Here's the problem:
Provider has given to us a public IP address space x.y.z.0/28 where x.y.z.1 is address of an interface on their own network device, which should be a default gateway to our server, according to their words. There is an optical link between provider and optical converter on the side of server, and electrical link from converter to the server.
I have configured the server primary network interface this way:
ifconfig eth0 x.y.z.2/28 up
route add default gw x.y.z.1 netmask 255.255.255.240 dev eth0
But, when I try to ping x.y.z.1, icmp tells me that Destination host is unreachable iptables installed but policy is ACCEPT everywhere.
It's very interesanting that link is not showing any activity, by the LED diods on NIC. I tried other NIC, and it's the same case. I tried even on my laptop with windows OS, and I didn't get any reasonable notification, instead I got Network cable unplugged?!
But when I put the cable into the other server with Windows server 2003, NIC's LEDs show activity. That server is giving access to the internet only about 10 minutes after restarting, after it stops serving, probably NATing, for unexplained reasons to me . I don't have insight to win server, cause it's under password of other admin who is not available anymore, so it was the reason to build a debian server from scratch, but on the very beggining big problem is in front of me.
So, does anyone have an idea what is the cause of problem and how to solve it?