Mac OS X Server 10.6 Snow Leopard: DNS and Network Services
Illustration by John Hersey

Troubleshooting client-side firewall issues


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Mac OS X Server 10.6 Snow Leopard: DNS and Network Services

with Sean Colins

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Video: Troubleshooting client-side firewall issues

Since I showed you how to configure the application firewall and turn it on, I think it's only fair that I show you where its log file is and how to read it. So, to do that, we're going to go into Terminal once again and we're just going to type open /var/log/alf.log. When that opens, it'll open up in console and we'll see here that we have our application firewall log. One of the last things that it mentions is that it's creating the appfirewall.log.
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Watch the Online Video Course Mac OS X Server 10.6 Snow Leopard: DNS and Network Services
2h 4m Intermediate Jul 16, 2010

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In Mac OS X Server 10.6 Snow Leopard: DNS and Network Services, instructor Sean Colins introduces the networking services available in Snow Leopard Server. This course covers setting up a DNS server to provide network resources, using firewalls to protect systems against intrusion and to route traffic, using DHCP to automatically configure network settings for computers when they join a network, and accessing a network securely via a remote VPN (virtual private network) connection. Exercise files accompany the course.

Topics include:
  • Deploying, troubleshooting, and understanding OS X 10.6 DNS server
  • Understanding and configuring OS X and OS X Server-based firewalls
  • Fixing server- and client-side firewalls
  • Configuring and troubleshooting DHCP
  • Setting up and troubleshooting a VPN server
Subjects:
Business Developer IT
Software:
Mac OS X Server
Author:
Sean Colins

Troubleshooting client-side firewall issues

Since I showed you how to configure the application firewall and turn it on, I think it's only fair that I show you where its log file is and how to read it. So, to do that, we're going to go into Terminal once again and we're just going to type open /var/log/alf.log. When that opens, it'll open up in console and we'll see here that we have our application firewall log. One of the last things that it mentions is that it's creating the appfirewall.log.

So, we're going to go down here and look at the rest of what it lists. So, when you read that log, it's simply going to tell you about allowed or denied traffic associated with an application name and where the traffic came from. If the log is telling you that it's denying traffic you didn't intend, take a look at that application firewall configuration again to make sure it's what you wanted. If your system is blocked from administering the server still at this point, you're going to want to go back to your server using the local connection that we recommended in the Understanding This Title movie.

Check your computer group to make sure that the address is the same as the static IP address that you have configured here on your client system. You want to be sure that you have full access at this point. Go ahead and do that now, as you're going to need your server to be fully accessible from at least the client computer from this point forward in the title. In some organizations, there are entire groups of people dedicated to configuring and monitoring the organization's firewall. If you're in a small organization or maybe it's just you, it's still worthwhile to open up the logs especially on your server and in Console, filter on the word Deny, and scan through it quickly for large chunks of deny activity.

You can do that easily by going into your server, just as we are here on the client, and just typing the word deny here and what will result will be anything that was denied traffic. If someone is trying to break into your server, it's better to find out about it before they succeed, than to react to the break-in once it's already happened.

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