Cisco 3524XL DHCP acting strange: spanning tree?

By robo_dev ·
The Cisco switch is connected to a generic 2Wire DHCP server. Everything works great, except....

I am installing some Ademco 8132 alarm keypads that are basically single-board computers that use DHCP. When plugged into the Cisco switch, they get no address.

Plug them into anything else, and they're happy as a clam.

For example, if I plug a my trusty netgear four port switch into a port on the Cisco, and plug the keypads into the netgear switch,the devices get an IP just fine that way. So DHCP is working...somehow the Cisco is having some heartburn at layer 2??

Are there any magic Cisco settings to look at?

The Cisco is set to factory defaults, so there is only one VLAN. I believe Spanning Tree is turned on by default.

Do I maybe need to disable spanning tree? (the network topology is flat). Any other weird settings to fiddle with?

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well it was a thought eh?

by CG IT In reply to POE
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by NetMan1958 In reply to Good thought

If the problem is not resolved by setting the speed and duplex manually, it could be a spanning-tree issue. Look at the config for the affected interfaces and see if they have port-fast enabled. If they don't you can enable it like so:
Switch1(config-if)#switchport mode access
Switch1(config-if)#spanning-tree portfast

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Thanks, will try that

by robo_dev In reply to Also

Cisco complexity = job security :)

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Answer: Duplex issue

by robo_dev In reply to Cisco 3524XL DHCP acting ...

(forehead slap)

Logged and set the port to 10MBS Full Duplex and it's now purring like a kitten. Apparently the alarm keypad auto negotiated to 10/half, which did not work so well.

On the Ademco 8132 keypad the ethernet connection is used for news/sports/weather and email, but not actual alarm stuff.

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yeah I've got a couple of devices that are 10baseT

by CG IT In reply to Answer: Duplex issue

and that's what they do as well. half duplex. Switch is full so mismatch.

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