characteristics of interface type dummy

I’ve configured an interface ‘nonlocal’ with type dummy

ip link add nonlocal type dummy

on that interface are some IPv6 addresses configured. Now an apache can start with some ip based vhosts on above-said ipv6 addresses.

The “real” addresses get configured on the phyiscal interface if a second machine crashes (failover). Everything works a expected.

But I would like to know the exact characteristics of such a dummy interface (on RHEL6 & 7). Is there a homepage or something similar which explains that type?

Asked By: Benedikt Bock

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According to this and according to the source code, dummy interfaces appear to be kind of like the /dev/null of network interfaces. The interface will never receive a packet, and any packet you send to it goes nowhere. Here‘s dummy transmit definition for kernel v6.6 which frees the buffer without doing much.

For your use case, you probably don’t need a dummy interface at all. You can probably achieve what you need to binding the virtual IP address in question as a secondary IP address on the loopback interface (lo) as either a /32 (for IPv4) or /128 (for IPv6).

Answered By: Celada
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