Bind Multiple IP Addresses to a Single Network Interface Card (NIC)

http://www.xenocafe.com/tutorials/linux/redhat/bind_multiple_ip_addresses_to_single_nic/index.php

Assign Virtual IPs to your NIC

Can a network card have multiple IPs assigned to it?
The answer is absolutely yes! Some times, for example when you run several servers on a machine or when you need IP-based Apache virtualhosts, it is useful to bind a server or a virtualhost on its own IP address. I am not going to get into much detail on the pros and cons of virtual IPs, it would be pointless anyway since I am no pro, but here is how it is done.

Assigning a virtual IP to a NIC is a very easy task either you use the system-config-network tool or just do some text file editing. The script ifconfig can also be used to create a virtual network interface, but this would not be permanent since the changes ifconfig makes do not survive a reboot. In this post I’ll stick with the “manual” way…

In Fedora, all information about the network interfaces is kept in the following directories:

• /etc/sysconfig/network-scripts/
• /etc/sysconfig/networking/

I assume that the default NIC configuration script is:
/etc/sysconfig/network-scripts/ifcfg-eth0. Mine looks like this:

DEVICE=eth0
BOOTPROTO=static
BROADCAST=192.168.0.255
HWADDR=00:00:00:00:00:00
IPADDR=192.168.0.1
NETMASK=255.255.255.0
NETWORK=192.168.0.0
ONBOOT=yes
TYPE=Ethernet
GATEWAY=192.168.0.254

BOOTPROTO: sets the protocol that is used when the device is initialized. Since we use static IPs we set it to static.
HWADDR: is the MAC address of your network card. Do not change it. If this is missing in your configuration file, then don’t add it.
The rest of the options used are self-explanatory.

Make a copy of this in the same directory naming the new file ifcfg-eth0:1

# cp ifcfg-eth0 ifcfg-eth0\:1

eth0:1 is an alias of the eth0 interface. Now, let’s assign a different IP address to eth0:1. Other NIC aliases could be named eth0:2, eth0:3 etc. Fire up your favourite text editor and edit ifcfg-eth0:1. The modifications are shown in bold:

DEVICE=eth0:1
BOOTPROTO=static
BROADCAST=192.168.0.255
HWADDR=00:00:00:00:00:00
IPADDR=192.168.0.101
NETMASK=255.255.255.0
NETWORK=192.168.0.0
ONBOOT=yes
TYPE=Ethernet
GATEWAY=192.168.0.254

So, its IP address will be 192.168.0.101. Save the file and copy it to /etc/sysconfig/networking/devices/:

# cp ifcfg-eth0\:1 /etc/sysconfig/networking/devices/

Also, copy it to your default network profile or whichever profile you use:

# cp ifcfg-eth0\:1 /etc/sysconfig/networking/profiles/default/

Now, bring up the new interface using the ifup script:

# ifup eth0\:1

Running ifconfig, the new interface should be listed. You can also check it by pinging:

# ping 192.168.0.101

You can now assign a host name on this virtual interface, by updating your local DNS server’s zone files or by adding it to the /etc/hosts files on all your LAN computers.

That’s it.

From http://www.g-loaded.eu/2005/11/05/assign-virtual-ips-to-your-nic/

One network card with 2 IP adresses

Every ethernet interface can have any number of aliases in the form

ethX:Y

For example, since you have one ethernet card, it's probably "eth0". You
can have as many IP's as you want that attach to the "virtual ethernet
cards" eth0:0, eth0:1, eth0:2, eth0:3 . . . you get the idea. To assign an
IP to one of these cards, just type (as root)

ifconfig eth0:1 10.1.1.2 (or some such address.)
That's all there is to it! If you want to make these settings permanent
over boot, add the 'ifconfig' line to /etc/rc.d/rc.local or put it into
the redhat network startup scripts.

Port mappings

This is a simple list of what applications use which TCP ports.

TCP Port	Application
7	Echo – for Ping.
20	FTP data port – for active FTP connections.
21	FTP command
23	Telnet
25	SMTP
42	WINS
53	DNS
79	Finger
80	HTTP (web server)
110	POP3
119	NNTP
135	(Microsoft Windows) DCOM Service Control Manager / Remote Procedure Call service.
161	SNMP
162	SNMP Trap
443	SSL HTTP. Default port for Secure Socket Layer communications for Web servers (Secure HTTP).
444	Sharepoint uses for SSL HTTP.
465	SSL SMTP
993	SSL IMAP
995	SSL POP
1433	Microsoft SQL-Server.
1521	Port on which the Oracle RDBMS Listener service listens for new connections.
1723	PPTP VPN (used together with protocol 47, GRE)
2082	cPanel
2083	SSL cPanel
2095	Webmail
2096	SSL Webmail
3306	MySQL.
3389	Microsoft Terminal Server, Remote Desktop client. Windows Remote Assistance.
4125	Remote Web Workplace (RWW).
4899	Microsoft Remote Administrator.
5800	VNC web-browser server listens on port 5800 + display number.
5900	Default port for VNC (display 0). VNC server listens on port 5900 + display number. The VNC viewer connects on the port.
5901	Port used for VNC display 1.
5902	Port used for VNC display 2.
8080	Popular alternative port for HTTP, which is normally served on port 80.

From http://www.cryer.co.uk/brian/misc/port_mappings.htm