Member Avatar for owaithaka

hi, we replaced a 1900 series switch with a 2960 switch but now we have a michine that cannot connect to the LAN. when u plug in the cable its connecting to a 1gbps network yet we oprate on a 100mbps network. ip assigining is done by the DHCP. Tried connecting a different machine to the point its said limited connectivity. tried pinging the switch from the different machine its saying destination host unreachable.

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  • Latest Post Latest Post by Capt_Kirk

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Building on and , here is a focused set of switch-side diagnostics and remediation steps for a Cisco 2960 that complement the host-side checks already suggested. These look for configuration features on the new switch (VLAN/trunking, port-security, STP, DHCP-snooping) that commonly break host reachability even when the link LED shows up.

Run these commands from the switch and note the outputs for the problem interface (replace Gi1/0/X with the real port):

show interface status
show interfaces GigabitEthernet1/0/X
show running-config interface GigabitEthernet1/0/X
show mac address-table interface GigabitEthernet1/0/X
show vlan brief
show interfaces trunk
show port-security interface GigabitEthernet1/0/X
show errdisable recovery
show logging
show spanning-tree interface GigabitEthernet1/0/X detail
show ip dhcp snooping
show ip dhcp snooping binding

How to read common results and next steps:

  • If the interface is in err-disabled, inspect show logging to see the cause (port-security, BPDU-guard, link-flap). To clear a port-security lock use clear port-security dynamic interface <iface> and then shutdown/no shutdown on the interface to bring it back. Consider adjusting port-security limits if violations are legitimate.
  • If the MAC table shows no client MAC on that port but the interface is up, check whether the port is assigned to the correct VLAN and whether that VLAN is allowed across uplinks (show interfaces trunk). A host on an access VLAN that isn’t carried to the DHCP/gateway will appear unreachable.
  • If DHCP snooping is enabled, ensure uplinks are trusted or client ports are correctly configured; otherwise DHCP replies get dropped and hosts won’t get addresses.
  • If STP shows the port blocked, verify topology, portfast settings for edge ports, and any BPDU-guard behavior.

Capture console/logs while plugging a client in; that often gives the exact reason (errdisable cause or security violation). These switch-side checks usually locate configuration blockers that survive a chassis swap.

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Member Avatar for DimaYasny

does the machine work on another port of the switch?
if it does - you must have configured the specific port for 1G connectivity, or just non-negotiation.
if it doesn't, check the port settings on the switch, but try to play around with the NIC settings on the machine - try with other duplex settings, speed negotiation etc. or even try with a different NIC

and yes, the basics - are the cables alright?

Member Avatar for Capt_Kirk

First thing I would do is check the local area connection in the control panel. Does it show you are pulling an IP address? Was the machine configured for a static IP? If it was configured with a static IP it would show as connected, but not get any conectivity.

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