If you are configuring a home network or SOHO network, determining your egress filtering requirements begins with compiling a list of services to which you need access (this might include such services as DNS, SMTP, POP and/or IMAP, NTP, and HTTP/HTTPS). If you are configuring a corporate network, you probably want to begin by consulting your organization's security policy. You may also want to consult with those in charge of network security and perhaps other stakeholders within the organization.
You should make a list of remote servers that services running on your network have to access, and allow them through the filter. For example, if you are running a DNS server, it will undoubtedly have to communicate ...
