IP MTU on gif and gre interfaces (with and without IPSec encryption)

Mon Mar 23 09:08:56 UTC 2020

Hi all,

> Am 23.03.2020 um 06:00 schrieb Victor Sudakov <vas at sibptus.ru>:
> I've noticed that a newly created gre0 interface has the expected "mtu 1476"
> value, but a newly created gif0 interface has "mtu 1280", why would the
> default be so low?

gif is frequently used as the innermost encapsulation like in gif tunnel
across host mode IPsec. Then there might be PPPoE, too. Possibly a
VLAN tag ...
So most probably the idea is to go as low as possible for arbitrary additional
encapsulations while still satisfying the minimum requirement for IPv6.

For the others: no idea, I guess historical ;-)

Patrick
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