[gentoo-user] [OT] network discovery tools

[gentoo-user] [OT] network discovery tools

[Harry Putnam]

There must be a number of people who post here that have had to do
this problem.

Discover the addresses of computers on a home network that have
connected by way of DHCP.  For example: Several wireless connections.

I've used static IPS for around 10 yrs, always seemed handier for
things like ssh between home lan computers. 

But recently started using DHCP for wireless connections.  It must be
such a popular method for some reason.

But when you do it that way, and say want to VNC or ssh or the like to
something connected by a dhcp serving WAP then how do you find the
address?

That is, besides something like accessing the WAP and checking the IPs
connected to it.

Is there some quick and sure way to discover any IPs on the home lan?

Some kind of mapper tool?

Re: [gentoo-user] [OT] network discovery tools

[Stéphane Guedon]

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On Wednesday 25 May 2011 21:45:07 Harry Putnam wrote:
> There must be a number of people who post here that have had to do
> this problem.
> 
> Discover the addresses of computers on a home network that have
> connected by way of DHCP.  For example: Several wireless connections.
> 
> I've used static IPS for around 10 yrs, always seemed handier for
> things like ssh between home lan computers.
> 
> But recently started using DHCP for wireless connections.  It must be
> such a popular method for some reason.
> 
> But when you do it that way, and say want to VNC or ssh or the like to
> something connected by a dhcp serving WAP then how do you find the
> address?
> 
> That is, besides something like accessing the WAP and checking the IPs
> connected to it.
> 
> Is there some quick and sure way to discover any IPs on the home lan?
> 
> Some kind of mapper tool?

dhcp can assign static adresses ! Thus, it's easier to manage (only the dhcp 
server to admin !)

I am not english, thus, don't know website with such doc (in english) but you 
can easily find it on internet !

You have also dnsmasq that makes both dns (for lan) + dhcp (whereas commonly, 
this functions are split)
-- 
Stéphane Guedon
page web : http://www.22decembre.eu/
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Re: [gentoo-user] [OT] network discovery tools

[Vincent-Xavier JUMEL]

Le 25 mai à 21:54 Stéphane Guedon a écrit
> On Wednesday 25 May 2011 21:45:07 Harry Putnam wrote:
> > There must be a number of people who post here that have had to do
> > this problem.
> > 
> > Discover the addresses of computers on a home network that have
> > connected by way of DHCP.  For example: Several wireless connections.
> > 

« ip a s » to get your IP with your mask and then « nmap
ip.in.v4.format/mask »

> > I've used static IPS for around 10 yrs, always seemed handier for
> > things like ssh between home lan computers.
> > 
> > But recently started using DHCP for wireless connections.  It must
> > be such a popular method for some reason.
> > 
> > But when you do it that way, and say want to VNC or ssh or the like
> > to something connected by a dhcp serving WAP then how do you find
> > the address?
> > 
avahi and zeroconf could be an help. With avahi-daemon running every
where and avahi-dnsconfd I just type « ssh -l login myhostname.local »
or « ssh -l login myhostname.lan » depending on your configuration.

> > That is, besides something like accessing the WAP and checking the IPs
> > connected to it.
> > 
> > Is there some quick and sure way to discover any IPs on the home lan?
> >
> > Some kind of mapper tool?
You've got lanmap to, though it doesn't seem maintained IMHO and it
depends on nmap.

> 
> dhcp can assign static adresses ! Thus, it's easier to manage (only the dhcp 
> server to admin !)
> 
> I am not english, thus, don't know website with such doc (in english) but you 
> can easily find it on internet !
> 
Configuration sample are even given in isc-dhcp-server default conf
file, richly commented out.

> You have also dnsmasq that makes both dns (for lan) + dhcp (whereas commonly, 
> this functions are split)
-- 
Vincent-Xavier JUMEL GPG Id: 0x2E14CE70 http://thetys-retz.net

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[gentoo-user] Re: [OT] network discovery tools

[Grant Edwards]

On 2011-05-25, Harry Putnam <reader@newsguy.com> wrote:

> There must be a number of people who post here that have had to do
> this problem.
>
> Discover the addresses of computers on a home network that have
> connected by way of DHCP.  For example: Several wireless connections.
>
> I've used static IPs for around 10 yrs, always seemed handier for
> things like ssh between home lan computers. 
>
> But recently started using DHCP for wireless connections.  It must be
> such a popular method for some reason.
>
> But when you do it that way, and say want to VNC or ssh or the like to
> something connected by a dhcp serving WAP then how do you find the
> address?

The best thing to do is to use a DHCP server and DNS server that are
"connected" somehow.  Then hostnames "just work".  Or you can
statically assign IP addresses in the DHCP server so that DHCP clients
always get hard-wired IP addresses that match up with the /etc/hosts
file on the DNS server.

