IP-Alias.pdf

Setting up IP Aliasing on A Linux Machine

Mini−HOWTO

Harish Pillay

h.pillay@ieee.org

Joy Yokley − Converted document from HTML to DocBook v4.1 (SGML)

2001−01−23

Revision History

Revision 1.2

2001−01−26

Revised by: JEY

Revision 1.1

2001−01−24

Revised by: JEY

Revision 1.0

1997−01−13

Revised by: HP

This is a cookbook recipe on how to set up and run IP aliasing on a Linux box and how to set up the machine

to receive e−mail on the aliased IP addresses.

Setting up IP Aliasing on A Linux Machine Mini−HOWTO

Table of Contents

1. My Setup. .........................................................................................................................................................1

2. Commands. ......................................................................................................................................................2

3. Troubleshooting: Questions and Answers. ...................................................................................................4

3.1. Question: How can I keep the settings through a reboot?. ...............................................................4

3.2. Question: How do I set up the IP aliased machine to receive e−mail on the various aliased IP addresses (on a machine using sendmail)?

4. Acknowledgements .........................................................................................................................................6

1. My Setup

IP Alias is standard in kernels 2.0.x and 2.2.x, and available as a compile−time option in 2.4.x (IP

Alias has been deprecated in 2.4.x and replaced by a more powerful firewalling mechanism.)

IP Alias compiled as a loadable module. You would have indicated in the "make config" command to

make your kernel, that you want the IP Masq to be compiled as a (M)odule. Check the Modules

HOW−TO (if that exists) or check the info in

/usr/src/linux/Documentation/modules.txt.

· I have to support 2 additional IPs over and above the IP already allocated to me.

A D−Link DE620 pocket adapter (not important, works with any Linux supported network adapter).

1. My Setup

2. Commands

1. Load the IP Alias module (you can skip this step if you compiled the module into the kernel):

/sbin/insmod /lib/modules/`uname −r`/ipv4/ip_alias.o

2. Setup the loopback, eth0, and all the IP addresses beginning with the main IP address for the eth0

interface:

/sbin/ifconfig lo 127.0.0.1

/sbin/ifconfig eth0 up

/sbin/ifconfig eth0 172.16.3.1

/sbin/ifconfig eth0:0 172.16.3.10

/sbin/ifconfig eth0:1 172.16.3.100

172.16.3.1 is the main IP address, while .10 and .100 are the aliases. The magic is the eth0:x where

x=0,1,2,...n for the different IP addresses. The main IP address does not need to be aliased.

3. Setup the routes. First route the loopback, then the net, and finally, the various IP addresses starting

with the default (originally allocated) one:

/sbin/route add −net 127.0.0.0

/sbin/route add −net 172.16.3.0 dev eth0

/sbin/route add −host 172.16.3.1 dev eth0

/sbin/route add −host 172.16.3.10 dev eth0:0

/sbin/route add −host 172.16.3.100 dev eth0:1

/sbin/route add default gw 172.16.3.200

That's it.

In the example IP address above, I am using the Private IP addresses (RFC 1918) for illustrative purposes.

Substitute them with your own official or private IP addresses.

The example shows only 3 IP addresses. The max is defined to be 256 in

/usr/include/linux/net_alias.h. 256 IP addresses on ONE card is a lot :−)!

Here's what my /sbin/ifconfig looks like:

lo Link encap:Local Loopback

inet addr:127.0.0.1 Bcast:127.255.255.255 Mask:255.0.0.0

UP BROADCAST LOOPBACK RUNNING MTU:3584 Metric:1

RX packets:5088 errors:0 dropped:0 overruns:0

TX packets:5088 errors:0 dropped:0 overruns:0

eth0 Link encap:10Mbps Ethernet HWaddr 00:8E:B8:83:19:20

inet addr:172.16.3.1 Bcast:172.16.3.255 Mask:255.255.255.0

UP BROADCAST RUNNING PROMISC MULTICAST MTU:1500 Metric:1

RX packets:334036 errors:0 dropped:0 overruns:0

TX packets:11605 errors:0 dropped:0 overruns:0

Interrupt:7 Base address:0x378

eth0:0 Link encap:10Mbps Ethernet HWaddr 00:8E:B8:83:19:20

inet addr:172.16.3.10 Bcast:172.16.3.255 Mask:255.255.255.0

UP BROADCAST RUNNING MTU:1500 Metric:1

RX packets:0 errors:0 dropped:0 overruns:0

TX packets:0 errors:0 dropped:0 overruns:0

eth0:1 Link encap:10Mbps Ethernet HWaddr 00:8E:B8:83:19:20

inet addr:172.16.3.100 Bcast:172.16.3.255 Mask:255.255.255.0

UP BROADCAST RUNNING MTU:1500 Metric:1

2. Commands

Setting up IP Aliasing on A Linux Machine Mini−HOWTO

RX packets:1 errors:0 dropped:0 overruns:0

TX packets:0 errors:0 dropped:0 overruns:0

And /proc/net/aliases :

device family address

eth0:0 2 172.16.3.10

eth0:1 2 172.16.3.100

And /proc/net/alias_types :

type name n_attach

2 ip 2

Of course, the stuff in /proc/net was created by the ifconfig command and not by hand!

2. Commands

Plik z chomika:

Inne pliki z tego folderu:

Inne foldery tego chomika: