[gentoo-user] [OT] Pinging two devices on the same IP address

[gentoo-user] [OT] Pinging two devices on the same IP address

[Mick]

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Hi All,

I am trying to troubleshoot two devices both behind the same IP address:

Device A:  a router
Device B:  a wireless access point

The network looks like this:

Internet >> modem >> router >> AP

Currently I have set up a firewall rule in the router to forward all pings to 
the AP.  The logic is that if the ping returns then both router and AP are 
up.

That's alright when both devices are working.  However, if I am interested to 
know which one of the two has failed, a different system is needed.  Any idea 
how I could ping them both separately?  Is there a clever firewall rule I 
could concoct?
-- 
Regards,
Mick

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Re: [gentoo-user] [OT] Pinging two devices on the same IP address

[Daniel da Veiga]

On 10/23/07, Mick <michaelkintzios@gmail.com> wrote:
> Hi All,
>
> I am trying to troubleshoot two devices both behind the same IP address:
>
> Device A:  a router
> Device B:  a wireless access point
>
> The network looks like this:
>
> Internet >> modem >> router >> AP
>
> Currently I have set up a firewall rule in the router to forward all pings to
> the AP.  The logic is that if the ping returns then both router and AP are
> up.
>
> That's alright when both devices are working.  However, if I am interested to
> know which one of the two has failed, a different system is needed.  Any idea
> how I could ping them both separately?  Is there a clever firewall rule I
> could concoct?

I really don't get how you forward something to an Access Point, isn't
this device like a "dumb hub" on your wireless network? Mine doesn't
have an IP, nor MAC or anything that could identify it on the network.

I would also be interested if something like that is possible...

-- 
Daniel da Veiga

Filosofia de TI: Programadores de verdade consideram o conceito "o que
você vê é o que você tem" tão ruim em editores de texto quanto em
mulheres. Não, o programador de verdade quer um editor de texto do
estilo "você pediu, você levou" - complicado, indecifrável, poderoso,
impiedoso, perigoso.
--
gentoo-user@gentoo.org mailing list

Re: [gentoo-user] [OT] Pinging two devices on the same IP address

[Dan Farrell]

On Tue, 23 Oct 2007 18:27:10 -0300
"Daniel da Veiga" <danieldaveiga@gmail.com> wrote:

> I really don't get how you forward something to an Access Point, isn't
> this device like a "dumb hub" on your wireless network? Mine doesn't
> have an IP, nor MAC or anything that could identify it on the network.

Now I am confused.  How are you forwarding these pings as you say, Mick?
-- 
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Re: [gentoo-user] [OT] Pinging two devices on the same IP address

[Mark Shields]

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On 10/23/07, Dan Farrell <dan@spore.ath.cx> wrote:
>
> On Tue, 23 Oct 2007 18:27:10 -0300
> "Daniel da Veiga" <danieldaveiga@gmail.com> wrote:
>
> > I really don't get how you forward something to an Access Point, isn't
> > this device like a "dumb hub" on your wireless network? Mine doesn't
> > have an IP, nor MAC or anything that could identify it on the network.
>
> Now I am confused.  How are you forwarding these pings as you say, Mick?
> --
> gentoo-user@gentoo.org mailing list
>
>
Forwarding echo request/response packets (ICMP), maybe?

-- 
- Mark Shields

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Re: [gentoo-user] [OT] Pinging two devices on the same IP address

[Dan Farrell]

On Tue, 23 Oct 2007 18:12:07 -0400
"Mark Shields" <laebshade@gmail.com> wrote:

> Forwarding echo request/response packets (ICMP), maybe?

Yeah, that's what I thought, too.  But wouldn't that require an IP?  Or
at least -- at the very least -- a MAC address for Ethernet-layer
transmission of some kind?  
-- 
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Re: [gentoo-user] [OT] Pinging two devices on the same IP address

[Mick]

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On Tuesday 23 October 2007, Dan Farrell wrote:
> On Tue, 23 Oct 2007 18:12:07 -0400
>
> "Mark Shields" <laebshade@gmail.com> wrote:
> > Forwarding echo request/response packets (ICMP), maybe?
>
> Yeah, that's what I thought, too.  But wouldn't that require an IP?  Or
> at least -- at the very least -- a MAC address for Ethernet-layer
> transmission of some kind?

