Bridged APN

Harald Welte laforge at
Tue Apr 7 18:51:53 UTC 2020

Hi David,

On Tue, Apr 07, 2020 at 06:18:23PM +0200, Harald Welte wrote:
> On Mon, Apr 06, 2020 at 04:29:21PM -0400, david at wrote:
> > Does anyone have any experience with a bridged APN on Open5GS?
> As far as I know, 3GPP didn't really introduce "Ethernet" type PDN contexts
> until very recent releases.  For a long time, IPv4, IPv6 and IPv4v6 were the
> only available options.

I just checked: Etehernet type PDN connections are only supported in 5G,
but not in 4G/EPC.  Even Releae 15 doesn't mention it at all.

So whatever some vendors may be offering, I would bet it is not really any
actual Ethernet bridging.  It may be more something like proxy-ARP on the PGW
side, but still only passing IP over the 4G network.

The big question is: What is it used for, and what are the requirements of that
use case?  A real Ethernet bridge would be transparent regarding the MAC addresses
on both sides.  And that's what I'm stating is not possible over 4G as per 3GPP specs.

- Harald Welte <laforge at>  
"Privacy in residential applications is a desirable marketing option."
                                                  (ETSI EN 300 175-7 Ch. A6)

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