[Bridge] kernel doesn't support bridge with a ppp interface ?

Dylan Hall dylan at citylink.co.nz
Thu Jun 19 15:28:23 PDT 2008

It's a little unclear what your setup is, but let me take a guess and
make some suggestions :)

1)  Assuming a setup something like the following


In the above, I would assume the goal is to join (bridge) LAN A and LAN
B together?

You could configure basic IP across the PPP link so that the two linux
boxes can reach each other. 

You then configure something like vtun or etherip to run over the IP/PPP
link between the two linux boxes.

Finally you setup bridges at each end, the result would look something

LAN A --- (ETH){BR on LINUX A}(TUN) --- (PPP) --- (TUN){BR on LINUX
B}(ETH) --- LAN B

The etherip has the caveat that it doesn't support fragmentation so will
only work if the PPP link supports a large MTU, say 1540 or greater.

2) A less likely scenario is

PPP Client --- (ETH)[LINUX](ETH) --- PPP Server

In the above you want to get your PPP session going through a linux box
in the middle.

If the PPP is PPPoE, adding the ETH's to a bridge on the linux box
should be sufficient. 

If it's some other variant of PPP you might be able to use L2TP to
tunnel the PPP between end points. I've seen this done in a DSL/BRAS
environment where the BRAS wasn't directly attached to the DSLAMs. I
suspect this is far from straight forward.


On Thu, 2008-06-19 at 23:49 +0800, c.j wrote:

> >We use vtun which is a userland option, a little slow but offers
> rate-limiting and some other nice to have features.
> >When we require the lowest possible overhead option, we use the
> etherip kernel patches.
> Thanks for your kind suggestion.  Whether the etherip patches can
> transmit ppp packet? Since I'm not  familiar  with them , I need some
> time to read them if so.
> Regards~
> --
> c.j
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