Problem: Mac OS 10.5.8 – Firewall blocking incoming DHCP data

Symptom:
1. Airport is unable to get IP when switching from one network to another.
2. Firewall log shows: Deny configd data in from XXX.XXX.XXX.XXX:67 uid = 0 proto=17

Solution: Manually add configd to firewall configuration exception list to allow incoming connections
1. System Preference -> Security -> Firewall
2. select ‘set access for specific services and applications’
3. click ‘+’
4. press ‘command’ + ‘shift’ + g
5. type /usr/sbin -> click Go -> select configd -> click Add

You may want to add following system process in the exception list too:

mDNSResponder – DNSResponder — Multicast and Unicast DNS daemon More details: http://developer.apple.com/networking/bonjour/faq.html

racoon — IKE (ISAKMP/Oakley) key management daemon