Interconnection UCM6202 and UCM6102


I have an UCM6202 and UCM6102 interconnected. UCM6202 is configurated with 4 digit extensions and the UCM with 3 digit extensions. They have been working fine together for several years.

This week the provider of the UCM6202 have changed the static IP address. I have changed the address in both UCM’s in the peer VoIP trunk and in the security settings. What happens now is that the trunk will not register. Nothing else have been changed.

I have observed that it is not possible to ping the two UCM’s WAN addresses. Is this correct? Can you bar the UCM’s for answering ping requests? If so where?


Ip is public or not ?


Both have public static IP addresses


Despite the risk of exposing PBX systems to the public (not behind a firewall), did you change the public IP setting in the PBX Settings, SIP Settings, NAT so that it now has the new public IP?

If enabled, ICMP response will not be allowed for Ping request. The default
setting is disabled. To enable or disable it, click on the check box for the LAN or
WAN (UCM6200) interface.




The interconnection was configured correct, but it was impossible to ping the UCM6102 from the UCM6202 and the connection failed.

After nearly 2 month investigation my provider found out that my DSL line was missing an ARP proxy. Does anyone know why it is needed and what is an ARP proxy?

After adding the ARP proxy the issue was solved.