Zsombor Papp wrote: > > At 04:44 PM 6/26/2003 +0000, Priscilla Oppenheimer wrote: > > > In fact I seem to remember that you *had* to specify it on > a > > subinterface level > > > for a while, and it was in fact the encapsulation type that > selected the > > > subinterface. The reason for this behavior is that > "Ethernet" has two > > > sub-layers within Layer 2, so even there you have an > implied encapsulation > > > assigned to the physical interface (the lower of the two > > sub-layers, the IEEE > > > 802.3/Ethernet II format), and only the higher layer (layer > 802.2) > > > encapsulation is assigned to a subinterface. > > > >You can't tell an Ethernet interface to use 802.2 except > within the IPX > >network commands. Maybe you're thinking of the 802.1Q VLAN > tagging standard. > > No, I am thinking about the IPX case. Using multiple different > encapsulations on a single physical interface used to be a > typical question > in the CCIE lab, that's why I remember it. I've never had to > use it ever > since, so I might have said something incorrectly, but I don't > see what > that was.
Oh. Your message didn't say anything about IPX. Also, this was a weird analogy that doesn't quite work: "only the higher layer (layer 802.2) encapsulation is assigned to a subinterface." Ethernet II doesn't have 802.2. Neither does novell-ether. IPX can use either of those, as well as 802.3 with 802.2 and 802.3 with 802.2 and SNAP. > I quickly looked at this page: > > http://www.cisco.com/univercd/cc/td/doc/product/software/ios111/mods/4mod/4cbook/4cipx.htm > > and I think it confirmed what I said (search for "subinterface" > within the > page), but I wouldn't mind to be corrected. > > >Ethernet encapsulation behavior isn't much like encapsulation > on serial > >interfaces, which can only be one of the major categories: > HDLC, PPP, Frame > >Relay. But Frame Relay has 2 varieties. > > I think I am missing the point here. Obviously they aren't the > same, > otherwise it would be foolish to give them such different names > :), but I > do think that the Ethernet encapsulations play a very similar > role to the > serial encapsulations (only in a different situation). Ethernet encapsulation depends on the payload. IP uses Ethernet II, CDP uses SNAP, etc. With the exception of IPX, it's not configurable. (Actually ARP is configurable too for historical reasons. Long story that I can't get into now). That's not like encapsulation on a serial interface that doesn't care about the upper layer. Think about the IOS software. It has to know what it is encapsulating on Ethernet. It doesn't on a serial interface. That was what I meant by the behavior being different. Priscilla > > If you mean that the original question was very Frame Relay and > Cisco IOS > implementation specific, and compared to that my answer was too > generic and > theoretical, then you are probably right. :) > > Thanks, > > Zsombor > > Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=71488&t=71421 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
