Single IP Address Assignment

I have several people from an ISP in one of a networking basics class.
We were discussing some of the basics of the IP protocol. We were
talking specifically about the process for leasing a block of IPs from
ICANN for use in a network. One of the students from the ISP mentioned
that their ISP leases to their DSL customers a single IP address for
use on the WAN side of the router. I was unsure how this ends up
working. He showed me the printout of the order and it shows a single
public IP being leased with a subnet mask of 255.255.255.255.

Usually for a routed connection, the subnet mask above indicates a host
device in a network, correct? So, is the ISP treating these customers
routers as part of one big network?

Confused and hoping someone can shed some light on the situation.

Keven

In article <1156985419.881638.110720@h48g2000cwc.googlegroups.com>,
[email]keven.denen@gmail.com[/email] wrote:
[color=blue]
> I have several people from an ISP in one of a networking basics class.
> We were discussing some of the basics of the IP protocol. We were
> talking specifically about the process for leasing a block of IPs from
> ICANN for use in a network. One of the students from the ISP mentioned
> that their ISP leases to their DSL customers a single IP address for
> use on the WAN side of the router. I was unsure how this ends up
> working. He showed me the printout of the order and it shows a single
> public IP being leased with a subnet mask of 255.255.255.255.
>
> Usually for a routed connection, the subnet mask above indicates a host
> device in a network, correct? So, is the ISP treating these customers
> routers as part of one big network?
>
> Confused and hoping someone can shed some light on the situation.
>
> Keven[/color]

What they probably do is assign a block of addresses to each DSLAM, so
the routing tables on their backbone only have to deal with these
aggregates. On the DSLAM itself there are presumably routes that
associate each IP with a particular DSL customer (a PPPoE username).

--
Barry Margolin, [email]barmar@alum.mit.edu[/email]
Arlington, MA
*** PLEASE post questions in newsgroups, not directly to me ***
*** PLEASE don't copy me on replies, I'll read them in the group ***

Hello,

[email]keven.denen@gmail.com[/email] a écrit :[color=blue]
> [...] One of the students from the ISP mentioned
> that their ISP leases to their DSL customers a single IP address for
> use on the WAN side of the router. I was unsure how this ends up
> working. He showed me the printout of the order and it shows a single
> public IP being leased with a subnet mask of 255.255.255.255.
>
> Usually for a routed connection, the subnet mask above indicates a host
> device in a network, correct? So, is the ISP treating these customers
> routers as part of one big network?[/color]

A /32 mask usually indicates a point to point link, which is rather
common on DSL lines using some form of PPP.