Thanks guys.  The AP has a reserved static LAN IP address on the router 
(10.10.10.13).  It also has a MAC.  So it is simply a matter of forwarding 
(all) ICMP echo-reply packets that arrive from the Internet to that LAN 
address. (On this implementation the AP is itself a Linksys wireless router).

I wonder if I can play tricks with ping's ICMP headers to differentiate 
between them as they come into the router, or something clever that I haven't 
yet figured out.  Any ideas?
-- 
Regards,
Mick

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Re: [gentoo-user] [OT] Pinging two devices on the same IP address

[Etaoin Shrdlu]

On Wednesday 24 October 2007, Mick wrote:

> Thanks guys.  The AP has a reserved static LAN IP address on the
> router (10.10.10.13).  It also has a MAC.  So it is simply a matter of
> forwarding (all) ICMP echo-reply packets that arrive from the Internet
> to that LAN address. (On this implementation the AP is itself a
> Linksys wireless router).
>
> I wonder if I can play tricks with ping's ICMP headers to
> differentiate between them as they come into the router, or something
> clever that I haven't yet figured out.  Any ideas?

Disclaimer: I have not tested what follows.

Can't you just use traceroute?  
If you run tracert from windows, it should already work, since it uses 
ICMP echo requests. Otherwise, you should open UDP port 33434 on the 
router.
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Re: [gentoo-user] [OT] Pinging two devices on the same IP address

[Mick]

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On Wednesday 24 October 2007, Etaoin Shrdlu wrote:
> On Wednesday 24 October 2007, Mick wrote:
> > Thanks guys.  The AP has a reserved static LAN IP address on the
> > router (10.10.10.13).  It also has a MAC.  So it is simply a matter of
> > forwarding (all) ICMP echo-reply packets that arrive from the Internet
> > to that LAN address. (On this implementation the AP is itself a
> > Linksys wireless router).
> >
> > I wonder if I can play tricks with ping's ICMP headers to
> > differentiate between them as they come into the router, or something
> > clever that I haven't yet figured out.  Any ideas?
>
> Disclaimer: I have not tested what follows.
>
> Can't you just use traceroute?
> If you run tracert from windows, it should already work, since it uses
> ICMP echo requests. Otherwise, you should open UDP port 33434 on the
> router.

I don't have access to a MS Windows machine right now, but using mtr I get:
====================================================
 [snip . . .]

 23. XX-XX-XXX-XX.dhcp.kgpt.tn.cha  6.7%    15  145.5 145.4 143.2 146.9   1.3
 24. ???                          100.0    15    0.0   0.0   0.0   0.0   0.0
 25. XX.XX.XXX.XXX                 6.7%    15  155.9 156.2 154.2 159.1   1.3
====================================================

It seems that hop 23 is the dhcp server of the ISP. Hop 25. is the public IP 
address of the router.  I assume that hop 24. is the cable modem which acts 
as a bridge(?).

Since the AP is within the LAN and the connection to it is NAT'ed, it is not 
shown above.  Am I correct in my thinking?
-- 
Regards,
Mick

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Re: [gentoo-user] [OT] Pinging two devices on the same IP address

[Etaoin Shrdlu]

On Wednesday 24 October 2007, Mick wrote:

> I don't have access to a MS Windows machine right now, but using mtr I
> get: ====================================================
>  [snip . . .]
>
>  23. XX-XX-XXX-XX.dhcp.kgpt.tn.cha  6.7%    15  145.5 145.4 143.2
> 146.9   1.3 
> 24. ???                          100.0    15    0.0   0.0  
>  0.0   0.0   0.0 
>  25. XX.XX.XXX.XXX                 6.7%    15  155.9 
> 156.2 154.2 159.1   1.3
> ====================================================
>
> It seems that hop 23 is the dhcp server of the ISP. Hop 25. is the
> public IP address of the router.  I assume that hop 24. is the cable
> modem which acts as a bridge(?).
>
> Since the AP is within the LAN and the connection to it is NAT'ed, it
> is not shown above.  Am I correct in my thinking?

