[LARTC] Unnumbered

[LARTC] Unnumbered

[M.F. PSIkappa]

Hi,
it's posibility to make something similar to Cisco unnumber on Linux ?
E. g.
interface Serial0
 ip unnumbered Ethernet0
I don't want to assign to interface private IP.

PSIkappa
psi@atlantis.sk


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Re: [LARTC] Unnumbered

[Arthur van Leeuwen]

On Fri, 22 Jun 2001, M.F. PSIkappa wrote:


> it's posibility to make something similar to Cisco unnumber on Linux ?
> E. g.
> interface Serial0
>  ip unnumbered Ethernet0
> I don't want to assign to interface private IP.

If I understand the ip unnumbered command correctly it allows you to share a
single IP address on multiple interfaces. This is trivial on Linux: just add
the same IP address to each of the interfaces with  ip addr add

The routing effects I cannot correctly comment on, as I'm not sufficiently
versed in IOS to fully grasp the effects of  ip unnumbered

Doei, Arthur.

-- 
  /\    / |      arthurvl@sci.kun.nl      | Work like you don't need the money
 /__\  /  | A friend is someone with whom | Love like you have never been hurt
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Re: [LARTC] Unnumbered

[M.F. PSIkappa]

On Fri, 22 Jun 2001, Arthur van Leeuwen wrote:

> On Fri, 22 Jun 2001, M.F. PSIkappa wrote:
> 
> 
> > it's posibility to make something similar to Cisco unnumber on Linux ?
> > E. g.
> > interface Serial0
> >  ip unnumbered Ethernet0
> > I don't want to assign to interface private IP.
> 
> If I understand the ip unnumbered command correctly it allows you to share a
> single IP address on multiple interfaces. This is trivial on Linux: just add
> the same IP address to each of the interfaces with  ip addr add
> 
> The routing effects I cannot correctly comment on, as I'm not sufficiently
> versed in IOS to fully grasp the effects of  ip unnumbered

No, it's incorrect, unnumberd allow you to connect 2 router without IP
adresses.

192.168.0.1/24 [cisco]unnumbered-----unnumberd[cisco] 192.168.2.1/24

It's special case of point-to-point connection. In linux if I make
point-to-point connection I have to assign any IP on both endpoint of
connection.

> Doei, Arthur.

PSIkappa
psi@atlantis.sk


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Re: [LARTC] Unnumbered

[Arthur van Leeuwen]

On Fri, 22 Jun 2001, M.F. PSIkappa wrote:

> On Fri, 22 Jun 2001, Arthur van Leeuwen wrote:
>
> > On Fri, 22 Jun 2001, M.F. PSIkappa wrote:
> >
> >
> > > it's posibility to make something similar to Cisco unnumber on Linux ?
> > > E. g.
> > > interface Serial0
> > >  ip unnumbered Ethernet0
> > > I don't want to assign to interface private IP.
> >
> > If I understand the ip unnumbered command correctly it allows you to share a
> > single IP address on multiple interfaces. This is trivial on Linux: just add
> > the same IP address to each of the interfaces with  ip addr add
> >
> > The routing effects I cannot correctly comment on, as I'm not sufficiently
> > versed in IOS to fully grasp the effects of  ip unnumbered
>
> No, it's incorrect, unnumberd allow you to connect 2 router without IP
> adresses.
>
> 192.168.0.1/24 [cisco]unnumbered-----unnumberd[cisco] 192.168.2.1/24
>
> It's special case of point-to-point connection. In linux if I make
> point-to-point connection I have to assign any IP on both endpoint of
> connection.

What is the difference with

192.168.0.1/24 [linux] 192.168.0.1 ------- 192.168.2.1 [linux] 192.168.2.1/24

if I may be so bold to ask? Yes, the routing effects may be different, and I
mentioned that might be a problem, but the unnumbered thing looks like a
cisco-specific hack...

Doei, Arthur.

