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binding and bonding

(Written by Paul Cobbaut, https://github.com/paulcobbaut/, with contributions by: Alex M. Schapelle, https://github.com/zero-pytagoras/)

Sometimes a server needs more than one ip address on the same network card, we call this binding ip addresses.

Linux can also activate multiple network cards behind the same ip address, this is called bonding.

This chapter will teach you how to configure binding and bonding on the most common Linux distributions.

binding on Redhat/Fedora

binding extra ip addresses

To bind more than one ip address to the same interface, use ifcfg-eth0:0, where the last zero can be anything else. Only two directives are required in the files.

[root@linux ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0:0
DEVICE="eth0:0"
IPADDR="192.168.1.133"
[root@linux ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0:1
DEVICE="eth0:0"
IPADDR="192.168.1.142"

enabling extra ip-addresses

To activate a virtual network interface, use ifup, to deactivate it, use ifdown.

[root@linux ~]# ifup eth0:0
[root@linux ~]# ifconfig | grep 'inet '
          inet addr:192.168.1.99  Bcast:192.168.1.255  Mask:255.255.255.0
          inet addr:192.168.1.133  Bcast:192.168.1.255  Mask:255.255.255.0
          inet addr:127.0.0.1  Mask:255.0.0.0
[root@linux ~]# ifup eth0:1
[root@linux ~]# ifconfig | grep 'inet '
          inet addr:192.168.1.99  Bcast:192.168.1.255  Mask:255.255.255.0
          inet addr:192.168.1.133  Bcast:192.168.1.255  Mask:255.255.255.0
          inet addr:192.168.1.142  Bcast:192.168.1.255  Mask:255.255.255.0
          inet addr:127.0.0.1  Mask:255.0.0.0

verifying extra ip-addresses

Use ping from another computer to check the activation, or use ifconfig like in this screenshot.

[root@linux ~]# ifconfig 
eth0   Link encap:Ethernet  HWaddr 08:00:27:DD:0D:5C  
       inet addr:192.168.1.99  Bcast:192.168.1.255  Mask:255.255.255.0
       inet6 addr: fe80::a00:27ff:fedd:d5c/64 Scope:Link
       UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
       RX packets:1259 errors:0 dropped:0 overruns:0 frame:0
       TX packets:545 errors:0 dropped:0 overruns:0 carrier:0
       collisions:0 txqueuelen:1000 
       RX bytes:115260 (112.5 KiB)  TX bytes:84293 (82.3 KiB)

eth0:0 Link encap:Ethernet  HWaddr 08:00:27:DD:0D:5C  
       inet addr:192.168.1.133  Bcast:192.168.1.255  Mask:255.255.255.0
       UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

eth0:1 Link encap:Ethernet  HWaddr 08:00:27:DD:0D:5C  
       inet addr:192.168.1.142  Bcast:192.168.1.255  Mask:255.255.255.0
       UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1

binding on Debian/Ubuntu

binding extra ip addresses

The configuration of multiple ip addresses on the same network card is done in /etc/network/interfaces by adding eth0:x devices. Adding the netmask is mandatory.

debian10:~# cat /etc/network/interfaces
# This file describes the network interfaces available on your system
# and how to activate them. For more information, see interfaces(5).

# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
iface eth0 inet static
address 192.168.1.34
network 192.168.1.0
netmask 255.255.255.0
gateway 192.168.1.1
auto eth0

auto eth0:0
iface eth0:0 inet static
address 192.168.1.233
netmask 255.255.255.0

auto eth0:1
iface eth0:1 inet static
address 192.168.1.242
netmask 255.255.255.0

enabling extra ip-addresses

Use ifup to enable the extra addresses.

debian10:~# ifup eth0:0
debian10:~# ifup eth0:1

verifying extra ip-addresses

Use ping from another computer to check the activation, or use ifconfig like in this screenshot.

debian10:~# ifconfig | grep 'inet '
      inet addr:192.168.1.34  Bcast:192.168.1.255  Mask:255.255.255.0
      inet addr:192.168.1.233  Bcast:192.168.1.255  Mask:255.255.255.0
      inet addr:192.168.1.242  Bcast:192.168.1.255  Mask:255.255.255.0
      inet addr:127.0.0.1  Mask:255.0.0.0

bonding on Redhat/Fedora

We start with ifconfig -a to get a list of all the network cards on our system.

[root@linux network-scripts]# ifconfig -a | grep Ethernet
eth0      Link encap:Ethernet  HWaddr 08:00:27:DD:0D:5C  
eth1      Link encap:Ethernet  HWaddr 08:00:27:DA:C1:49  
eth2      Link encap:Ethernet  HWaddr 08:00:27:40:03:3B

In this demo we decide to bond eth1 and eth2.

We will name our bond bond0 and add this entry to modprobe so the kernel can load the bonding module when we bring the interface up.

[root@linux network-scripts]# cat /etc/modprobe.d/bonding.conf 
alias bond0 bonding

Then we create /etc/sysconfig/network-scripts/ifcfg-bond0 to configure our bond0 interface.

[root@linux network-scripts]# pwd
/etc/sysconfig/network-scripts
[root@linux network-scripts]# cat ifcfg-bond0 
DEVICE=bond0
IPADDR=192.168.1.199
NETMASK=255.255.255.0
ONBOOT=yes
BOOTPROTO=none
USERCTL=no

Next we create two files, one for each network card that we will use as slave in bond0.

