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78xx Phones & HP/3Com Switches

Has anyone seen or heard of any issues with the 78xx phones and HP/3Com switches? (This is on 5500 & 4400 models)

We're seeing some weird issues whereby a 79xx or 69xx phone works fine on the HP switch, but in the same port a 78xx doesn't. Doing a WireShark, you see the 78xx phone DHCP & then continuously ARP the default router. After a while it repeats this DHCP/ARP cycle. It never gets any further in the boot process.


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78xx Phones & HP/3Com Switches

Hi Gordon,

I ran in to a similar issue to this with 7911s on HP switches.

The issue was that these phones needed CDP to discover their voice vlan id.

Hp switch that was being used could not run CDP

Manually configurung the voice vlan on the phones resolved the issue.

Reading the data sheet and admin guide for the 78XX I see they use CDP too.


ADMIN---> set the ADMIN VLAN to your voice vlan number --> apply

Worth a try

You may need to investigate using LLDP to autiomate this.

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Regards, Alex. Please rate useful posts.

78xx Phones & HP/3Com Switches

Been there. Done that. No dice :-(

One of my difficulties is that HP's port mirroring doesn't include the VLAN headers, so you can't check the packets are on the correct VLAN :-/

Thanks anyway,


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78xx Phones & HP/3Com Switches

Hi Gordon,

Please refer below links and see if any one helps you.

Nishant Savalia

Regards, Nishant Savalia

78xx Phones & HP/3Com Switches

Thanks for the links, but I don't think they apply in this case. As I said, 79xx & 69xx phones are working fine, so the basic VLANs, LLDP-MED, etc are all setup correctly. There's something funky going on with the 78xx phones. (And I'm confident that it's not an OUI issue)


Please rate all helpful posts.