-- 
  /\    / |      arthurvl@sci.kun.nl      | Work like you don't need the money
 /__\  /  | A friend is someone with whom | Love like you have never been hurt
/    \/__ | you can dare to be yourself   | Dance like there's nobody watching


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Re: [LARTC] Unnumbered

[M.F. PSIkappa]

On Fri, 22 Jun 2001, Arthur van Leeuwen wrote:

> > > > it's posibility to make something similar to Cisco unnumber on Linux ?
> > > > E. g.
> > > > interface Serial0
> > > >  ip unnumbered Ethernet0
> > > > I don't want to assign to interface private IP.
> > >
> > > If I understand the ip unnumbered command correctly it allows you to share a
> > > single IP address on multiple interfaces. This is trivial on Linux: just add
> > > the same IP address to each of the interfaces with  ip addr add
> > >
> > > The routing effects I cannot correctly comment on, as I'm not sufficiently
> > > versed in IOS to fully grasp the effects of  ip unnumbered
> >
> > No, it's incorrect, unnumberd allow you to connect 2 router without IP
> > adresses.
> >
> > 192.168.0.1/24 [cisco]unnumbered-----unnumberd[cisco] 192.168.2.1/24
> >
> > It's special case of point-to-point connection. In linux if I make
> > point-to-point connection I have to assign any IP on both endpoint of
> > connection.
> 
> What is the difference with
> 
> 192.168.0.1/24 [linux] 192.168.0.1 ------- 192.168.2.1 [linux] 192.168.2.1/24
> 
> if I may be so bold to ask? Yes, the routing effects may be different, and I
> mentioned that might be a problem, but the unnumbered thing looks like a
> cisco-specific hack...

Difference is in traceroute. Unnumbered is invisible, if I assign IP I see
it in traceroute, but I can make hack that make this connection invisible,
but it's rfc break ...

Yes, it's cisco specific hack.
 
> Doei, Arthur.

PSIkappa
psi@atlantis.sk


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Re: [LARTC] Unnumbered

[Jasper Spaans]

On Fri, Jun 22, 2001 at 10:31:04AM +0200, M.F. PSIkappa wrote:

> > The routing effects I cannot correctly comment on, as I'm not sufficiently
> > versed in IOS to fully grasp the effects of  ip unnumbered
> 
> No, it's incorrect, unnumberd allow you to connect 2 router without IP
> adresses.
> 
> 192.168.0.1/24 [cisco]unnumbered-----unnumberd[cisco] 192.168.2.1/24
> 
> It's special case of point-to-point connection. In linux if I make
> point-to-point connection I have to assign any IP on both endpoint of
> connection.

So, in effect, you're changing the behaviour of your (level 3) port to a
level 2 port, i.e., a switch, and add some filtering features to it, or am I
missing something?

In that case, you might get away by configuring the two pairs of ports as
ethernet bridge ports, and only assign IP-addresses to the two outer
interfaces as in the diagram above.

Not sure whether all shaping and firewalling tricks will work in that case
though. Anyone got a comment on that?

Regards,
-- 
  Q_.           Jasper Spaans <j@sp3r.net>
 `~\            http://jsp.ds9a.nl/
Mr /\           Tel/Fax: +31-84-8749842
Zap             Move '.sig' for great justice!

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Re: [LARTC] Unnumbered

[Dmytro O. Redchuk]

On Fri, Jun 22, 2001 at 10:34:37AM +0200, Arthur van Leeuwen wrote:
> On Fri, 22 Jun 2001, M.F. PSIkappa wrote:
> 
> > On Fri, 22 Jun 2001, Arthur van Leeuwen wrote:
> >
> > > On Fri, 22 Jun 2001, M.F. PSIkappa wrote:
> > >
> > >
> > > > it's posibility to make something similar to Cisco unnumber on Linux ?
> > > > E. g.
> > > > interface Serial0
> > > >  ip unnumbered Ethernet0
> > > > I don't want to assign to interface private IP.
> > >
> > > If I understand the ip unnumbered command correctly it allows you to share a
> > > single IP address on multiple interfaces. This is trivial on Linux: just add
> > > the same IP address to each of the interfaces with  ip addr add
> > >
> > > The routing effects I cannot correctly comment on, as I'm not sufficiently
> > > versed in IOS to fully grasp the effects of  ip unnumbered
> >
> > No, it's incorrect, unnumberd allow you to connect 2 router without IP
> > adresses.
> >
> > 192.168.0.1/24 [cisco]unnumbered-----unnumberd[cisco] 192.168.2.1/24
> >
> > It's special case of point-to-point connection. In linux if I make
> > point-to-point connection I have to assign any IP on both endpoint of
> > connection.
> 
> What is the difference with
> 
> 192.168.0.1/24 [linux] 192.168.0.1 ------- 192.168.2.1 [linux] 192.168.2.1/24
> 
> if I may be so bold to ask? Yes, the routing effects may be different, and I
> mentioned that might be a problem, but the unnumbered thing looks like a
> cisco-specific hack...

