serial_to_ethernet

Serial<->Ethernet convertor

Serial<->Ethernet convertor

OS: CentOS 6.5
Hardware: PC Engines APU

This proof of concept is a serial-to-ethernet converter. It uses one IP-address per serial port, not an IP port.

IP address	IP Port	serial connection
192.168.100.101	22	ntp2 server
192.168.100.102	22	kvm host
192.168.100.103	22	nas

Configure virtual IP addresses

Create /etc/sysconfig/network-scripts/ifcfg-eth0:0

DEVICE="eth0:0"
BOOTPROTO="none"
ONBOOT="yes"
IPADDR="192.168.100.101"
NETMASK="255.255.255.0"

Create /etc/sysconfig/network-scripts/ifcfg-eth0:1

DEVICE="eth0:0"
BOOTPROTO="none"
ONBOOT="yes"
IPADDR="192.168.100.102"
NETMASK="255.255.255.0"

Create /etc/sysconfig/network-scripts/ifcfg-eth0:2

DEVICE="eth0:0"
BOOTPROTO="none"
ONBOOT="yes"
IPADDR="192.168.100.103"
NETMASK="255.255.255.0"

Restart networking
```
service network restart
```

Install and configure dropbear

Install dropbear from EPEL repository:
```
yum install dropbear
```
Make sure dropbear does not start automaticly
```
chkconfig dropbear off
```

Generate host keys.

/usr/bin/dropbearkey -t rsa -f /etc/dropbear/dropbear_rsa_host_key
/usr/bin/dropbearkey -t dss -f /etc/dropbear/dropbear_dss_host_key
/usr/bin/dropbearkey -t ecdsa -f /etc/dropbear/dropbear_ecdsa_host_key

Configure default OpenSSH daemon to listen only on management port. Edit /etc/ssh/sshd_config
```
ListenAddress 192.168.100.99
```
Restart OpenSSH service.
```
service sshd restart
```

Install and configure minicom

Install minicom:
```
yum install minicom
```

Create NTP2 server config. /etc/minirc.ntp2

pu port             /dev/ttyUSB0
pu minit
pu mreset
pu mhangup

KVM server config. Create /etc/minirc.kvm

pu port             /dev/ttyUSB1
pu minit
pu mreset
pu mhangup

NAS config. Create /etc/minirc.nas

pu port             /dev/ttyUSB2
pu minit
pu mreset
pu mhangup

Create login script

Create /usr/local/bin/serial.sh

#!/bin/bash
#disable ctrl-c ctrl-z
trap '' 2 20

connectto=`echo $SSH_CONNECTION | cut -d " " -f3`

case $connectto in
  192.168.42.27)
	/usr/bin/minicom ntp2
	;;
  192.168.42.28)
	echo "naar 28"
	;;
  *)
	echo "Connection problem to $connectto"
	exit 1
	;;
esac

Make it executable
```
chmod +x /usr/local/bin/serial.sh
```
Add the script to /etc/shells.

Create user

Add user serial:

useradd -G dialout -s /usr/local/bin/serial.sh serial

Enter password:
```
passwd serial
```

Start SSH services

You can also start a separate dropbear process per IP address.

Start dropbear SSHd services.

/usr/sbin/dropbear -g -p 192.168.100.101:22 -p 192.168.100.102:22 -p 192.168.100.103:22

Table of Contents