Help please, i'm totally confused. The problem is that i get gateway unreachable message from route command

I have a Mandrake 9.0-router with 2 NICs:
eth0 - 192.168.0.1 - Local NET (192.168.0.0/24)
eth1 - X.Y.Z.66 - external NET (X.Y.Z.64/28)
It connect to a CISCO-gateway with IP X.Y.Z.65

route -n:
Dest Gateway NetMask Flags Iface
X.Y.Z.64 0.0.0.0 255.255.255.240 U eth1
192.168.0.0 0.0.0.0 255.255.255.0 U eth0
127.0.0.0 0.0.0.0 255.0.0.0 U lo
0.0.0.0 X.Y.Z.65 0.0.0.0 UG eth1

route:
Dest Gateway NetMask Flags Iface
outer * 255.255.255.240 U eth1
inner * 255.255.255.0 U eth0
127.0.0.0 * 255.0.0.0 U lo
default unreachable 0.0.0.0 UG eth1

All 127.0.0.1, 192.168.0.1, X.Y.Z.66, X.Y.Z.65 Ping OK (for example .65): [root@si stat]# ping X.Y.Z.65
PING X.Y.Z.65 (X.Y.Z.65) from X.Y.Z.66 : 56(84) bytes of data.
64 bytes from X.Y.Z.65: icmp_seq=1 ttl=255 time=0.553 ms
64 bytes from X.Y.Z.65: icmp_seq=2 ttl=255 time=0.487 ms
64 bytes from X.Y.Z.65: icmp_seq=3 ttl=255 time=0.499 ms

--- X.Y.Z.65 ping statistics ---
3 packets transmitted, 3 received, 0% loss, time 1998ms
rtt min/avg/max/mdev = 0.487/0.513/0.553/0.028 ms

Local NET is masqueraded by 217.76.40.66 (iptables) and INTERNET access is OK. But why gateway unreachable ??? May be something wrong with NAT setting ?? Help please. I give any additional information about any configs or hardware

Have you tried adding the default?

route add default gw X.Y.Z.65

NOTE if you have a line in /etc/hosts
X.Y.Z.65 router
then you could use router in the above command instead of the IP.

Yes of course, default gateway added or there would be no access to the Internet.