[root@linux network-scripts]# cat ifcfg-eth1
DEVICE=eth1
BOOTPROTO=none
ONBOOT=yes
MASTER=bond0
SLAVE=yes
USERCTL=no
[root@linux network-scripts]# cat ifcfg-eth2
DEVICE=eth2
BOOTPROTO=none
ONBOOT=yes
MASTER=bond0
SLAVE=yes
USERCTL=no

Finally we bring the interface up with ifup bond0.

[root@linux network-scripts]# ifup bond0
[root@linux network-scripts]# ifconfig bond0
bond0     Link encap:Ethernet  HWaddr 08:00:27:DA:C1:49  
          inet addr:192.168.1.199  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::a00:27ff:feda:c149/64 Scope:Link
          UP BROADCAST RUNNING MASTER MULTICAST  MTU:1500  Metric:1
          RX packets:251 errors:0 dropped:0 overruns:0 frame:0
          TX packets:21 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:39852 (38.9 KiB)  TX bytes:1070 (1.0 KiB)

The bond should also be visible in /proc/net/bonding.

[root@linux network-scripts]# cat /proc/net/bonding/bond0 
Ethernet Channel Bonding Driver: v3.5.0 (November 4, 2008)

Bonding Mode: load balancing (round-robin)
MII Status: up
MII Polling Interval (ms): 0
Up Delay (ms): 0
Down Delay (ms): 0

Slave Interface: eth1
MII Status: up
Link Failure Count: 0
Permanent HW addr: 08:00:27:da:c1:49

Slave Interface: eth2
MII Status: up
Link Failure Count: 0
Permanent HW addr: 08:00:27:40:03:3b

bonding on Debian/Ubuntu

We start with ifconfig -a to get a list of all the network cards on our system.

debian10:~# ifconfig -a | grep Ethernet
eth0      Link encap:Ethernet  HWaddr 08:00:27:bb:18:a4
eth1      Link encap:Ethernet  HWaddr 08:00:27:63:9a:95
eth2      Link encap:Ethernet  HWaddr 08:00:27:27:a4:92

In this demo we decide to bond eth1 and eth2.

We also need to install the ifenslave package.

debian10:~# aptitude search ifenslave
p ifenslave     - Attach and detach slave interfaces to a bonding device
p ifenslave-2.6 - Attach and detach slave interfaces to a bonding device
debian10:~# aptitude install ifenslave
Reading package lists... Done
...

Next we update the /etc/network/interfaces file with information about the bond0 interface.

debian10:~# tail -7 /etc/network/interfaces
iface bond0 inet static
 address 192.168.1.42
 netmask 255.255.255.0
 gateway 192.168.1.1
 slaves eth1 eth2
 bond-mode active-backup
 bond_primary eth1

On older version of Debian/Ubuntu you needed to modprobe bonding, but this is no longer required. Use ifup to bring the interface up, then test that it works.

debian10:~# ifup bond0
debian10:~# ifconfig bond0
bond0     Link encap:Ethernet  HWaddr 08:00:27:63:9a:95  
          inet addr:192.168.1.42  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::a00:27ff:fe63:9a95/64 Scope:Link
          UP BROADCAST RUNNING MASTER MULTICAST  MTU:1500  Metric:1
          RX packets:212 errors:0 dropped:0 overruns:0 frame:0
          TX packets:39 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0 
          RX bytes:31978 (31.2 KiB)  TX bytes:6709 (6.5 KiB)

The bond should also be visible in /proc/net/bonding.

debian10:~# cat /proc/net/bonding/bond0 
Ethernet Channel Bonding Driver: v3.2.5 (March 21, 2008)

Bonding Mode: fault-tolerance (active-backup)
Primary Slave: eth1
Currently Active Slave: eth1
MII Status: up
MII Polling Interval (ms): 0
Up Delay (ms): 0
Down Delay (ms): 0

Slave Interface: eth1
MII Status: up
Link Failure Count: 0
Permanent HW addr: 08:00:27:63:9a:95

Slave Interface: eth2
MII Status: up
Link Failure Count: 0
Permanent HW addr: 08:00:27:27:a4:92

practice: binding and bonding

  1. Add an extra ip address to one of your network cards. Test that it works (have your neighbour ssh to it)!

  2. Use ifdown to disable this extra ip address.

  3. Make sure your neighbour also succeeded in binding an extra ip address before you continue.

  4. Add an extra network card (or two) to your virtual machine and use the theory to bond two network cards.

solution: binding and bonding

  1. Add an extra ip address to one of your network cards. Test that it works (have your neighbour ssh to it)!

    Redhat/Fedora: add an /etc/sysconfig/network-scripts/ifcfg-ethX:X file as shown in the theory

    Debian/Ubuntu: expand the /etc/network/interfaces file as shown in the theory

  2. Use ifdown to disable this extra ip address.

    ifdown eth0:0

  3. Make sure your neighbour also succeeded in binding an extra ip address before you continue.

    ping $extra_ip_neighbour or ssh $extra_ip_neighbour

  4. Add an extra network card (or two) to your virtual machine and use the theory to bond two network cards.

    Redhat/Fedora: add ifcfg-ethX and ifcfg-bondX files in /etc/sysconfig/network-scripts as shown in the theory and don't forget the modprobe.conf

    Debian/Ubuntu: expand the /etc/network/interfaces file as shown in the theory and don't forget to install the ifenslave package