Prepare your server for additional IP addresses
If your server was not recently created, and does not use Gandi IA, you must update the appropriate Gandi support later. This software later is in charge of automatically configuring the server's interface during attachment.
Note that the installation is not mandatory if you are an expert and would like to configure the interface by yourself. We nevertheless recommend using the gandi-hosting-vm package in order to benefit from this feature. With Debian:
apt-get updateto update the list of packets
apt-get install gandi-hosting-vmto install the latest gandi-hosting-vm package
In expert mode, you must force the ARP responses to be sent from the most appropriate interface. For security reasons, we filter requests and ARP responses of each virtual server. This hinders you from transmitting the eth1 address/mac via eth0. You will also need to deactivate the reverse path RFC1812 origin validation, because your default route is on eth0, and the other interfaces will refuse any packet that does not come from their local network.
With Linux, you will obtain this configuration by modifying your configuration: in /etc/sysctl.conf :
net.ipv4.conf.all.arp_announce=2 net.ipv4.conf.all.arp_filter=0 net.ipv4.conf.all.rp_filter=0
then, by reloading the configuration file:
sysctl -f /etc/sysctl.conf
sysctl -w net.ipv4.conf.all.arp_announce=2 sysctl -w net.ipv4.conf.all.arp_filter=0 sysctl -w net.ipv4.conf.all.rp_filter=0
Define the sysctl settings that mention 'default' with the appropriate value in order to facilitate the dynamic attaching of interfaces. A specific configuration may therefore be applied to each interface.
Here is an example of the 'sysctl.conf' configuration file for three eth0, eth1, and eth2 interfaces, where eth1 is not used for outgoing traffic and filters incoming packets:
net.ipv4.conf.all.arp_filter = 0 net.ipv4.conf.default.arp_filter = 0
net.ipv4.conf.all.rp_filter = 0 net.ipv4.conf.default.rp_filter = 0 net.ipv4.conf.eth1.rp_filter = 1 ## Trafic local uniquement
net.ipv4.conf.eth1.arp_announce = 2 net.ipv4.conf.eth1.rp_filter = 0