PPPoE WAN working on router but not LAN clients

General questions
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22

Thanks @marc_s, virtualisation is a good point, the proxmox host MTU is default (=1500), so that likely explains my max 1492 PPPoE MTU.

However, is there anything more to gain than 8 bytes/0.5% per packet? E.g. non-TCP/UDP traffic (Wireguard comes to mind, which seems to be working on with 1492 MTU)?

If I want to get 1500 MTU in PPPoE I need to edit the proxmox host interfaces + the underlying VLAN interface + the adopted VM MTU, the chance I’ll forget one of those is significant.

23

I don’t think you’ll see a huge performance increase or anything, no.
I just did it because I could, not because I needed to.

24

The advantage of having pppoe mtu at 1500, is preventing running into mtu problems…like you did.
Only TCP is fixable with mss-clamp, all other protocols rely on Path MTU Discovery, which requires proper ICMP allow rules along the entire path between client and server