DdB wrote: > What i am trying to setup is to have an older unused pc act as a > backup-server. The first thing to do would be to install a current > debian (disks are already pluged in). And the installation absolutely > wants an internet connection. > > Due to physical restrictions, my router has only one connection (used by > my main host), but there are more networking cards in it, so i am > intending to allow a connection from the host to the backuup server, > later that net is going to be used for the backing up of data. But now, > i would like to avoid any additional hardware (like bridge, router, > twisted pair, or such) and just have the backup server connect with a > normal network cable (rj-45?) to a secondary network card of the host, > and have the latter allow internet access thru it. (dhcp or fixed > address, whatever is easier)
RJ45 is a physical connector with 8 pairs of twisted wires. The twisted pairs carry the same signal but with the polarity reversed, + on one is - on the other. Together with the twisting, that makes the signal being carried resistant to interference. Ethernet is a low level protocol often carried by RJ45-connected twisted pair cables. Bridging extends a network segment. Routing makes decisions about where IP packets should go. The router that connects to the internet for you is probably doing several jobs: - it is bridging from a long-haul network like xDSL, DOCSIS (cable modem), or fiber, to your local ethernet - it is acquiring an IP address from the provider and using it as your public address - it is probably using network address translation (NAT) to allow multiple internal addresses to masquerade as the single public address - it is probably providing those internal addresses via DHCP It would be reasonably cheap to put an ethernet switch between the router and your existing host and new backup host. In the US, an 8 port ethernet switch is $28: https://www.newegg.com/netgear-gs308-300pas-8-x-rj45/p/N82E16833222029?Item=N82E16833222029 and you would need at least two more ethernet cables, which are also cheap. $7.50 for preterminated 25 foot cable https://www.newegg.com/yellow-belkin-25-ft-accessories-cable-management/p/N82E16812107315?Item=9SIB897JGS5925 I presume that there are similar companies in Germany which will sell you basically the same things. You unplug the host from the router, plug the router into the switch, and the two hosts into the switch. No configuration changes, most likely. Everything is likely to work. --- If you insist on plugging your second host directly into your first, you can do that instead: - configure an ethernet interface on both sides with an RFC1918 network address - plug them into each other - you can now ping each from the other - now you configure routing and NAT masquerading on your primary host to hide the secondary host behind it I don't recommend this. Buy a switch and some cables. -dsr-