Sorry, it doesnt look so -- as far as i know unnumbered interfaces (PtoP connections) are supported by a number of vendors.
Having a possibility to create unnumbered links under Linux would be nice, imho.

> 
> Doei, Arthur.
> 
> -- 
>   /\    / |      arthurvl@sci.kun.nl      | Work like you don't need the money
>  /__\  /  | A friend is someone with whom | Love like you have never been hurt
> /    \/__ | you can dare to be yourself   | Dance like there's nobody watching
> 
> 
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> http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://ds9a.nl/2.4Routing/

-- 
Dmytro O. Redchuk                 http://www.popnet.kiev.ua
System Administrator              Phone: (380).44.495.26.05
PopNet Kommunikation Kiew         Fax  : (380).44.495.26.02


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Re: [LARTC] Unnumbered

[Arthur van Leeuwen]

On Fri, 22 Jun 2001, M.F. PSIkappa wrote:

> On Fri, 22 Jun 2001, Arthur van Leeuwen wrote:
>
> > > > > it's posibility to make something similar to Cisco unnumber on Linux ?
> > > > > E. g.
> > > > > interface Serial0
> > > > >  ip unnumbered Ethernet0
> > > > > I don't want to assign to interface private IP.
> > > >
> > > > If I understand the ip unnumbered command correctly it allows you to share a
> > > > single IP address on multiple interfaces. This is trivial on Linux: just add
> > > > the same IP address to each of the interfaces with  ip addr add
> > > >
> > > > The routing effects I cannot correctly comment on, as I'm not sufficiently
> > > > versed in IOS to fully grasp the effects of  ip unnumbered
> > >
> > > No, it's incorrect, unnumberd allow you to connect 2 router without IP
> > > adresses.
> > >
> > > 192.168.0.1/24 [cisco]unnumbered-----unnumberd[cisco] 192.168.2.1/24
> > >
> > > It's special case of point-to-point connection. In linux if I make
> > > point-to-point connection I have to assign any IP on both endpoint of
> > > connection.
> >
> > What is the difference with
> >
> > 192.168.0.1/24 [linux] 192.168.0.1 ------- 192.168.2.1 [linux] 192.168.2.1/24
> >
> > if I may be so bold to ask? Yes, the routing effects may be different, and I
> > mentioned that might be a problem, but the unnumbered thing looks like a
> > cisco-specific hack...
>
> Difference is in traceroute. Unnumbered is invisible, if I assign IP I see
> it in traceroute, but I can make hack that make this connection invisible,
> but it's rfc break ...

Ah, but iptable's mangle module will let you play around with the TTL field
of packets being forwarded through a linux box. Yes, it takes some more
configuring, but the behaviour can be duplicated. And that is not considered
a hack. Besides, ever heard of masquerading? That is nowhere near RFC
compliance... and should theoretically be impossible, if I'm to believe
Jos Vos (one of the first implementers).

Doei, Arthur.

