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

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
.

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