Ericsson HM4x0 Reference Manual page 231

--> firewall add portfilter pf2 ext-int udp 53 53
outbound
Example three – using a provided protocol, application or service
The following example allows SMTP (Simple Mail Transfer Protocol) packets
inbound and outbound between the internal interface to the DMZ interface.
This is a popular protocol that is provided by the Firewall. You do not need to
specify the portnumber – the Firewall does this for you.
Then we can add the portfilter to it:
--> firewall add portfilter pf3 dmz-int smtp both
10.7.5 See also
See the Well Known Port Numbers section of RFC 1700 for a list of port
numbers and protocols for particular services.
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