Instaliral sum Red Hat 7.2 s 2 LAN karti (rtl8139).
    Purvata eth0 e chast ot edin mrejovi segment. Vtorata
eth1
e gateway na vtori (otdelen) mrejovi segment.
   Napravil sum suotvetnite nastroiki v
 /etc/sysconfig/network i /etc/sysctl.conf , kakto i route
table predpolagam che sum q napravil kato horata.
   eth0 e s ip: 192.168.1.10 netmask 255.255.255.224 i
default gateway 192.168.1.1 
  eth1 e s ip: 192.168.100.1 netmask 255.255.255.0
   Ot komputar s ip: 192.168.100.2 moga da ping-vam
  192.168.1.10 no nishto drugo ot tazi mreja. A ot komputera
s
 ip: 192.168.1.1 ne vijdam voub6te 192.168.100.1 da ne
govorim za ostanalite.
   Kajete kak moga da resha problema i dali e nujno da
nastroivam oshte neshto po route table.
  Predvaritelno blagodarq.

 Ами от написаното не става много ясно къде кво си правил,
ама routing-a определено трябва пак да го погледнеш.

Успех

 Pyrwo trqbwa da prowerish dali imash 1 w
/proc/sys/net/ipv4/ip_forward  !!!
 Naprawi ping ot klientska mashina w 172.168.1.x pyrwo kym
192.168.1.10. Posle i kym 192.168.100.1
 Mashinite w 192.168.1.x trqbwa da imat oswen default gw
 192.168.1.1 i statichen marshrut do 192.168.100.x prez
192.168.1.10.
 Izpolzwaj traceroute do drugata podmreva, za da widish kakwo
stawa.
 Za mashinite pyk w 192.168.100.x e dostatychno da znaqt kato
 dwfault gw 192.168.100.1 (oswen ako ne swyrzani i s drugi
mrevi).
Dano da pomogne
:-)

pravish si nqkakvo failche -> rc.local da rechem 
vav nego: 

ipchains -F
echo 1 > /proc/sys/net/ipv4/ip_forward
ifconfig eth0 inet xxx.xxx.xxx.xxx netmask xxx.xxx.xxx.xxx 
route add default gw xxx.xxx.xxx.xxx
ifconfig eth1 inet xxx.xxx.xxx.xxx netmask 255.255.255.xxx
ipchains -A forward -s xxx.xxx.xxx.xxx/24 -d 0/0 -j MASQ
tova shte ti reshi problema  ;-)