I've recently started using an RB2011 as my main router with all its PCQing and configurability and visibility
I've been trying to get a 1500 MTU working with RFC 4638. I've set the ether1 interface MTU to 1508 (as required) and set the MTU and MRU to 1500 on the PPPoE client connection. I did have it going through a bridge interface before, but this didn't seem to broach the 1492 MTU limit, (even after changing MTU in the bridge and the interface) so I removed that and put it directly on ether1. Since sorting that out, I seem to be connecting with an MTU of 1492 and an MRU of 1500, which would suggest that everything is setup pretty much correctly, but I don't know why its working one way and not the other.
I'm using the RB with a Technicolor TG582n, connected to ADSL which I had to reflash with a suitable image to make work (PITA!). I set up the bridge on the TG using no special options as recommended by someone else I spoke to that's made this work with a TG and a different router.
Any ideas of what is stopping the MTU go to 1492? Could it be anything to do with the MSS clamping that seems to automatically be added in to my mangle rules when I connect? Likewise, if I do manage to correct the MTU, will the clamping rules automatically disappear?
I've set the L2 MTU to 1600 or atleast 1530 (?) as recommended by some other posts that I managed to find on the subject. I'm not at home at the moment so can't check. What am I missing?
Thanks in advance!