On Thu, 6 Dec 2001, Richard Rauch wrote:

> > > > mouse-pppoe sets it to 1400???  I don't know why its so low, pppoe adds 8
> > > > bytes of encapsulation, so thats an mtu of 1492 over ethernet (mtu 1500).
> > >
> > > prometheus# ifconfig ppp0
> > > ppp0: flags=8051<UP,POINTOPOINT,RUNNING,MULTICAST> mtu 1400
> > >         inet 65.68.73.156 -> 65.68.75.254 netmask 0xff000000
> > >         inet6 fe80::240:f4ff:fe2f:4de8%ppp0 -> :: prefixlen 64 scopeid 0x4
> >
> > Strange, I don't know why mouse-ppoe uses such a low mtu - its a waste
>
> I thought that PPP negotiated this kind of thing automatically---so the
> 1400 limit is presumably imposed by the other side of the line, yes?

Um, my understanding is that each end of a PPP link has an MTU and MRU
(max receive unit), and the maximum packet in each direction is the
minimum of the MTU on the sender and MRU on the receiver.  In that case,
either end could affect the setting.  I could be wrong though.

Rick