-- 
  /\    / |      arthurvl@sci.kun.nl      | Work like you don't need the money
 /__\  /  | A friend is someone with whom | Love like you have never been hurt
/    \/__ | you can dare to be yourself   | Dance like there's nobody watching


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Re: [LARTC] Unnumbered

[Greg Varga]

On Fri, 22 Jun 2001 10:55:41 +0200 (CEST), M.F. PSIkappa wrote:

>> > No, it's incorrect, unnumberd allow you to connect 2 router without IP
>> > adresses.
>> >
>> > 192.168.0.1/24 [cisco]unnumbered-----unnumberd[cisco] 192.168.2.1/24
>> >
>> > It's special case of point-to-point connection. In linux if I make
>> > point-to-point connection I have to assign any IP on both endpoint of
>> > connection.
>> 
>> What is the difference with
>> 
>> 192.168.0.1/24 [linux] 192.168.0.1 ------- 192.168.2.1 [linux] 192.168.2.1/24
>> 
>> if I may be so bold to ask? Yes, the routing effects may be different, and I
>> mentioned that might be a problem, but the unnumbered thing looks like a
>> cisco-specific hack...
>
>Difference is in traceroute. Unnumbered is invisible, if I assign IP I see
>it in traceroute, but I can make hack that make this connection invisible,
>but it's rfc break ...

This is correct, in the workings... But I don't think it really breaks
the RFC's...

Anyways this is the diffrence:

All networks prefixed with "10.0"...

Numbered:
----- 10.0.1.1/24 [[[Linux Box]]] 10.0.0.100/24  -----Ethernet-----
10.0.2.1/24 [[[Linux Box]]] 10.0.0.200/24 -----

Unnumbered:
----- 10.0.1.1/24 [[[Linux Box]]]  -----P to P-----  [[[Linux Box]]]
10.0.0.200/24 -----

As you can see, the unnumbered is a Point to Point connection, and acts
more like a "bridge"...

Actually, if you want to do an Unnumbered connection with two Ethernet
Interfaces, thats exactly how I would set it up... as a Bridge.  Either
that or use PPPoE and that should be able to do something simular.

>Yes, it's cisco specific hack.

No this is not true...  Alot of the Point to Point (IE: Dial-Up, ISDN)
type Internet Connections use Unnumbered Connections.  There are a
large number of companies that support these type of connections.

--Greg.
-------------------------------------
Greg Varga
Owner: Digital Realities
  http://www.digital.realities.com
  604.576.2219
Lead Programmer of MUTAG
  http://www.bvcompuworks.com/mutag
Network Administrator
-------------------------------------



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Re: [LARTC] Unnumbered

[Ramin Alidousti]

On Fri, Jun 22, 2001 at 09:37:29AM -0700, Greg Varga wrote:

> This is correct, in the workings... But I don't think it really breaks
> the RFC's...

It has nothing to do with the RFC's.

> 
> Anyways this is the diffrence:
> 
> All networks prefixed with "10.0"...
> 
> Numbered:
> ----- 10.0.1.1/24 [[[Linux Box]]] 10.0.0.100/24  -----Ethernet-----
> 10.0.2.1/24 [[[Linux Box]]] 10.0.0.200/24 -----
> 
> Unnumbered:
> ----- 10.0.1.1/24 [[[Linux Box]]]  -----P to P-----  [[[Linux Box]]]
> 10.0.0.200/24 -----
> 
> As you can see, the unnumbered is a Point to Point connection, and acts
> more like a "bridge"...
> 
> Actually, if you want to do an Unnumbered connection with two Ethernet
> Interfaces, thats exactly how I would set it up... as a Bridge.  Either
> that or use PPPoE and that should be able to do something simular.
> 
> >Yes, it's cisco specific hack.
> 
> No this is not true...  Alot of the Point to Point (IE: Dial-Up, ISDN)
> type Internet Connections use Unnumbered Connections.  There are a
> large number of companies that support these type of connections.

You are correct, Greg. Unnumbered interfaces are (mostly) ptp interfaces.
When setting up a ptp interface you should usually use one /30 in a
traditional way. Now, for a ptp connection there is only one IP entity
at the other end and it doesn't have to be one out of a /30. Any IP
address will do. That's why they usually use the loopback IP (or the
IP of another interface) to identify the Unnumbered interface.

I'm not sure how this can be done with linux. But I think that pppd
program does not require you to waste one /30 for the link. The server
side can send one /32 to the client side and announce another IP (eg,
the IP of its ethernet interface) as the peer IP of the ppp link. At
least this is what's happening when you dial in to a NAS.

Ramin

> 
> --Greg.

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