Is there an IP address which represents "no default gateway?"

Just a quick question for you networking wizards out there:

I am trying to configure a TCP/IP-based network printer. This printer
will reside on an isolated network so a default gateway is not
needed. The network configuration of this printer is accomplished via
HTTP through a standard web interface. Although I do not want to
specify a default gateway, the printer's configuration does not allow
me to leave the "default gateway:" field blank. Is there an ip
address I can enter that will be interpreted as "no default gateway?"
is 0.0.0.0 a valid input? If so, what does it mean? Thanks in
advance for any insight on this one.

(E-Mail Removed) writes:

[...]

> Although I do not want to specify a default gateway, the printer's
> configuration does not allow me to leave the "default gateway:"
> field blank. Is there an ip address I can enter that will be
> interpreted as "no default gateway?" is 0.0.0.0 a valid input? If
> so, what does it mean?

0.0.0.0 means "this host, this network", so it's essentially telling
the printer to use itself as its default gateway (though it may
interpret that differently).

I would suggest using an address on your network that is and will
remain unused.

-----Scott.

Thanks for the info. My initial guess was that 0.0.0.0 represented a
null address but it sound like it has a much different meaning. I'll
play around with this setting and see what works. I'm surprised that
the configuration will not allow me to leave the default gateway
undefined.

> 0.0.0.0 means "this host, this network", so it's essentially telling
> the printer to use itself as its default gateway (though it may
> interpret that differently).
>
> I would suggest using an address on your network that is and will
> remain unused.

> Just a quick question for you networking wizards out there:
> I am trying to configure a TCP/IP-based network printer. This printer
> will reside on an isolated network so a default gateway is not
> needed. The network configuration of this printer is accomplished via
> HTTP through a standard web interface. Although I do not want to
> specify a default gateway, the printer's configuration does not allow
> me to leave the "default gateway:" field blank. Is there an ip
> address I can enter that will be interpreted as "no default gateway?"
> is 0.0.0.0 a valid input? If so, what does it mean? Thanks in
> advance for any insight on this one.

Why not use 127.0.0.1 ?


Stefan

Stefan Monnier <(E-Mail Removed)> writes:

[...]
>> I do not want to specify a default gateway, the printer's
>> configuration does not allow me to leave the "default gateway:"
>> field blank. Is there an ip address I can enter that will be
>> interpreted as "no default gateway?"
[...]
> Why not use 127.0.0.1 ?

There's a potential for that to cause a nasty loop, and for each
packet sent from the printer to be processed many times, until it
times out or reaches its maximum hops. Then when the ICMP Time
Exceeded message is sent, that could loop too. And all of this
assumes the printer handles timeout correctly, which it might not;
they could loop forever!

Of course, the printer might be smart enough to detect this and
discard the packets rather than sending them to itself, but probably
if it were well-designed it would have an option to put in no default
route. :-)

----Scott.

>>> I do not want to specify a default gateway, the printer's
>>> configuration does not allow me to leave the "default gateway:"
>>> field blank. Is there an ip address I can enter that will be
>>> interpreted as "no default gateway?"
> [...]
>> Why not use 127.0.0.1 ?

> There's a potential for that to cause a nasty loop, and for each
> packet sent from the printer to be processed many times, until it
> times out or reaches its maximum hops. Then when the ICMP Time
> Exceeded message is sent, that could loop too. And all of this
> assumes the printer handles timeout correctly, which it might not;
> they could loop forever!

> Of course, the printer might be smart enough to detect this and
> discard the packets rather than sending them to itself, but probably
> if it were well-designed it would have an option to put in no default
> route. :-)

It's expensive to write a new TCP/IP stack, so the printer most likely uses
some off-the-shelf TCP/IP stack which should work just fine.

As a matter of fact, even if the stack is really stupid and does end up
sending packets to itself, the "looping" shouldn't cause any problem.


Stefan

Hello,

Scott Gifford a écrit :
>
>>Why not use 127.0.0.1 ?
>
> There's a potential for that to cause a nasty loop

Unless the printer TCP/IP stack acts as a router, which a printer has no
reason to do, I do not see how there could be a loop.

, and for each
> packet sent from the printer to be processed many times, until it
> times out or reaches its maximum hops. Then when the ICMP Time
> Exceeded message is sent, that could loop too.

Nope, an ICMP error would be sent to the own printer address (source
address of the original packet that caused the error) and would be
received immediately without any loop.

[Followup-To: comp.protocols.tcp-ip, no Linux in this thread so far]

Stefan Monnier <(E-Mail Removed)> writes:

>>>> I do not want to specify a default gateway, the printer's
>>>> configuration does not allow me to leave the "default gateway:"
>>>> field blank. Is there an ip address I can enter that will be
>>>> interpreted as "no default gateway?"
>> [...]
>>> Why not use 127.0.0.1 ?
>
>> There's a potential for that to cause a nasty loop
[...]

> It's expensive to write a new TCP/IP stack, so the printer most likely uses
> some off-the-shelf TCP/IP stack which should work just fine.

That's a good point, although it would be difficult to find out the
implementation details, and very difficult to test its internal
routing behavior .

> As a matter of fact, even if the stack is really stupid and does end up
> sending packets to itself, the "looping" shouldn't cause any problem.

Well, it depends on how efficiently it processes packets, how much
processing power it has, and how frequently it sends packets out.

I would still recommend against this configuration unless it's
documented to work by the manufacturer.

----Scott.

Scott Gifford <(E-Mail Removed)> writes:

>Stefan Monnier <(E-Mail Removed)> writes:

>[...]
>>> I do not want to specify a default gateway, the printer's
>>> configuration does not allow me to leave the "default gateway:"
>>> field blank. Is there an ip address I can enter that will be
>>> interpreted as "no default gateway?"

What "configuration"
You could try having the address itself be the gateway.
Is this where you enter the IP of the printer or the IP of the host
connected to the printer?


>[...]
>> Why not use 127.0.0.1 ?

>There's a potential for that to cause a nasty loop, and for each
>packet sent from the printer to be processed many times, until it
>times out or reaches its maximum hops. Then when the ICMP Time
>Exceeded message is sent, that could loop too. And all of this
>assumes the printer handles timeout correctly, which it might not;
>they could loop forever!

>Of course, the printer might be smart enough to detect this and
>discard the packets rather than sending them to itself, but probably
>if it were well-designed it would have an option to put in no default
>route. :-)

>----Scott.