raritan factory defaulted so when the port is shut/no shut
they are designed to get DHCP.  The firewall is a Fortinet with the
interface set to obtain DHCP.

Unfortunately I can not get a traffic sniffer on this switch but I'm
wondering if anyone has had this issue before or heard of this.

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