Digi APPLICATION NOTE 34 - Manual (Page 10)

10
inspect-state – monitor the pings for echo replies and allow them back in
oos
10 t=3 c=3 d=3 – if 3 consecutive pings fail, deactivate PPP 1 and start recovery procedures after
10 seconds. This 10 second timer could be increased (by editing the firewall rule) to prevent the Digi
Transport from switching rapdily between PPP 1 and PPP 4 in the case where PPP 1 works intermitantly.
This “oos
10 ” can be thought of as a de-bounce timer in the context of this application note.
r=ping,
10 , 5 rd=1 dt=1 – during recovery, test the link every 10 seconds with a ping, allow 5
seconds for the response to each ping, if the recovery fails deactivate the interface and deactivate the link
before trying again
Rule 2 then allows all other traffic through.
For a more detailed explanation of the above firewall keywords refer to the Sar/OS reference manual
“ftp://ftp1.digi.com/support/documentation/Digi Transport and Sarian User Guide.pdf”
Finally turn the firewall on for PPP 1 to activate the ICMP monitoring and recovery.
Configuration - Interfaces > PPP > PPP 0 - 4 > PPP 1 > Standard
Parameter Setting Description
Firewall ON Switches the firewall on for this interface
Click OK
2.5 Save configuration
Save your configuration as the power up configuration.
Administration - Save configuration
Click OK
Reboot the Digi Transport router (or deactivate PPP 1) so the PPP changes take effect.