Bug with 1508 MTU when using PPPoE

Installing and Using OpenWrt
1

I am using a BT (UK) connection, via FTTC and it uses PPPoE.

I am using a TP-LINK Archer C7 and a Huawei HG612 (the latter compatible with a 1508 MTU when used in bridge mode).

BT allows the use of a 1508 MTU but there is a bug within OpenWrt that prevents this from working properly. If you set 1508 in the web interface of OpenWrt, the MTU is not applied, it sticks at 1492.

I followed instructions found here: https://www.middling.uk/blog/2015/03/customising-openwrt-to-my-needs/.

Adding

config interface 'eth0'
	option ifname 'eth0'
	option mtu '1508'

to /etc/config/network and ensuring the 1508 MTU is (still) set for PPPoE, resolves the problem and I can use the 1500 MTU as expected.

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