IP phone registration issues - default gateway

[Kane Smith]

Hi guys,

I have attached a diagram of my lab environment. CCM v10.5, a DSL router and a Cisco 2811 on the same LAN. The Cisco 2811 has a PoE power supply and an Etherswitch module powering a 9951, 8945, 7821 and a 7970 on a voice VLAN.

I spent 2 days trying to work out why none of these phones would register. No firewall, routing all OK, DHCP addresses issued OK, correct device pack on the CCM, phone firmware all SIP and at compatible versions, deleted ITL cert, erased network & security settings, factory defaulted the phones, etc. I can ping the phones from any device on the CCM LAN, but not a single IP phone would register. Auto registering or manual phone config made no difference.

Eventually I moved the 8945 to the CCM VLAN and reconfigured the IP addressing for this network and it registered straight away. I repeated this for the other phones and they all registered successfully. I moved the phones back to the voice VLAN and reconfigured the IP addressing. Now they no longer register. I verified that connectivity is all good.

Phone status message reported errors getting the config file: <Hostname>.cnf.xml and VPN error: VPN not configured.

Then I thought of the CCM's default gateway. Historically, it was pointing at the DSL router. The DSL router had a static route for the 10.X.X.X network pointing back to the 2811. When I changed the CCM's default gateway to point to the 2811 directly, all phones registered within seconds!

If you've followed this far, any idea what caused the issue?

Is this redirect via another device, i.e. the DSL router not supported?

Is it something to do with MTU?

[HARIS_HUSSAIN]

I think ADSL router is not routing traffic between Phone and CUCM.

Try to connect a PC Back of Phone and do a packet capture.

User below procedure

https://supportforums.cisco.com/document/44741/collecting-packet-capture-cisco-ip-phone

Thanks

Haris

[Kane Smith]

Thanks Haris,

I have taken a Wireshark trace (attached) from the working scenario.

Which lines show that the config file is being requested and supplied?

[Dennis Mink]

Personally I would point everything to the 2811 and put an ip route 0.0.0.0 0.0.0.0 to your DSL, much easier.

Please rate if useful

[Kane Smith]

Hi Dennis,

Good solution, but the issue is that I have signed up to the KYOTO agreement and therefore the 2811 and several other heavy duty servers are only powered on during lab sessions :-).