Solution:
When you enable the WAN firewall for "inbound", all traffic including ICMP (ping requests)are blocked from getting through the WAN from the outside world until you start adding firewall entries to allow specific traffic to get through. Here is an example on how to add a firewall entry to allow ICMP (ping) requests.
Note: The protocol port number for ICMP is '1'.
Before you can enable the WAN Firewall you must have configured a "Remote Site" configuration in your router.
=============================================================
Select the following menu options:
Configuration / Applications set-up / Firewall Set-up / WAN Firewall set-up
You will be prompted to enter the name of your Remote Site configuration to be associated with this firewall entry.
Change the "Firewall" option to "inbound".
Select the "Edit firewall entry" menu.
You will be prompted to enter a Firewall filter id (from 1 to 128). For example, if this is the first firewall entry enter "1".
Change the Firewall entries as shown:
1. Destination addr [all] - Destination IP address of frame
2. Destination mask [none] - Network mask for dest address
3. Source address [all] - Source IP address of frame
4. Source mask [none] - Network mask for source address
5. Protocol type [1] - Allow specific protocol types
6. Source port [0] [65535] - Source port range to allow
7. Destination port [0] [65535] - Destination port range to
8. Description "Manual entry" - Describe the entry
9. Entry direction [inbound] - Direction this entry applies to
Press the = key.
Select the "Save Configuration" option.
Select "Diagnostics" option, then select "Soft reset".