Are you authenticating with PPPoE? If so, it has a maximum MTU size of 1492 due to the encapsulation overhead.
--- Tom Pipes T6 Broadband/ Essex Telcom Inc [email protected] ----- Original Message ----- From: "William Herrin" <[email protected]> To: "Deric Kwok" <[email protected]> Cc: "nanog list" <[email protected]> Sent: Thursday, June 17, 2010 8:36:00 AM Subject: Re: pls help about mtu setting On Thu, Jun 17, 2010 at 8:19 AM, Deric Kwok <[email protected]> wrote: > My DSL company asks me to set the modem 146 2 and my old company used 14 92 > Why it is not standard 1 500? Because they're wrapping your packet inside another packet that they then transmit on a line with a 1500 byte MTU. The header on their packet needs a few bytes, so you can't have them. Regards, Bill Herrin -- William D. Herrin ................ [email protected] [email protected] 3005 Crane Dr. ...................... Web: <http://bill.herrin.us/> Falls Church, VA 22042-3004
