Re: [LARTC] how can I monitor a (dumb) switch ?

Re: [LARTC] how can I monitor a (dumb) switch ?

[cristian_dimache]

Hi, Radu

You simply cannot monitor a switch that is uncapable of monitoring.
It is as easy as that.
Nevertheless, you can fake the monitoring part by arping to the users
connected directly to that switch.
Arping, because is a layer2 app, goes beyond (or better yet, beneath) any
firewall. If a firewall blocks broadcast arp requests, then it will render
the machine network-less, so no firewall does that.

So, grab your linux box, and start arping!

P.S. Read the thread on mac and IP changing, I feel like we are in rather
the same position...

> Hello there,
>
> Can anyone help me with a problem i have....
>
> I have an ethernet LAN, made over dumb fast-ethernet switches
> (10/100mbit) without management, so there is no IP for the switches.
>
> What I want, if possible, is to find out if a switch is down or not.
>
> It's like with routers... if you want to find out if a router is OK,
> either you send ICMP directly to the router, or to a host "behind" the
> router.
>
> Is there any device, or ANY OTHER possibility that I can find out if a
> switch is unplugged or broken.  Users on my LAN aren't reliable (they
> have firewalls, closed computers, etc.), so pinging users that are
> linked to a switch to find out is out of the question.
>
> I have got an ideea that if I take an ehernet card, and somehow manage
> to put power in it, than I would have a device with MAC addres to
> arping ... is this correct ?
>
> MANY thanks in advance, and SORRY for being a bit out of topic.
>
>
> Best regards,
> Radu.
>
> --
>
>
> Radu Cugut
>
> mobile: +40 742 045686
> web:    http://rcugut.has.it
> _______________________________________________
> LARTC mailing list
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> http://mailman.ds9a.nl/cgi-bin/mailman/listinfo/lartc
>


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[LARTC] how can I monitor a (dumb) switch ?

[Radu CUGUT]

Hello there,

Can anyone help me with a problem i have....

I have an ethernet LAN, made over dumb fast-ethernet switches
(10/100mbit) without management, so there is no IP for the switches.

What I want, if possible, is to find out if a switch is down or not.

It's like with routers... if you want to find out if a router is OK,
either you send ICMP directly to the router, or to a host "behind" the
router.

Is there any device, or ANY OTHER possibility that I can find out if a
switch is unplugged or broken.  Users on my LAN aren't reliable (they
have firewalls, closed computers, etc.), so pinging users that are
linked to a switch to find out is out of the question.

I have got an ideea that if I take an ehernet card, and somehow manage
to put power in it, than I would have a device with MAC addres to
arping ... is this correct ?

MANY thanks in advance, and SORRY for being a bit out of topic.


Best regards,
Radu.

-- 


Radu Cugut

mobile: +40 742 045686
web:    http://rcugut.has.it
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Re: [LARTC] how can I monitor a (dumb) switch ?

[Daniel Lopes]

Radu CUGUT schrieb:
> Hello there,
> 
> Can anyone help me with a problem i have....
> 
> I have an ethernet LAN, made over dumb fast-ethernet switches
> (10/100mbit) without management, so there is no IP for the switches.
> 
> What I want, if possible, is to find out if a switch is down or not.
> 
> It's like with routers... if you want to find out if a router is OK,
> either you send ICMP directly to the router, or to a host "behind" the
> router.
> 
> Is there any device, or ANY OTHER possibility that I can find out if a
> switch is unplugged or broken.  Users on my LAN aren't reliable (they
> have firewalls, closed computers, etc.), so pinging users that are
> linked to a switch to find out is out of the question.
> 
> I have got an ideea that if I take an ehernet card, and somehow manage
> to put power in it, than I would have a device with MAC addres to
> arping ... is this correct ?
> 
> MANY thanks in advance, and SORRY for being a bit out of topic.
> 
> 
> Best regards,
> Radu.
> 
Ping a client you surely know should be connected to the switch. ARP 
will take the part to find out the hardware address so the packet can be 
delivered. If the switch is on it should find a hardware address and ARP 
should put it in your ARP cache. It´s independet from ICMP blocks and 
similar. So after trying to ping you should have an entry in your ARP 
table which you can control with "arp" command.

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Re: [LARTC] how can I monitor a (dumb) switch ?

[Dmytro O. Redchuk]

On Fri, Jun 03, 2005 at 11:24:13AM +0300, Radu CUGUT wrote:
> Hello there,
> 
> Can anyone help me with a problem i have....
> 
> I have an ethernet LAN, made over dumb fast-ethernet switches
> (10/100mbit) without management, so there is no IP for the switches.
> 
> What I want, if possible, is to find out if a switch is down or not.
:-)
((never tried, didnt think even a little, but...))

Plug two more cards into you linux box, connect them both to the switch,
make them an interfaces of one bridge inside you linux box and bring up
STP over there. I guess bridge should detect a loop quickly and block one
port. Then you'll be able to monitor bridge's state.

Uh?


Sorry if I'm wrong!-) It's possible quite now...

> 
> Best regards,
> Radu.
> 
> -- 

-- 
  _,-=._              /|_/|
  `-.}   `=._,.-=-._.,  @ @._,
     `._ _,-.   )      _,.-'
        `    G.m-"^m`m'        Dmytro O. Redchuk

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Re: [LARTC] how can I monitor a (dumb) switch ?

[Jay Vosburgh]

Dmytro O. Redchuk <dor@ldc.net> wrote:

>On Fri, Jun 03, 2005 at 11:24:13AM +0300, Radu CUGUT wrote:
>> I have an ethernet LAN, made over dumb fast-ethernet switches
>> (10/100mbit) without management, so there is no IP for the switches.
>> 
>> What I want, if possible, is to find out if a switch is down or not.
[...]
>Plug two more cards into you linux box, connect them both to the switch,
>make them an interfaces of one bridge inside you linux box and bring up
>STP over there. I guess bridge should detect a loop quickly and block one
>port. Then you'll be able to monitor bridge's state.

	I suspect that the bonding driver would also do what you're
looking for.  Docs can be found at:

	http://sourceforge.net/projects/bonding

	It can either monitor the link state, or issue ARP probes (as
somebody else suggested) to check connectivity to a peer on the local
network.  Judging from my experience with managed switches, I suspect
that the bonding driver (in active-backup mode, for example) would
detect link failure faster than STP.

	-J

---
	-Jay Vosburgh, IBM Linux Technology Center, fubar@us.ibm.com

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