[j-nsp] Firewall filter for locally generated packets

Ian MacKinnon ian.mackinnon at lumison.net
Thu Mar 27 12:33:13 EDT 2008

Hi all,

I am doing some work with PXE-booting of servers and using bootp helpers 
to get to the dhcp server.

All working fine so far.

However the dhcp response back to the server appears to be coming from 
the local interface directly, and our standard firewalling is dropping it.

I can open the firewall to allow all udp 67/68 packets through,but I 
would rather limit it.

Now I could add the local ip address to the rule, but have have a 
standard set of rules we apply to all interfaces, so if there is some 
way of specifying allow locally generated packets through that would be 

we have an interface with an ip address like
In syslog we see
Mar 27 16:05:41 my-router-01/my-router-01 /kernel: %FIREWALL-6-FW: 
.local..0    R  udp    67    68

ie the interface name is .local..0 and the source is

Our firewall rule then looks like :-
term permit_bootp_install {
     from {
         source-address {
         protocol udp;
         destination-port [ 67 68 ];

But rather than use the source-address what can I use for locally 
generated packets?



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