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SNOM PNP on CS410 issues and troubleshooting tips


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We have recently upgaded 5 instock CS410's (BLACK) to the latest Firmware & MSP, and were planning an installation. The staff was having their buttocks kicked trying to get PNP operational. We engaged support (thanks) but the internal problems continued. The CS410 was configured with the PUBLIC IP and the internal LAN. Many hours passed, and PNP was non functional as configured. one thing that was said, in the process, was they saw PNP work with the CS410 provided DHCP services.


On a hunch,

Step 1.

assigned the LAN Interface a common local IP address (NO GATEWAY), and assigned a scope to the CS410 DHCP server. We also assigned another STATIC IP to the WAN interfce (NO GATEWAY). With the CS410 and a fresh SNOM phone plugged into a HUB, we were able to get PNP working. We were successful getting several more phones operational too.. NOTE, We also had a PC attached and have captured for reference purposes using WIRESHARK the entire PNP sequence.

Step 2.

We disabled the CS410 DHCP and using a simple DHCP server on the PC, we were able to duplicate our successes, and again capturing the entire sequence with wireshark.

Step 3.

We replaced the HUB with a few switches and confirmed the success.


The hunch is that whenever a GATEWAY IP is assigned to the CS410, this might be interfering with the PNP processes, by replying on the wrong interface. Remember the CS410 has three interfaces - LAN, WAN, and the 4 port analog gateway.


Our next step, is to assign a gateway and work towards making the PNP process fail. (It was consistently failing on all units)

We also want to make sure any routers that may have been involved in the earlier testing did not have UPNP enabled. This might interfere too..


We will know (with 100% assurance) what was causing this problem, and we will share the results, any LAB diagrams, traces and tips to anyone interested....


One possibility that might come of this is to not assign any gateways, but only use the ROUTES settings in the CS410. this might offer better security too.... Cheers

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Below is the configs and the route

Interestly after adding the gateway to the WAN IP, we began having PNP problems, the problem was compounded by a factory restart on a snom 320 test phone, so we are troubleshootingmore variables. The gateway was removed, and the route adjusted, but the PNP process appears to end when the phone makes a subscribe, and we see no reply from the PBX. (using a HUB to see all) Now going for Wireshark on the WAN port to see if these replies are going out the WAN port, and also adding routes to the PBXnSIP routes entry fields. (Perhaps that has become a requirement and will know more shortly.




This file was automatically generated by the IP PBX.

auto lo

iface lo inet loopback


auto eth0

iface eth0 inet static






auto eth1

iface eth1 inet static






auto eth2

iface eth2 inet static








Kernel IP routing table

Destination Gateway Genmask Flags Metric Ref Use Iface * U 0 0 0 eth2 * U 0 0 0 eth0 * U 0 0 0 eth1

default UG 0 0 0 eth2


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It seems we are back to seeing PNP work when the CS410 provides DHCP, and it appears to automatically setup and provide an option 66 setting to it's own IP address. We have read and assumed that PNP is now working using the ARP cache and resolve on the LAN and based on the latest snom docs, says an HTTP process improves the security. When things are working, we appear to be seeing the http process kick off after the sip registration requests happens to the localhost... When things are not working as expected (another device providing ip address only DHCP) we do not see that http processes after the subscribe message.. We did not see any traffic out the WAN port either..


I guess this leads to need for a good PNP Diagnostic Procedures.



To use option 66 or Not?

What needs to be verified to assure success? (no pnp devices on the lan, etc, other multicast activity.

What generated files can be deleted?

What files on the the PBX retain relevant information?

A basic PNP flow chart of what files are generated and when?

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Update, for those that are viewing this post.


Our hypothesis is, that we have upgraded a batch of CS410's from a V2 version... not likely capable of supporting multi-cast in the base OS.

We deployed the CS410 using the internal DHCP server, (it gave the option66) allowing the phones to be configured and regustered.

Turn on another DHCP server, the generated files still existed, and the new DHCP server had no option 66 tftp setting, but the phones had been already provisioned. Factory restart the phones, and they cannot register..

CANNOT JOIN THE MULTI-CAST traffic is in the LOG files....


Perhaps the BASE OS needs to be modified or reconfigured to support multi-cast. Looking now to verify Multicast is operational on the CS410.


Really don't want to force TFTP Option 66 onto smaller businesses best suited for the CS410. Check back later. Cheers

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Initial response from support appears to be confirming our hypothesis. Enabling Multicast in the OS, creating Multicast Routes appears not to be enough. Perhaps a MultiCast Debian package is in need of being installed to make MAC - PNP work on CS410's Oh the hours spent learning the hard way. Arg..... Now in a holding pattern for escalated paid support to help us address this problem. Cheers

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