If you look at the frame format for any LAN protocol you will see where the
Destination and Source MAC address are. You will not see these in any of the
WAN frame formats. I looked on CCO for more information to clarify this but
was unsuccessful. What I did look at was the frame formats for different WAN
protocols.
Here some links to show you what I am talking about:
SDLC
http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/sdlcetc.htm#xtocid2
49413
Frame Relay
http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/frame.htm#41825
X.25
http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/x25.htm#xtocid12273
10
Ethernet
http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/ethernet.htm#xtocid
118335
Token Ring
http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/tokenrng.htm#xtocid
73166
FDDI
http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/fddi.htm#xtocid1028
610
If you look at
http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/introwan.htm you
will see that where the WAN technologies lay in the OSI model and hopefully
this will also explain why serial lines don't have MAC addresses.
The reason that LAN protocols have a MAC address and WAN's don't is because
LAN's are contention based where WAN's are always full-duplex. Even though
layer 2 switching has been around for LAN's for a few years now the
protocols have stayed the same for backwards compatibility.
Neil
"John Green" <[EMAIL PROTECTED]> wrote in message
[EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> this post(s) was posted a couple of days back and just
> wanted some more list memebers to see if this correct
> before we take this as gospel truth.
> ---------------------------------------------------
> Neil Desai <[EMAIL PROTECTED]> wrote:
> > To my knowledge serial links don't have a MAC
> > address. Since most of them
> > are either a point-to-point or point-to-multipoint
> > there are some other type
> > of mappings. If a serial port needs a MAC address it
> > usuall uses one from
> > another interface that has one (i.e. ethernet).
> > Neil
> > ""Martinez, Carlos"" <[EMAIL PROTECTED]>
> > wrote in message
> >
> [EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> > > hello all,
> > >
> > > I had somebody ask me what the source mac address
> > would be on a frame sent
> > > across a serial link connected by to two routers,
> > > for example: Host A sends a packet to Host B,
> > which is on the other side
> > of
> > > the wan link. what would Host B see and what where
> > would he send his reply
> > > to.(the local router or Host A or what)????
> > >
> > > thanks in advance
> > >
> > > _________________________________
> > > FAQ, list archives, and subscription info:
> > http://www.groupstudy.com/list/cisco.html
> > > Report misconduct and Nondisclosure violations to
> > [EMAIL PROTECTED]
> > >
> >
> >
> > _________________________________
> > FAQ, list archives, and subscription info:
> > http://www.groupstudy.com/list/cisco.html
> > Report misconduct and Nondisclosure violations to
> [EMAIL PROTECTED]
>
>
> __________________________________________________
> Do You Yahoo!?
> Yahoo! Shopping - Thousands of Stores. Millions of Products.
> http://shopping.yahoo.com/
>
> _________________________________
> FAQ, list archives, and subscription info:
http://www.groupstudy.com/list/cisco.html
> Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
>
_________________________________
FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html
Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