From what I can see, and considering that I don't know how much 
traceroute-like mtr is and I don't know your setup, you should be 
correct. The idea is that traceroute should reach the AP if everything 
is working, it should stop at the router if the AP is not working, and 
at the hop before if the router is not working.
--
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Re: [gentoo-user] [OT] Pinging two devices on the same IP address

[Stroller]

On 23 Oct 2007, at 22:27, Daniel da Veiga wrote:
> ...
> I really don't get how you forward something to an Access Point, isn't
> this device like a "dumb hub" on your wireless network? Mine doesn't
> have an IP, nor MAC or anything that could identify it on the network.

You're making assumptions that all APs are like your own.

Your AP would appear to be operating as a transparent network bridge,  
but others operate as NAT routers. And a device operating as a "dumb"  
bridge can still have MAC & IP addresses assigned to it, should the  
manufacturer wish. I'm actually a little surprised to hear that yours  
doesn't - how does one change the SSID & wireless encryption key, if  
the AP has no IP address to connect to?

Stroller.
-- 
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Re: [gentoo-user] [OT] Pinging two devices on the same IP address

[Ricardo Saffi Marques]

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On 10/24/07, Stroller <stroller@stellar.eclipse.co.uk> wrote:
>
>
> I'm actually a little surprised to hear that yours
> doesn't - how does one change the SSID & wireless encryption key, if
> the AP has no IP address to connect to?
>
> Stroller.
>

Here at one of the University labs there is a REALLY old 802.11b 3COM AP
that is only configurable by a (lousy) software running on Windows. It's
really simple.
It's so hard dealing with it, 'cause it doesn't even have a power slot. It
uses PoE, so the only connector is the Ethernet one. :-/

Regards,

Saffi

-- 
*Ricardo Saffi Marques*
Laboratório de Administração e Segurança de Sistemas (LAS/IC)
Universidade Estadual de Campinas (UNICAMP)
*Cell:* +55 (19) 8128-0435
*Skype:* ricardo_saffi_marques
*Website:* *http://www.rsaffi.com*

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Re: [gentoo-user] [OT] Pinging two devices on the same IP address

[Daniel da Veiga]

On 10/24/07, Stroller <stroller@stellar.eclipse.co.uk> wrote:
>
> On 23 Oct 2007, at 22:27, Daniel da Veiga wrote:
> > ...
> > I really don't get how you forward something to an Access Point, isn't
> > this device like a "dumb hub" on your wireless network? Mine doesn't
> > have an IP, nor MAC or anything that could identify it on the network.
>
> You're making assumptions that all APs are like your own.
>
> Your AP would appear to be operating as a transparent network bridge,
> but others operate as NAT routers. And a device operating as a "dumb"
> bridge can still have MAC & IP addresses assigned to it, should the
> manufacturer wish. I'm actually a little surprised to hear that yours
> doesn't - how does one change the SSID & wireless encryption key, if
> the AP has no IP address to connect to?
>

Simple home APs act just like that, no address for configs or
anything, just a bridge to another network. These devices have no
config at all, they simply create an SSID with no encryption to a
wired network.

What he got is a WIRELESS ROUTER that acts like an Access Point,
providing a gateway and forwarding, linked to another router. I could
have guessed, but there was no info about that in his first post, so I
just guessed it was a simple Access Point.

-- 
Daniel da Veiga

Filosofia de TI: Programadores de verdade consideram o conceito "o que
você vê é o que você tem" tão ruim em editores de texto quanto em
mulheres. Não, o programador de verdade quer um editor de texto do
estilo "você pediu, você levou" - complicado, indecifrável, poderoso,
impiedoso, perigoso.
--
gentoo-user@gentoo.org mailing list

Re: [gentoo-user] [OT] Pinging two devices on the same IP address

[Stroller]

On 24 Oct 2007, at 15:41, Daniel da Veiga wrote:
> ...
> Simple home APs act just like that, no address for configs or
> anything, just a bridge to another network. These devices have no
> config at all, they simply create an SSID with no encryption to a
> wired network.
>
> What he got is a WIRELESS ROUTER that acts like an Access Point,
> providing a gateway and forwarding, linked to another router...