I use OpenWRT for WAP, DNS, and DHCP, and it all pretty much "just
works".  When a DHCP client is assigned an IP address, the DNS server
knows about it and you can access it by it's hostname just the way you
would with a static setup.

For various reasons, I assign static IP addresses to a number of
devices, but I do it via the DHCP server's configuration, not by
configuring each individual device.

-- 
Grant Edwards               grant.b.edwards        Yow! Did an Italian CRANE
                                  at               OPERATOR just experience
                              gmail.com            uninhibited sensations in
                                                   a MALIBU HOT TUB?

[gentoo-user] Re: [OT] network discovery tools

[Harry Putnam]

Grant Edwards <grant.b.edwards@gmail.com> writes:

[...]

>> But when you do it that way, and say want to VNC or ssh or the like to
>> something connected by a dhcp serving WAP then how do you find the
>> address?
>
> The best thing to do is to use a DHCP server and DNS server that are
> "connected" somehow.  Then hostnames "just work".  Or you can
> statically assign IP addresses in the DHCP server so that DHCP clients
> always get hard-wired IP addresses that match up with the /etc/hosts
> file on the DNS server.
>
> I use OpenWRT for WAP, DNS, and DHCP, and it all pretty much "just
> works".  When a DHCP client is assigned an IP address, the DNS server
> knows about it and you can access it by it's hostname just the way you
> would with a static setup.
>
> For various reasons, I assign static IP addresses to a number of
> devices, but I do it via the DHCP server's configuration, not by
> configuring each individual device.

That sounds like a good plan... and worth some thought.  However I was
only asking to find IPs on the home lan after the fact.  Not the
general question of how to setup the lan (though I welcome the ideas
you present).

I seem to have latched onto a tool by a bit more googling, and getting
lucky, called netdiscover that is in portage now.

Just one simple command found all machines active on the home lan
including those with DHCP served addresses:

    netdiscover -i eth0 <ENTER>

Oddly a similar command but aimed at a range misses a few:

    netdiscover -i eth0 -r 192.168.0.0/24 <ENTER>

I guess the tool may use some heuristics if you give it less info.

And for one reason or another a plain `arp' command misses several of
those discovered with `netdiscover -i eth0'

So I found what I needed... thanks.

Re: [gentoo-user] Re: [OT] network discovery tools

[Neil Bothwick]

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On Wed, 25 May 2011 15:28:04 -0500, Harry Putnam wrote:

> Just one simple command found all machines active on the home lan
> including those with DHCP served addresses:
> 
>     netdiscover -i eth0 <ENTER>

Thanks, I wasn't aware of netdiscover and it's a perfect fit for
something I needed this week.


-- 
Neil Bothwick

Set phasers to extreme itching!

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Re: [gentoo-user] [OT] network discovery tools

[Neil Bothwick]

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On Wed, 25 May 2011 14:45:07 -0500, Harry Putnam wrote:

> Is there some quick and sure way to discover any IPs on the home lan?
> 
> Some kind of mapper tool?

Do you know the MAC address of the device? That's usually written on the
box somewhere, so you can usually examine the output of arp -n to findthe
associated IP address.

If it's not in the arp table, and it's your network, a QAD method is

sudo nmap -sP 192.168.0.1-254 | grep -B 3 MACaddress

Substituting the address range of your network if it's not 192.168.0.


-- 
Neil Bothwick

WinErr 007: System price error - Inadequate money spent on hardware

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Re: [gentoo-user] [OT] network discovery tools

[Florian Philipp]

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Am 25.05.2011 21:45, schrieb Harry Putnam:
> There must be a number of people who post here that have had to do
> this problem.
> 
> Discover the addresses of computers on a home network that have
> connected by way of DHCP.  For example: Several wireless connections.
> 
> I've used static IPS for around 10 yrs, always seemed handier for
> things like ssh between home lan computers. 
> 
> But recently started using DHCP for wireless connections.  It must be
> such a popular method for some reason.
> 
> But when you do it that way, and say want to VNC or ssh or the like to
> something connected by a dhcp serving WAP then how do you find the
> address?
> 
> That is, besides something like accessing the WAP and checking the IPs
> connected to it.
> 
> Is there some quick and sure way to discover any IPs on the home lan?
> 
> Some kind of mapper tool?
> 
> 

While I personally prefer a combined DHCP+DNS server like dnsmasq, you
can also take a look at the whole Zeroconf/MDNS/Avahi/Bonjour stack.

I'm not really sure if you can configure common devices and Linux PCs to
use the DNS server for internet addresses and MDNS for local ones. In
theory, it should be possible since you can distinguish them (local
addresses should not be fully qualified _or_ have the domain .local).

net-misc/mDNSResponder, sys-auth/nss-mdns and net-dns/avahi are probably
good starting points.

