How to DHCP request a second, different, IP for the same physical interface

dhclientdhcpgentooiproute2

(Similar to this question, but with two different DHCP-assigned IPs)

Is there any way to let dhclient or dhcpcd request two different IPs for one physical interface, e.g. via virtual interfaces eth0 and eth0:1? Maybe by letting eth0:1 have a different MAC? Or by creating a virtual eth1 bridged to eth0? Or can I use ip addr add directly somehow?

Best Answer

If eth0:1 has a different MAC, dhcpd should provide a second address automatically, unless it is on a different VLAN.

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Linux – Disable dhcp client over one interface

Something like:

auto lo eth0 eth1

iface lo inet loopback

iface eth1 inet static
        address 192.168.32.130
        netmask 255.255.255.0
        gateway 192.168.32.1

in your /etc/network/interfaces config file will assign your eth1 a static IP address.

How to configure radvd, dhcpd6, routing and /64 subnet based on delegated prefix by DHCPv6-PD server

I don't know the answer to your question, but I just want to warn you about using the DHCP server address as your default router. If that works it is by chance... In IPv6 the default route is communicated by RA's and not by DHCP.

You will need to enable forwarding, accepting RA's and sending out RS's. A problem here is that the kernel included in Centos6 does not allow you to do that. When forwarding is enabled then accepting RA's and sending RS's is disabled. There should be a CentosPlus kernel with the relevant patches though. See the mailing list thread / message at http://lists.centos.org/pipermail/centos/2011-April/thread.html#109756

The relevant sysctl.conf settings are:

net.ipv6.conf.all.forwarding=1
net.ipv6.conf.eth0.accept_ra=2
net.ipv6.conf.eth0.accept_ra_defrtr=1
net.ipv6.conf.eth0.router_solicitations=1

Best Answer

Related Solutions

Linux – Disable dhcp client over one interface

How to configure radvd, dhcpd6, routing and /64 subnet based on delegated prefix by DHCPv6-PD server

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