dhcpcd-discuss

Hi Scott

On 08/02/2019 11:04, Scott Leggett wrote:
> There's a bug report in Debian[0] that I can reproduce in dhcpcd 7.1.0.
> Essentially, setting a static interface_mtu doesn't seem to work as
> expected, though I am not sure if this configuration is even supported?
>
> Here's the interface configuration snippet - note the third line:
>
>      interface ens3
>      noipv6rs
>      static interface_mtu=1400
>      static ip_address=192.168.122.9/24
>      static routers=192.168.122.1
>      static domain_name_servers=192.168.122.1
>
> And here's the resulting interface - mtu 1500, when I would have
> expected 1400:
>
>      2: ens3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
>          link/ether 52:54:00:ba:4e:d6 brd ff:ff:ff:ff:ff:ff
>          inet 192.168.122.9/24 brd 192.168.122.255 scope global noprefixroute ens3
>             valid_lft forever preferred_lft forever
>          inet6 fe80::6486:7fbd:bf43:e57e/64 scope link
>             valid_lft forever preferred_lft forever
>
> Is there a bug here, is the configuration wrong, or is this simply not
> supported?

This is supported, but not quite how you expect.
MTU is now set per route rather than for the whole interface, so you can 
have a larger MTU for IPv6 than for IPv4.

Check output with `ip r`

Roy