Hope this helps,
Florian Philipp


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Re: [gentoo-user] [OT] network discovery tools

[Mick]

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On Thursday 26 May 2011 17:24:05 Florian Philipp wrote:
> Am 25.05.2011 21:45, schrieb Harry Putnam:
> > There must be a number of people who post here that have had to do
> > this problem.
> > 
> > Discover the addresses of computers on a home network that have
> > connected by way of DHCP.  For example: Several wireless connections.
> > 
> > I've used static IPS for around 10 yrs, always seemed handier for
> > things like ssh between home lan computers.
> > 
> > But recently started using DHCP for wireless connections.  It must be
> > such a popular method for some reason.
> > 
> > But when you do it that way, and say want to VNC or ssh or the like to
> > something connected by a dhcp serving WAP then how do you find the
> > address?
> > 
> > That is, besides something like accessing the WAP and checking the IPs
> > connected to it.
> > 
> > Is there some quick and sure way to discover any IPs on the home lan?
> > 
> > Some kind of mapper tool?
> 
> While I personally prefer a combined DHCP+DNS server like dnsmasq, you
> can also take a look at the whole Zeroconf/MDNS/Avahi/Bonjour stack.
> 
> I'm not really sure if you can configure common devices and Linux PCs to
> use the DNS server for internet addresses and MDNS for local ones. In
> theory, it should be possible since you can distinguish them (local
> addresses should not be fully qualified _or_ have the domain .local).
> 
> net-misc/mDNSResponder, sys-auth/nss-mdns and net-dns/avahi are probably
> good starting points.

netdiscover seems to do exactly what the OP asked for, although I have used 
arping and a couple of scripts I found on the net and modified them.

The first looks like this:
=============================
#!/usr/bin/env bash

quit_on_found=0
packet_count=2
subnet=""
verbose="-q"

usage()
{
cat << EOF
find_ip 1.0 Robin Wood (dninja@gmail.com) (www.digininja.org)

Find used and unused IPs on a network you don't haven an IP address on

usage: $0 options

OPTIONS:
        -h                Show this message
        -c <packet count> The number of ping packets to send, default 2
        -s <subnet>       First 3 parts of the subnet to test, default 
192.168.0
        -q                Quit when found first free address, default keep 
going
        -v                Verbose

EOF
}

have_arping=`which arping`

if [[ "$have_arping" == "" ]]
then
cat << EOF
usage: $0 options

You must have arping installed and in the current path for this scanner to 
work
EOF
        exit 1
fi

while getopts  ":hvs:qc:" flag
do
        case $flag in
                h)
                        usage
                        exit 1
                        ;;
                c)
                        packet_count=$OPTARG
                        ;;
                q)
                        quit_on_found=1
                        ;;
                s)
                        subnet=$OPTARG
                        ;;
                v)
                        verbose=""
                        ;;
                ?)
                        usage
                        exit 1
                        ;;
        esac
done

if [[ "$subnet" == "" ]]
then
cat << EOF
usage: $0 options

You must provide a subnet
EOF
        exit 1
fi

if [[ "$verbose" == "" ]]
then
        if [[ $quit_on_found == 1 ]]
        then
                echo "Quiting when found a free address"
        fi
        echo "Testing subnet $subnet.0/24"
        echo "Sending $packet_count packets per IP"
fi

for i in {1..254}
do
        IP=$subnet.$i
        arping $verbose -c $packet_count $IP
        result=$?
        if [[ $result == 0 ]]
        then
                echo "$IP Used"
        else
                echo "$IP Free"
                if [[ $quit_on_found == 1 ]]
                then
                        exit
                fi
        fi
done
=============================

Google for "find_ip.sh"

The other which I can't find at the moment prints out the MAC address of each 
IP address that is in use.  Alternatively, run the above script with the -v 
option and then scroll back to look at the MAC addresses.

Of course, I was using this before I knew that netdiscover existed - thanks 
for sharing!
-- 
Regards,
Mick

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[gentoo-user] Re: [OT] network discovery tools

[James]

Harry Putnam <reader <at> newsguy.com> writes:


> Is there some quick and sure way to discover any IPs on the home lan?

emerge fping
<man fping>

fping -g 192.168.222.0/24


searches quite fast and accurate...


hth,
James

[gentoo-user] Re: [OT] network discovery tools

[Harry Putnam]

James <wireless@tampabay.rr.com> writes:

> Harry Putnam <reader <at> newsguy.com> writes:
>
>
>> Is there some quick and sure way to discover any IPs on the home lan?
>
> emerge fping
> <man fping>
>
> fping -g 192.168.222.0/24
>
>
> searches quite fast and accurate...

Yup, that's quick and easy... thanks