TL-WR1043ND v4 eth0 MTU max 1516 (OpenWrt 18.06.4)

Installing and Using OpenWrt
1

I'm trying to set MTU on eth0 device to more than 1500, I'd really like to go to 1532 in order to stop batman-adv complaining about fragmentation.

However, there seems to be a hard limit of 1516:

ifconfig eth0 mtu 1516
ifconfig: SIOCSIFMTU: Resource busy

ifconfig eth0 mtu 1517
ifconfig: SIOCSIFMTU: Invalid argument

Is this a hardware limit?

2

Unless you're using jumbo frames, the limit should be 1500, not 1516.

1 Like
3

Are you sure you need this on eth0?
Here you can see how it works on wi-fi interface (with BATMAN): How to Set MTU on "Bare" Wireless Interface Using config/UCI?

4

Not to mention “can use” - not all devices support jumbo frames, especially consumer-grade gear.

2 Likes
5

I'm using batman-adv between two routers with multi-link, the first is a wireless mesh, on which I could increase the MTU. The second is a gigabit ethernet connection, which I added to increase bandwidth between them. This way, batman-adv is able to recover from connectivity loss and choose the best path.