[EMAIL PROTECTED] writes: > >The mtu reported here is the same as that reported in 'ifconfig -a', > >i.e., the link-layer mtu. > > > > > > "ifconfig -a" reports the network layer MTU, not the link layer MTU > because (to repeat what everyone else says), ifconfig on Solaris > shows IP network interfaces, not anything else.
Correct. > I can shove 1536 bytes of garbage in a normal ethernet frame. > I can shove 1500 bytes of garbage in a normal IP packet. The first number isn't really defined anywhere. The actual number (from IEEE 802.3-2002 section 4.4.2) is 1518 for the maxUntaggedFrameSize, which is the payload plus the 14+4 Ethernet overhead, meaning 1500 octets total available for network layers. Per IEEE, the tag is separate from this number. It's not the MTU. Instead, MTU is an IP thing, defined in RFC 791. The MTU on IP is the overall frame size, including TCP/IP headers and user payload. In any event, I don't think MTU is at all ambiguous here. It's the IP MTU which happens to be equal to the maximum MAC client SDU on Ethernet. (Well, it needs to be _less_ or equal, but it's almost always equal.) Showing the 1518 number when everyone is expecting 1500 would be confusing and just plain weird. > If I want to capture an entire 1500 byte IP packet with snoop, > I have to specify "-s 1536". That's the snoop snaplen, which is not the MTU. -- James Carlson, Solaris Networking <[EMAIL PROTECTED]> Sun Microsystems / 1 Network Drive 71.232W Vox +1 781 442 2084 MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677 _______________________________________________ networking-discuss mailing list [email protected]
