SRP527W MTU on PPPoE

[MIKE JENKINS]

Using BT FTTC in the UK, the supplied VDSL modem supports baby jumbo frames, so we should be able to use 1500 bytes of MTU on the Ethernet WAN port of a SRP527W.

From older firmware manuals, it appears that there used to be an option in the WAN setup to allow MTU greater than 1492, but it's not there in firmware

1.01.27 (007). There's a box to change the MTU, but it will not accept values greater than 1492.

Has the setting moved or is it no longer possible?

[MIKE JENKINS]

An update...

You can manipulate the page in Chrome/Firefox etc to remove the validation of the box and it allows you to increase the MTU to 1500. We're just testing to see if it actually uses the value.

Incidentally, this is a good way to circumvent quite a bit of the SRP's security. (eg disallow remote upgrades etc).

[MIKE JENKINS]

Unfortunately the LNS still reports the MTU as 1492, so it doesnt work.

Maybe the switch in the srp supports jumbo frames, but the router part doesn't.