Core issue
By default, inbound traffic to the PIX Firewall does not allow you to Telnet to or ping the inside interface.
Resolution
To access the inside interface of the PIX through Telnet (over an IPSec tunnel), management access on the inside interface is needed. These rights must include access to the remote networks in the local PIX Telnet commands.
To configure this access, issue the management-access inside command on the PIX. The management-access mgmt_if command helps to define an internal management interface with the IP address of the PIX interface specified.