Chuck wrote:
> 
> recall that the link between you and whomever is a two host
> network. 

And I would add to that, recall that the link is just a transit for
end-to-end traffic. With the exception of network management, it doesn't
matter what the network-layer addressing is on that link. It carries
host-to-host traffic which is identified by the network-layer addresses of
the end hosts.

What I'm trying to get at is that you may be concerned because of a common
misconception that the network-layer addressing changes from hop-to-hop,
which it doesn't. (If you're studying for CCIE, then of course you wouldn't
have that micsonception, but I don't know how far you are in your studies
yet. :-)

Now, network management is a concern, however. If your serial interface is
unnumbered, you can't ping it or send it SNMP messages. With those
functions, the serial port acts as an end host and must have a network-layer
address. That's the tradeoff. As Chuck says, it's common practice to use
unnumbered with static and default routing pointing to the interface,
however. So many people take the tradeoff. Even though you can't ping the
serial interface, you can still get a lot of info from it with the show
interface command.

________________________

Priscilla Oppenheimer
http://www.priscilla.com



> if you
> were numbering, you would most likely use a /30. even when
> connecting to the
> internet, this link need not use public IP space. Your ISP is
> most likely
> using a static route to you, and you in turn are using a static
> route to
> them.
> 
> them: ip route "your public space" out interface X
> 
> You: ip route 0.0.0.0 0.0.0.0 interface Y
> 
> this is a regular practice.
> 
> IP unnumbered is even better, because then no one has to commit
> to or agree
> upon address, and no one has to waste public space.
> 
> Usually, you would number your ethernet port with a public
> number, and you
> would use an ip unnumbered off that publicly addressed
> interface.
> 
> HTH
> 
> 
> 
> ""richard dumoulin""  wrote in message
> [EMAIL PROTECTED]">news:[EMAIL PROTECTED]...
> > Hey guys,
> > I have to connect a Cisco router to the internet (Worldcom)
> and I was told
> > the following "If your router is a CISCO model, then there is
> no
> > need to assign actual IP addresses to the WAN serial
> > interfaces since CISCO's un-numbered technology can
> > be employed". Does this mean that I can configure IP
> unnumbered ethernet0
> or
> > loopback0 (with one of them having a routable IP address) and
> so I must
> > configure ppp encap on the serial ??
> >
> > I am a bit confused, thx for your help !!
> 
> 




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