Default firewall rules on an Ethernet interface with DHCP ON of a Digi TransPort will block DHCP requests.

Introduction

This article will describe the required firewall rules to allow a Digi TransPort router to obtain an IP Address via DHCP on an Ethernet interface with firewall enabled.

Note: This article assumes a running configuration where ETH 0 is used, set to obtain an ip address from a DHCP server and firewall is enabled on this interface.

Warning: Enabling the firewall without proper configuration can cause access loss to the unit until it is rebooted.

Insert new rules

Navigate to Configuration - Security > Firewall

Under Action, click on Insert on the first line. (these 2 rules needs to be at the very top to be hit first)



Repeat this step 2 times to add the following 2 rules :

pass in break end on eth 0 from any port=67 to any port=68 inspect-state 
pass out break end on eth 0 from any port=68 to any port=67 inspect-state

Please Note: If you are using a different ethernet interface, for example a logical interface for Wifi, change the number to match accordingly (ie: ETH 1, ETH 2, ETH 12 etc..)



Click Save



Select the interface used. In this case ETH 0



Click Apply and Save configuration.




The ETH 0 interface should now obtain an IP address from the DHCP server.