Networking vserver guests RHEL

Public IP Space

5.5.5.5

Chose a private IP range

Private IP Range: 192.168.1.0
Host Private IP: 192.168.1.1
Guest Private IP: 192.168.1.2

network-scripts

In a RHEL based system many configurations are stored in /etc/sysconfig. The network settings are /etc/sysconfig/network-scripts.

cp /etc/sysconfig/network-scripts/ifcfg-eth0 /etc/sysconfig/network-scripts/ifcfg-eth0:1
vi  /etc/sysconfig/network-scripts/ifcfg-eth0:1

DEVICE=eth0:1
HWADDR=00:0e:0c:69:ed:e0
ONBOOT=yes
NETMASK=255.255.255.0
IPADDR=192.168.1.1
TYPE=Ethernet

This IP address will now start at boot up.

ifup eth0:1

Assuming your vserver is test01

echo "eth0:1" > /etc/vservers/test01/interfaces/0/dev
echo "192.168.1.2" > /etc/vservers/test01/interfaces/0/ip
echo "255.255.255.0" > /etc/vservers/test01/interfaces/0/mask

You can use iptables to make youre system act as a router.

iptables -t nat -A POSTROUTING -s 192.168.1.0/24 \ 
  -d ! 192.168.1.0/24 -j SNAT --to-source 5.5.5.5
iptables-save > /etc/sysconfig/iptables

Now your guest should have outbound connectivity.

[root@34 ~]# vserver test01 enter
bash-3.1# ifconfig 
eth0      Link encap:Ethernet  HWaddr 00:0E:0C:69:ED:E0  
          inet addr:10.10.10.2  Bcast:10.10.10.255  Mask:255.255.255.0
...
bash-3.1# ping www.google.com
PING www.l.google.com (74.125.45.99) 56(84) bytes of data.
64 bytes from yx-in-f99.google.com (74.125.45.99): icmp_seq=1 ttl=244 time=22.3 ms
64 bytes from yx-in-f99.google.com (74.125.45.99): icmp_seq=2 ttl=244 time=22.5 ms

Inbound Connections and NAT

Now we have to establish inbound connectivity. This can be done with Network Address Translation. We can expose the SSH service through NAT.

5.5.5.5:9000->192.168.1.2:22

iptables -t nat -A PREROUTING -s ! 192.168.1.0/24 \
  -m tcp -p tcp --dport 9000  -j DNAT --to-destination 192.168.1.2:22
iptables-save > /etc/sysconfig/iptables