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2021-01-21 | Transport | Crossover Cable

As I write this, you can get a Ryzen 5 (four cores, eight threads) with 32GB RAM and a 1TB NVMe SSD for less than $700 US, and it has a built in gigabit Ethernet as well as wireless. The simplest way to network two machines is to use a crossover cable:

Add one of these to your kit. To verify, for a crossover cable you need to connect 1 to 3, 2 to 6, 3 to 1 and 6 to 2. Look at the flat side. The numbers go from left to right.

Likely you will need to assign an IP address to each machine, as you won't have a DHCP server to issue you one. Setting a static IP address on L1G3R can be done by /etc/sysconfig/ifconfig.eth0:

ONBOOT=yes  
IFACE=enp3s0  
SERVICE=ipv4-static
IP=192.168.1.51
PREFIX=24
BROADCAST=192.168.51.255

I'm sure there is a better way to get the IFACE name, but I just look for this the eth0 line on boot using the dmesg command:

dmesg | grep eth
[    3.275379] r8169 0000:03:00.0 eth0: RTL8168h/8111h, a8:a1:59:23:65:c1, XID 541, IRQ 91
[    3.275527] r8169 0000:03:00.0 eth0: jumbo features [frames: 9200 bytes, tx checksumming: ko]
[    3.538604] r8169 0000:03:00.0 enp3s0: renamed from eth0

Use different IP addresses on the two hosts by changing the number on the far right (called the last octet).

Most people run wireless in their homes, but often the wireless router won't allow the machines to talk to each other. This can be configured as well, but is beyond the scope of this article on a crossover cable. It is counter-intuitive, but as we rely on cloud more and more, we often don't notice that machines in the same house can't talk to each other without internet connectivity via a cloud app. It might also be wise to pick up a cheap gigabit switch if you have more than two devices that need to communicate.

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