Where do you find this particular definition of an "access point"?
I would have believed the expression "wireless access point" to  
include either class of device within its definition.

I should add that there are some APish devices which bridge - i.e.  
they do not route or NAT - yet still have a MAC address & IP for  
administrative purposes.

Stroller.
-- 
gentoo-user@gentoo.org mailing list

Re: [gentoo-user] [OT] Pinging two devices on the same IP address

[Dan Farrell]

On Wed, 24 Oct 2007 19:28:16 +0100
Stroller <stroller@stellar.eclipse.co.uk> wrote:

> 
> On 24 Oct 2007, at 15:41, Daniel da Veiga wrote:
> > ...
> > Simple home APs act just like that, no address for configs or
> > anything, just a bridge to another network. These devices have no
> > config at all, they simply create an SSID with no encryption to a
> > wired network.

I had a belkin AP that I think was like this.  The windows-only control
program (wasn't running wine at the time) was a big reason I will
probaby never buy one again.  Once you build a real router, you never
go back...

> > What he got is a WIRELESS ROUTER that acts like an Access Point,
> > providing a gateway and forwarding, linked to another router...
> 
> Where do you find this particular definition of an "access point"?
> I would have believed the expression "wireless access point" to  
> include either class of device within its definition.

I agree.  I think 'AP' has come to mean, perhaps a trifle informally,
simply a device to allow wireless access to a wired network.  

> I should add that there are some APish devices which bridge - i.e.  
> they do not route or NAT - yet still have a MAC address & IP for  
> administrative purposes.
> 
> Stroller.
-- 
gentoo-user@gentoo.org mailing list

Re: [gentoo-user] [OT] Pinging two devices on the same IP address

[Daniel da Veiga]

On 10/24/07, Dan Farrell <dan@spore.ath.cx> wrote:
> On Wed, 24 Oct 2007 19:28:16 +0100
> Stroller <stroller@stellar.eclipse.co.uk> wrote:
>
> >
> > On 24 Oct 2007, at 15:41, Daniel da Veiga wrote:
> > > ...
> > > Simple home APs act just like that, no address for configs or
> > > anything, just a bridge to another network. These devices have no
> > > config at all, they simply create an SSID with no encryption to a
> > > wired network.
>
> I had a belkin AP that I think was like this.  The windows-only control
> program (wasn't running wine at the time) was a big reason I will
> probaby never buy one again.  Once you build a real router, you never
> go back...
>
> > > What he got is a WIRELESS ROUTER that acts like an Access Point,
> > > providing a gateway and forwarding, linked to another router...
> >
> > Where do you find this particular definition of an "access point"?
> > I would have believed the expression "wireless access point" to
> > include either class of device within its definition.
>
> I agree.  I think 'AP' has come to mean, perhaps a trifle informally,
> simply a device to allow wireless access to a wired network.
>

Exactly, at least where I live, if I go shopping for wireless devices,
APs are mostly this, and wireless routers are APs with routing and
forwarding. Its not like I was trying to define it, its simply how its
referred in some online stores, and thus I assumed that was the case
for the OP. Obviously I was wrong. No point in arguing that.

-- 
Daniel da Veiga

Filosofia de TI: Programadores de verdade consideram o conceito "o que
você vê é o que você tem" tão ruim em editores de texto quanto em
mulheres. Não, o programador de verdade quer um editor de texto do
estilo "você pediu, você levou" - complicado, indecifrável, poderoso,
impiedoso, perigoso.
--
gentoo-user@gentoo.org mailing list

Re: [gentoo-user] [OT] Pinging two devices on the same IP address

[Dan Farrell]

On Wed, 24 Oct 2007 22:03:22 -0300
"Daniel da Veiga" <danieldaveiga@gmail.com> wrote:

> Obviously I was wrong. No point in arguing that.

Meh, I don't see why we should all be held to formalized terms for
everything.  Understanding each other is the important thing, in my
mind.  
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