Trying to connect to an NTT modem in Japan, which requires a low MTU for whatever reason. During PPP handshaking, despite telling my 2830 to use the lower MTU, it keeps trying to negotiate a higher one, and that terminates the handshaking.

How can I tell my 2830 to not be a dick.

PPP Start ()
PPP Closed : Remote Terminating ()

0:10:12 ISDN1>>>>PPPoE (WAN-2) Len = 10
Protocol:LCP(c021)
ConfReq Identifier:0x00
MRU: 1438 ##

0:10:12 ISDN1<<< Protocol:LCP(c021)
ConfReq Identifier:0xE5
MRU: 1438
Authentication Type:
CHAP 05
Magic Number: 0xa8788080 ##

0:10:12 ISDN1>>>>PPPoE (WAN-2) Len = 10
Protocol:LCP(c021)
ConfNak Identifier:0xE5
MRU: 1442 ##

0:10:12 ISDN1<<< Protocol:LCP(c021)
ConfAck Identifier:0x00
MRU: 1438 ##

0:10:12 ISDN1<<< Protocol:LCP(c021)
ConfReq Identifier:0xE6
MRU: 1438
Authentication Type:
CHAP 05
Magic Number: 0xa8788080 ##

0:10:12 ISDN1>>>>PPPoE (WAN-2) Len = 10
Protocol:LCP(c021)
ConfNak Identifier:0xE6
MRU: 1442 ##

0:10:12 ISDN1<<< Protocol:LCP(c021)
TermReq Identifier:0xE7 ##

0:10:12 ISDN1>>>>PPPoE (WAN-2) Len = 6
Protocol:LCP(c021)
TermAck Identifier:0xE7 ##



Starting a PPPoE session from a random Buffalo router here works fine, as does starting one from a PPPoE connection in OSX. The DrayTek is the only device that can't seem to handle it. It's on the latest firmware.

you can change the MTU in the command shell unless that it where you are already trying it

wan ppp_mru 2 1500 (or whar ever the value is you need) the 2 means wan2

Tried that. It sends an initial request out at that MRU. The NTT device comes back giving the terms, a new ID, with the same MRU, and then the DrayTek replies to those terms with a negative acknowledge offering a larger MTU that I didn't ask it to. Where on earth is the 1442 coming from?

wan mtu 1438
wan mtu 1438
wan ppp_mru 1 1438
wan ppp_mru 2 1438

All changed just in case, but somehow, it pulls 1442 out of thin air, meaning I can't use the router at all. It's an expensive WiFi access point at best now.

As I said, a cheap router here has no trouble connecting. Neither does my Mac creating its own PPPoE session.

Maybe something is being lost in translation, as I bet not too many DrayTek routers try to interface with NTT equipment, but even still, the fact two other devices manage fine suggests it's the DrayTek device that's not behaving as per the standards.