FWBuilder DNS Object Run Time - when exactly does it resolve the DNS name?

Posted by Jakobud on Server Fault See other posts from Server Fault or by Jakobud
Published on 2010-04-19T15:36:26Z Indexed on 2010/04/19 15:44 UTC
Read the original article Hit count: 309

Filed under:

fwbuilder

|

iptables

In Firewall Builder, when you use the DNS Object and set it to run time, when exactly does the firewall (iptables in our case) actually resolve the DNS name?

Is it whenever a call is made to that DNS name in the firewall? So the firewall would resolve the name on the fly whenever someone/something tries to access that DNS name?
Or is it when you execute the fw script to load the rules into iptables? So in this case, it would resolve the DNS name that one time and then hard-code the resulting ip address into the iptable rules?

From what I read, I think its #1, but it's just not 100% clear to me. We have two servers for a certain function on our network. One is the primary server and one is backup.

alpha0.domain.com
alpha1.domain.com

In DNS we have this:

alpha.domain.com -> alpha0.domain.com

If the primary server goes down and we need to switch to the backup, I just change our local DNS record to point to alpha1.domain.com instead.

So back to the firewall, if I just put in a Domain Object as alpha.domain.com, do I have to reload the firewall rules every time we switch to the backup alpha server and change the DNS record? Or will the firewall automatically resolve to the correct address even after the switch?

© Server Fault or respective owner

Related posts about fwbuilder

fwbuilder/iptables manually scripted + autogenerated rules at startup?

as seen on Server Fault - Search for 'Server Fault'
Fedora 11 Our previous IT-guy setup iptable rules on our firewall in a way that is confusing me and he didn't document any of it. I was hoping someone could help me make some sense of it. The iptables service is obviously starting at startup, but the /etc/sysconfig/iptables file was untouched (default… >>> More
FWBuilder DNS Object Run Time - when exactly does it resolve the DNS name?

as seen on Server Fault - Search for 'Server Fault'
In Firewall Builder, when you use the DNS Object and set it to run time, when exactly does the firewall (iptables in our case) actually resolve the DNS name? Is it whenever a call is made to that DNS name in the firewall? So the firewall would resolve the name on the fly whenever someone/something… >>> More
Firewalls: What is the difference between Policy, NAT and Routes?

as seen on Server Fault - Search for 'Server Fault'
I'm learning fwbuilder and firewalls in general. I don't understand the differences between Policy, NAT and Routes. They all seem like they are just ways to tell the data where to go depending on what it is and where its coming from. What is the real difference? Is a properly configured firewall… >>> More

Related posts about iptables

Sometimes this script fails to update the iptables

as seen on Server Fault - Search for 'Server Fault'
It does not happen often, but sometimes after running the below script, checking the iptables with service iptables status shows that they weren't updated and the script doesn't output any error. The iptables is structured as look-up tree (long repeated sections snipped): #!/bin/sh iptables -t… >>> More
My current iptable configuration doesn't work [on hold]

as seen on Server Fault - Search for 'Server Fault'
sudo chkconfig iptables off /etc/init.d/iptables on ### Clear/flush iptables sudo iptables -F sudo iptables -P INPUT ACCEPT sudo iptables -P OUTPUT ACCEPT sudo iptables -P FORWARD ACCEPT ### Allow SSH iptables -A INPUT -i eth0 -p tcp --dport 22 -m state --state NEW,ESTABLISHED -j ACCEPT iptables… >>> More
L2TP iptables port forward

as seen on Server Fault - Search for 'Server Fault'
Hi all, I'm setting up port forwarding for an L2TP VPN connection to the local Windows 2003 VPN server. The router is a simpel Debian machine with iptables. The VPN server works perfect. But I cannot log in from the WAN. I'm missing something. The VPN server is using a pre-shared key (L2TP) and… >>> More
iptables -P FORWARD DROP makes port forwarding slow

as seen on Server Fault - Search for 'Server Fault'
I have three computers, linked like this: box1 (ubuntu) box2 router & gateway (debian) box3 (opensuse) [10.0.1.1] ---- [10.0.1.18,10.0.2.18,10.0.3.18] ---- [10.0.3.15] | box4, www [10.0.2.1] Among other… >>> More
IPtables AWS EC2 NAT/Reverse NAT - For Reverse Proxy style setup but with IPtables

as seen on Server Fault - Search for 'Server Fault'
I was thinking initially needing to do a reverse proxy or something so I could get some SSL/TLS traffic look like it is being terminated at a server and IP address in the AWS cloud, and then that traffic is forwarded onto our actual web servers that aren't in the cloud... I've not done much iptables… >>> More