[FS#3815] PPPoE interface naming creates issues for ping, traceroute, curl and scripts

OpenWrt Bugs openwrt-bugs at lists.openwrt.org
Wed May 19 08:31:44 PDT 2021


The following task has a new comment added:

FS#3815 - PPPoE interface naming creates issues for ping, traceroute, curl and scripts
User who did this - Jo-Philipp Wich (jow-)

> Why is that? Could you suggest some article explaining how it works? 

I can't refer to any article explaining this particular detail but it is an essential property of encapsulated protocols. PPPoE is PPP protocol frames encapsulated in ethernet frames. The ethX interface receives the raw, encapsulated traffic which is processed and unwrapped by the kernel and the resulting decapsulated traffic is sent to another network device, pppoe-wan in the case of OpenWrt or ppp0 on normal Desktop Linux distros.

This mechanism is the same for any kind of tunneling or encapsulation protocol like OpenVPN, gre, ipip tunnels, PPPoE and numerous others.

>  And if it's expected, why are mwan3 and ddns having trouble with it?

I don't know, maybe because the authors naively assumed that layer 2 netdev == layer 3 netdev in all cases, but as you noticed, that is not necessarily the case, e.g. for PPPoE links. Note that neither package is maintained in OpenWrt base, so there's nothing we can do about it here.

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