Subject: (usr-tc) Three IPs on a dialup?

From: Stephen Amadei <[email-masked]>
Date: Wed, 24 Nov 1999 09:13:51 +0000

Hi ya guys... I have a customer who wants three IPs on a dialup.

I am thinking this cannot be done with a dialup on a USR TC, Hiper
or not, but in an attempt to satisify my morbid sense of trivia...

How can a dialup line be set up with three IP addreses routed over it?

Needless to say, I suggested they use NAT...  

Anyway, thanks in advance...

					----Steve
Stephen Amadei
Director of MIS
Dandy Connections, Inc.
Atlantic City, NJ

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From: Mike Andrews <[email-masked]>
Date: Wed, 24 Nov 1999 09:18:39 +0000

Route a /29 subnet to them, which is the smallest block that'll give them
at least 3 usable addresses.  (8 addresses, 6 usable.)

Mike Andrews (MA12) * [email-masked] * http://www.bit0.com/
VP, sysadmin, & network guy, Digital Crescent Inc, Frankfort KY
Internet services for Frankfort, Lawrenceburg, Owenton, & Shelbyville
"With sufficient thrust, pigs fly just fine." -- RFC 1925

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From: Stephen Amadei <[email-masked]>
Date: Wed, 24 Nov 1999 11:35:32 +0000

> at least 3 usable addresses.  (8 addresses, 6 usable.)

O.K... I guess I can do this through RADIUS, right?

Now, subnetting below /24 has always been a weak point for me... and I
realise I'm going a bit off topic, but I figure everyone on this list are
about as knowledgable in subnetting as I'm going to find.  

I understand the basic tables of subnets and masks for under a class C.
But I have two questions on how to use them.

First, lets say I give this dialup a network of 192.168.1.0/29
(assuming 192.168.1.0/24 is a normal, routable class C).  The
net number is .0 and the broadcast is .7.  What I don't understand
next is what to do with the rest of the addresses.  Can I dump the rest of
the addresses onto an existing segment of my network that currently has 
a class C on it?  Would I do it like the following?

   Internet----Router(200.200.200.1)
                   |
             ____________
             Main Network
             200.200.200.0/24
             192.168.1.8/29
             192.168.1.16/28
             192.168.1.32/27
             192.168.1.64/26
             192.168.1.128/25
             ____________
                   |
             ____________
             Total Control
             (normally gives out IPs from a pool in 200.200.200.0/24
             Gives out a 192.168.1.0/29
             ____________

Next, I don't quite understand where I need to apply static routes.
I assume I would need to add a static route on the TC for the subnet I
give the dialup, but would that subnet also require a routing entry on my
router, except for the obvious need for a 192.168.1.0/24 route?

Confused... but thanx in advance...

					----Steve
Stephen Amadei
Director of MIS
Dandy Connections, Inc.
Atlantic City, NJ

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From: Ed <[email-masked]>
Date: Wed, 24 Nov 1999 16:46:23 +0000

It they did a /30 that would give 2 usable and then the static IP to route to would be the third.

As long as they don't have 3 seperate boxes to put behind it.

Ed Taylor

----- Original Message ----- 
  From: Stephen Amadei 
  To: [email-masked] 
  Sent: Wednesday, November 24, 1999 4:32 AM
  Subject: Re: (usr-tc) Three IPs on a dialup?

  ----Steve
  Stephen Amadei
  Director of MIS
  Dandy Connections, Inc.
  Atlantic City, NJ

  -

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From: Jeff Mcadams <[email-masked]>
Date: Wed, 24 Nov 1999 16:52:04 +0000

Thus spake Ed

>As long as they don't have 3 seperate boxes to put behind it.

Problem being...with typical routing setup, you've got one of two
scenarios...either the eth0 of the routing box is the static that's
assigned "to route to" (using your terminology to help clarify here).
Meaning that the static is pulled out of the /30 block, meaning there's
only one other address available...one short...

Or, you have the static IP "to route to" :), and then the /30 block has
to have one of the IP's assigned to the eth0 of the same box doing the
routing which means you've got two IP's assigned to the same box...still
one short.  :/

You could do a couple of /30's and have multiple IP's assigned to the
eth0 card of the router....but then you're still chewing up the same
amount of space as a single /29 does with fewer useable addresses...it
does have the upside of letting you assign non-contiguous addresses if
your IP space is that fragmented.
-- 
Jeff McAdams                            Email: [email-masked]
Head Network Administrator              Voice: (502) 966-3848
IgLou Internet Services                        (800) 436-4456

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From: Ed <[email-masked]>
Date: Wed, 24 Nov 1999 17:00:23 +0000

Yes as I stated... 

"As long as they don't have 3 seperate boxes to put behind it." but I should have said to clarify if you have but 1 box on the other side. This would be 2 IP's on the main box which is directly connected and 1 IP on the other.

Ed Taylor

----- Original Message ----- 
  From: Jeff Mcadams 
  To: [email-masked] 
  Sent: Wednesday, November 24, 1999 9:49 AM
  Subject: Re: (usr-tc) Three IPs on a dialup?

  Thus spake Ed

  -

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From: Mike Andrews <[email-masked]>
Date: Wed, 24 Nov 1999 19:17:24 +0000

> O.K... I guess I can do this through RADIUS, right?

Yeah.  Where you'd normally have

	Framed-IP-Address = 255.255.255.254,
	Framed-IP-Netmask = 255.255.255.255,

you'd put instead something like this:

	Framed-IP-Address = 192.168.1.0,
	Framed-IP-Netmask = 255.255.255.248,

>    Internet----Router(200.200.200.1)

Looks fairly reasonable.  You don't *have* to shove all those extra blocks
onto a single LAN though...  you don't have to shove 'em anywhere if you
aren't really using them yet.  Just save them for when you get some
dedicated T1 customers that need some smallish blocks of IP space.

> router, except for the obvious need for a 192.168.1.0/24 route?

If you're running RIPv2 or OSPF, and have it set up right, you shouldn't
need ANY static routes.  If you've got 2 or 3 TC's handling the same
dialup pool (say for example you had 20 PRI's at one POP)...  then static
routes on your TC or your upstream are kinda useless because you don't
know which TC they're going to hit on any given day/hour/whatever...  so
you really can't use static routes there anyway.

When your 192.168.0.9/29 user dials in, the route gets added to the TC's
routing table automatically (when it's told the route by Radius,
basically).  So that part you don't have to worry about at all.  Then it's
up to RIPv2 or OSPF to advertise that route to the rest of your network,
and to drop the announcement when they hang up.

Your regular IP pools are supposed to be advertised the same way, but in
practice I never really got it working with RIPv2.  (To be honest I didn't
really TRY very hard. :)  With OSPF it works great though.  Just add the
pool and all the Ciscos see it automatically.  Delete a pool and the
Ciscos drop that too.

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