Difference between loopback and dummy interfaces for use in Linux routing

[Alexander Zubkov]

Hi,

One of the differences is when you configure some prefix on lo you get
route like this:
local 127.0.0.0/8 dev lo ...
And with dummy it is not the case.
This route type makes kernel consider every address from this space as
local - bind on it, reply to pings etc.

On Fri, Apr 27, 2018 at 11:40 AM, Anton Danilov <
littlesmilingcloud at gmail.com> wrote:

> Hi.
> There isn't a difference from perspective of routing.
>
> On 27 April 2018 at 11:52, Wilhelm Schuster <ws at rot13.io> wrote:
> > Hi,
> >
> > I’m learning about IP-networking and am in the process of setting up a
> Linux router using bird. During my research I’ve come across the usage of
> loopback interfaces. I could gather that this is done, because Ethernet
> interfaces for example (in contrast to loopbacks) can go down making the
> addresses configured on them unavailable. In addition, the kernel accepts
> packets destined to loopbacks addresses on other interfaces making these
> addresses available on multiple interfaces and not just the loopback.
> >
> > On Linux I found both the lo(opback), and dummy interfaces recommended
> to achieve the behavior outlined above. What I’m struggling with is
> understanding the differences between both interface types (besides the
> obvious difference in packet processing) and when to use which. Searching
> this mailing list I’ve seen people use lo, on other sites dummy interfaces
> are recommended. From a quick test (assigning address to lo/dummy;
> pinging/receiving pings on the host) I wasn’t able to find a difference.
> >
> > When should I use which interface?
> >
> > Cheers, Wilhelm.
>
>
>
> --
> Anton.
>
>
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