Can't Ping ARP Issue?

[Ben Duff]

Hi,

We have a building alarm panel with a network adapter, this is connected to a 3750E switch. It was working just fine and now suddenly we can't connect to it.

Ping fails and an arp lookup returns 'incomplete', adding a static arp entry also makes no difference.

If we directly connect a laptop to the alarm panel bypassing the switch we can ping and it works. If we connect the two devices (laptop, alarm panel) through a cheap unmanaged switch it works.

I suspect the network adapter on the alarm panel is faulty, no changes were made prior to this, we've tried cables, rebooting the switch, different ports etc. We have another alarm panel and this one is fine.

As it works when directly connecting or using an unmanaged switch is there a way to configure the 3750 in a similar matter so we can get it working?

Thanks
Ben

[marce1000]

 - Chances are very slim. that this is related to the 3750, I still suspect the network adapter of the panel , even it worked on another device (perhaps it has problems, with a long distance signal due to hardware problem). Replace it's network adapter; have cabling test do between this panel and the switch.

M.

[mattjones03]

Hi,

Could you share the sanitised interface configuration connecting to the endpoint device?

Here are some common causes for ‘incomplete’ ARP;

1. Cabling/NIC Issue

2. Network switching loop

3. Mis-configured VLAN on the interface connecting to the endpoint device

[Ben Duff]

Thanks, I suspect it's the network adapter on the alarm panel at fault, it's strange that it works if directly connected or connected through a cheap unmanaged switch. It was working correctly prior to this. Cables/ports have been swapped.

Switchport config below

switchport access vlan 2
switchport mode access
switchport port-security
switchport port-security aging time 2
switchport port-security violation restrict
switchport port-security aging type inactivity
macro description cisco-desktop
spanning-tree portfast
spanning-tree bpduguard enable

Have tried without the port-security and makes no difference. If we do an arp against the IP we get incomplete, setting a static arp entry has no effect.

Thanks
Ben

[mattjones03]

Hi,

Which variant of the Cisco Small Business switch are you running?

[paul driver]

Hello

With what you have stated, it doesn't seem to suggest the problem is with the NIC on that panel it seem more like the vlan assignment on the switchport of the 3750

Is vlan 2 in the same subnet as the NIC panel address range?
Does the nic panel have a default-gateway?

From the host you trying to ping from, is this on the same subnet as the nic panel?
Is the 3750 performing inter-vlan routing and if so is routing enabled ?

res

Paul

res
Paul

[Ben Duff]

Hi,

It was working correctly until just recently when it suddenly stopped, it was being worked on by a technician. vlan assignment is correct, all hosts are in the same subnet.

The reason I mention ARP is that it's not registering. Does a cheap unmanaged switch behave differently than the Cisco when it comes to mac addresses? Are we able to change the configuration of the Cisco so it behaves like the unmanaged switch?

Thanks
Ben

[marce1000]

 - Is the connected interface on the 3750 up and running (show interface status  x/y) ; also check for CRC errors in the output of this command , or other interface errors if any. If needed clear the counters of the interface and re-connect the device, check if any CRC and or other errors appear if network activity is attempted.

M.

[Ben Duff]

Interface appears fine, no errors. It's something to do with the mac not being added to the table, suspect the adapter is faulty but wondering if there's a way to work around this, have tried a static arp with no success.

Thanks
Ben

[Richard Burts]

I appreciate your telling us that the interface appears fine. But can you post the output of show interface status and of show interface so that we can see for ourselves what it is saying?

HTH

Rick