Very Computer

by **RicK_Murph** » Thu, 25 Sep 2008 19:26:12

I have 4 pc

pc1 10.10.10.100
pc2 10.10.1.101
pc3 10.10.1.102
pc4 10.10.1.103

pc2 have this routing table:
10.10.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
10.10.10.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
0.0.0.0 10.10.10.1 0.0.0.0 UG 0 0 0 eth1

it'is a router between 10.10.1.0/24 and 10.10.10.0/24
i do in pc2: sysctl -w net.ipv4.ip_forward=1

when i ping from pc1 to pc3 it works fine

but if i do from pc1 to 10.10.1.0/24
nmap -sS -A 10.10.1.0/24

it find only pc2 (router) because it have eth1 in the same network of pc1

in the same time if i do from pc2:
tcpdump -n -i eth0
it don't capture nothing

but
tcpdump -n -i eth1
capture the traffic

why this behavior?

thanks a lot and scuse me for my bad english

--
Riccardo (http://termitano.myminicity.com, visitate e se volete partecipate
sul http://www.iltermitano.it/)

A computer is like an air conditioner,
it stops working when you open Windows.
Registered Linux user #457776

by **Chris Davie** » Thu, 25 Sep 2008 21:11:22

> I have 4 pc
> pc1 10.10.10.100
> pc2 10.10.1.101

What's pc2's other IP address (on the 10.10.10.0/24 network)?

Quote:> pc3 10.10.1.102
> pc4 10.10.1.103
> pc2 have this routing table:
> 10.10.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
> 10.10.10.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
> 0.0.0.0 10.10.10.1 0.0.0.0 UG 0 0 0 eth1
> it'is a router between 10.10.1.0/24 and 10.10.10.0/24
> i do in pc2: sysctl -w net.ipv4.ip_forward=1
> when i ping from pc1 to pc3 it works fine
> but if i do from pc1 to 10.10.1.0/24
> nmap -sS -A 10.10.1.0/24
> it find only pc2 (router) because it have eth1 in the same network of pc1

What are the routing tables on pc1, pc3, and pc4? It looks like you may
have forgotten routes to pc2 for the "other" network.

Chris

by **RicK_Murph** » Thu, 25 Sep 2008 22:15:24

> RicK_Murphy

>

>> I have 4 pc

>> pc1 10.10.10.100
>> pc2 10.10.1.101

> What's pc2's other IP address (on the 10.10.10.0/24 network)?

eth1 of pc2: 10.10.10.101

Quote:>> pc3 10.10.1.102
>> pc4 10.10.1.103

>> pc2 have this routing table:
>> 10.10.1.0 0.0.0.0 255.255.255.0 U 0 0 0
>> eth0
>> 10.10.10.0 0.0.0.0 255.255.255.0 U 0 0 0
>> eth1
>> 0.0.0.0 10.10.10.1 0.0.0.0 UG 0 0 0
>> eth1

>> it'is a router between 10.10.1.0/24 and 10.10.10.0/24
>> i do in pc2: sysctl -w net.ipv4.ip_forward=1

>> when i ping from pc1 to pc3 it works fine

>> but if i do from pc1 to 10.10.1.0/24
>> nmap -sS -A 10.10.1.0/24

>> it find only pc2 (router) because it have eth1 in the same network of pc1

> What are the routing tables on pc1, pc3, and pc4? It looks like you may
> have forgotten routes to pc2 for the "other" network.

in pc1:
10.10.1.0 10.10.10.101 255.255.255.0 UG 0 0 0 eth1
10.0.0.0 0.0.0.0 255.0.0.0 U 0 0 0 eth1
0.0.0.0 10.10.10.1 0.0.0.0 UG 0 0 0 eth1

in pc3, pc4:
10.10.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
0.0.0.0 10.10.1.101 0.0.0.0 UG 0 0 0 eth0

observe that ping works fine

Quote:
> Chris

thanks
--
Riccardo (http://termitano.myminicity.com, visitate e se volete partecipate
sul http://www.iltermitano.it/)

A computer is like an air conditioner,
it stops working when you open Windows.
Registered Linux user #457776

by **Ravenp** » Thu, 25 Sep 2008 22:53:37

Hi. I find that, sometimes, ping lies. Are you, for example, able to
actually ssh from pc1 to pc3? I'm guessing no. That being said, I'd
be interested in knowing what the routing tables on pc2, and pc3 are;
do you have 10.10.1.101 as their default gateway? And how about pc1?
You don't state what the IP address for eth1 on pc2 is, but that had
better be the default gateway on pc1 or else things won't work right.
So, to summarize:
1) What are your routing tables on pc1, pc3 and pc4?
2) What is eth1's IP address on pc2?

