Assigning IPs to one NIC
 

How many IPs can I configure on Linux system on one NIC ??

If its different for freeBSD, Fedora and RedHat Linux then whats the exact figures for each ....

Re: Assigning IPs to one NIC
 

That's actually a tough question to answer. I can tell you, though, that Fedora and RedHat will likely be the same. You will probably have to manually configure them via the ifconfig command, rather than using the GUI tools, as they usually only support one address per interface.

I tried going through the source code for both FreeBSD and Linux, but really didn't find a way to go. Perhaps this would be a great question to pose to each the Linux and FreeBSD kernel developers' Network mailing lists?

Re: Assigning IPs to one NIC
 

You'd want to use the 'alias' command with ifconfig, as described in the FreeBSD Handbook. You set this in /etc/rc.conf

Example:

alias_fxp0="inet 10.0.3.4 netmask 255.255.255.0"

Re: Assigning IPs to one NIC
 

Here's how we do it where I work. Just set up an alias for the ethernet port you want to apply multiple IP addresses to. Theoretically you could apply as many IP addresses to an ethernet port as you want. We typically have never used more than 4. We're also using RedHat Enterprise Linux Server v3/v4.

[ifcfg-eth1]
DEVICE=eth1
BOOTPROTO=none
HWADDR=00:D0:B7:4D:50:ED
ONBOOT=yes
USERCTL=no
PEERDNS=yes
TYPE=Ethernet
IPADDR=192.168.0.102
NETMASK=255.255.255.0
NETWORK=192.168.0.0
BROADCAST=192.168.0.255
GATEWAY=192.168.0.1

[ifcfg-eth1:1]
DEVICE=eth1:1
BOOTPROTO=none
ONBOOT=yes
IPADDR=192.168.0.121
NETMASK=255.255.255.0
USERCTL=no
IPV6INIT=no
PEERDNS=yes
GATEWAY=192.168.0.1
TYPE=Ethernet

These files are located in /etc/sysconfig/network-scripts. Configuring these through the GUI utilities will work almost as well as manually editing the files yourself.

Hope this helps.

Re: Assigning IPs to one NIC
 

And thats why I was asking ... how many aliases like these can I make in Linux?

Re: Assigning IPs to one NIC
 

Ok... here's what I have on the maximum number of IP aliases. According to my documentation, as of Linux kernel 2.0.3 and up the default maximum number of aliases is 256. This can be changed by updating or creating this file and putting the new maximum number...

/proc/sys/net/core/net_aliax_max

Does that answer your question?

Re: Assigning IPs to one NIC
 

One of the things not pointed out here was the ability of the alias
to exist on more than one subnet. Meaning eth0 is the first and eth:1
the second in traditionial fashion. This comes in really handy when merging
domains or for load balancing applications such as Oracle.

In the most basic sence, you can really name it anything as long as
the mac addresses are bound to the correct common device. You can
even go as far as to edit the scripts and files by hand in
/etc/sysconfig/network*.

just copy the initial eth0 files to the new name and edit appropriately.

after:

ifup eth0:1

or the like or simply:
service network restart

you can also use miitool or the current version, ethtool
to set persistant forced speeds, duplexing and whatnot.

gotta love it!