Detailed analysis of RHEL 5 firewall settings

As we all know, firewalls are an important guarantee for computer security, so they are also very important in the RHEL 5 firewall settings, this is precisely because it is very important, so we need to provide a detailed description of this important and tedious RHEL 5 firewall settings.

After Oracle is installed on RHEL5.2, you can start Oracle exercises. Because my RHEL is installed on a virtual machine, it is not so convenient to operate on the Virtual Machine and the response speed is slow. Fortunately, Oracle 10 Gb has a B/S management interface, so it is not easy and quick to operate on the VM Host! Virtual Machine (VM) IP: 10.10.10.197, virtual machine host ip: 10.10.10.198, bridging mode Bridged) connection. However, when I enter the address http: // 10.10.10.197: 1158/em in the address bar of my browser, the message "Firefox cannot establish a connection to the 10.10.10.197: 1158 server" is displayed ". It can be executed very effectively in the VM, And it is okay to Ping 10.10.10.197 on 10.10.10.198. Start to find a solution. Go to System-> Administration-> Security Level and Firewall. The RHEL 5 firewall is Enabled. Trusted Services clearly have the WWW (HTTP) service. Why not?

Security and firewall menu)

Firewall Status and settings)

View the service from System> Administration> Server Settings> Services and find a service named iptables. It turns out to be a Firewall Service.

Firewall Service)

There is a Stop. Like Services in Windows, Stop it. Refresh http: // 10.10.10.197: 1158/em on 10.10.10.198. Everything is under expectation. The page is displayed! It seems that the firewall configuration is still a problem. Search on the network, you can perform the following configuration reference: http://linux.ccidnet.com/art/9513/20070601/1098119_1.html ):

1. view existing configurations of RHEL 5 firewall
[Root @ RHEL ~] # Iptables-L-n
Chain INPUT (policy ACCEPT)
Target prot opt source destination
RH-Firewall-1-INPUT all -- 0.0.0.0/00.0.0.0/0
ACCEPT tcp -- 0.0.0.0/00.0.0.0/0 tcp dpt: 1158
Chain FORWARD (policy ACCEPT)
Target prot opt source destination
RH-Firewall-1-INPUT all -- 0.0.0.0/00.0.0.0/0
Chain OUTPUT (policy ACCEPT)
Target prot opt source destination
Chain RH-Firewall-1-INPUT (2 references)
Target prot opt source destination
ACCEPT all -- 0.0.0.0/00.0.0.0/0
ACCEPT icmp -- 0.0.0.0/00.0.0.0/0 icmp type 255
ACCEPT esp -- 0.0.0.0/00.0.0.0/0
ACCEPT ah -- 0.0.0.0/00.0.0.0/0
ACCEPT udp -- 0.0.0.0/0224.0.0.20.udp dpt: 5353
ACCEPT udp -- 0.0.0.0/00.0.0.0/0 udp dpt: 631
ACCEPT tcp -- 0.0.0.0/00.0.0.0/0 tcp dpt: 631
ACCEPT all -- 0.0.0.0/00.0.0.0/0 state RELATED, ESTABLISHED
ACCEPT tcp -- 0.0.0.0/00.0.0.0/0 state NEW tcp dpt: 21
ACCEPT tcp -- 0.0.0.0/00.0.0.0/0 state NEW tcp dpt: 22
ACCEPT tcp -- 0.0.0.0/00.0.0.0/0 state NEW tcp dpt: 443
ACCEPT tcp -- 0.0.0.0/00.0.0.0/0 state NEW tcp dpt: 23
ACCEPT tcp -- 0.0.0.0/00.0.0.0/0 state NEW tcp dpt: 80
REJECT all -- 0.0.0.0/00.0.0.0/0 reject-with icmp-host-prohibited

2. Clear RHEL 5 firewall configuration
[Root @ RHEL ~] # Iptables-F
[Root @ RHEL ~] # Iptables-X
[Root @ RHEL ~] #/Etc/rc. d/init. d/iptables save
Saving firewall rules to/etc/sysconfig/iptables: [OK]
[Root @ RHEL ~] # Iptables-L-n
Chain INPUT (policy ACCEPT)
Target prot opt source destination
Chain FORWARD (policy ACCEPT)
Target prot opt source destination
Chain OUTPUT (policy ACCEPT)
Target prot opt source destination

3. Add RHEL 5 firewall configuration
Add specific ports to the allowed list. For example, EM uses 1158, telnet uses 23, and Litener uses 1521.
[Root @ RHEL ~] # Iptables-a input-p tcp -- dport 1158-j ACCEPT
[Root @ RHEL ~] # Iptables-a input-p tcp -- dport 23-j ACCEPT
[Root @ RHEL ~] # Iptables-a input-p tcp -- dport 1521-j ACCEPT

Save Configuration:
[Root @ RHEL ~] #/Etc/rc. d/init. d/iptables save
Saving firewall rules to/etc/sysconfig/iptables: [OK]

Check the current configuration:
[Root @ RHEL ~] # Iptables-L-n
Chain INPUT (policy ACCEPT)
Target prot opt source destination
ACCEPT tcp -- 0.0.0.0/00.0.0.0/0 tcp dpt: 1158
ACCEPT tcp -- 0.0.0.0/00.0.0.0/0 tcp dpt: 23
ACCEPT tcp -- 0.0.0.0/00.0.0.0/0 tcp dpt: 1521
Chain FORWARD (policy ACCEPT)
Target prot opt source destination
Chain OUTPUT (policy ACCEPT)
Target prot opt source destination

Restart the Firewall Service:
[Root @ RHEL ~] # Service iptables restart
Flushing firewall rules: [OK]
Setting chains to policy ACCEPT: nat filter [OK]
Unloading iptables modules: [OK]
Applying iptables firewall rules: [OK]
Loading additional iptables modules: ip_conntrack_netbios_n [OK] ntrack_ftp
After this configuration, the access to EM on 10.10.10.198 is normal, and PL/SQL Developer can also be connected normally.

In fact, if you follow the steps carefully, it is easier to master the RHEL 5 firewall settings. The above is my summary of the RHEL 5 firewall settings, we hope this will help you use the RHEL 5 firewall.

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