-Ken

On Sep 24, 6:26?am, RicK_Murphy
>

Quote:> I have 4 pc

> pc1 10.10.10.100
> pc2 10.10.1.101
> pc3 10.10.1.102
> pc4 10.10.1.103

> pc2 have this routing table:
> 10.10.1.0 ? ? ? 0.0.0.0 ? ? ? ? 255.255.255.0 ? U ? ? 0 ? ? ?0 ? ? ? ?0 eth0
> 10.10.10.0 ? ? ?0.0.0.0 ? ? ? ? 255.255.255.0 ? U ? ? 0 ? ? ?0 ? ? ? ?0 eth1
> 0.0.0.0 ? ? ? ? 10.10.10.1 ? ? ?0.0.0.0 ? ? ? ? UG ? ?0 ? ? ?0 ? ? ? ?0 eth1

> it'is a router between 10.10.1.0/24 and 10.10.10.0/24
> i do in pc2: sysctl -w net.ipv4.ip_forward=1

> when i ping from pc1 to pc3 it works fine

> but if i do from pc1 to 10.10.1.0/24
> ?nmap -sS -A 10.10.1.0/24

> it find only pc2 (router) because it have eth1 in the same network of pc1

> in the same time if i do from pc2:
> tcpdump -n -i eth0
> it don't capture nothing

> but
> tcpdump -n -i eth1
> capture the traffic

> why this behavior?

> thanks a lot and scuse me for my bad english

> --
> Riccardo (http://termitano.myminicity.com, visitate e se volete partecipate
> sulhttp://www.iltermitano.it/)

> A computer is like an air conditioner,
> it stops working when you open Windows.
> Registered Linux user #457776

by **RicK_Murph** » Thu, 25 Sep 2008 23:05:43

> Hi. I find that, sometimes, ping lies. Are you, for example, able to
> actually ssh from pc1 to pc3? I'm guessing no.

I tryed

it's work fine

Quote:> 1) What are your routing tables on pc1, pc3 and pc4?

in pc1:
10.10.1.0 ? ? ? 10.10.10.101 ? ?255.255.255.0 ? UG ? ?0 ? ? ?0 ? ? ? ?0 eth1
10.0.0.0 ? ? ? ?0.0.0.0 ? ? ? ? 255.0.0.0 ? ? ? U ? ? 0 ? ? ?0 ? ? ? ?0 eth1
0.0.0.0 ? ? ? ? 10.10.10.1 ? ? ?0.0.0.0 ? ? ? ? UG ? ?0 ? ? ?0 ? ? ? ?0 eth1

in pc3, pc4:
10.10.1.0 ? ? ? 0.0.0.0 ? ? ? ? 255.255.255.0 ? U ? ? 0 ? ? ?0 ? ? ? ?0 eth0
0.0.0.0 ? ? ? ? 10.10.1.101 ? ? 0.0.0.0 ? ? ? ? UG ? ?0 ? ? ?0 ? ? ? ?0 eth0

Quote:> 2) What is eth1's IP address on pc2?

10.10.10.101

--
Riccardo (http://termitano.myminicity.com, visitate e se volete partecipate
sul http://www.iltermitano.it/)

A computer is like an air conditioner,
it stops working when you open Windows.
Registered Linux user #457776

Very Computer

nmap from net a to net B, don't work, but ping yes

nmap from net a to net B, don't work, but ping yes

nmap from net a to net B, don't work, but ping yes

nmap from net a to net B, don't work, but ping yes

nmap from net a to net B, don't work, but ping yes

nmap from net a to net B, don't work, but ping yes