I have a CentOS VM in VirtualBox. It's configured to use 2 NICs. The first NIC is NAT and gets the DHCP from VirtualBox. It's enp0s3 and here is the configuration file:
TYPE="Ethernet"
PROXY_METHOD="none"
BROWSER_ONLY="no"
BOOTPROTO="dhcp"
DEFROUTE="yes"
IPV4_FAILURE_FATAL="no"
IPV6INIT="yes"
IPV6_AUTOCONF="yes"
IPV6_DEFROUTE="yes"
IPV6_FAILURE_FATAL="no"
IPV6_ADDR_GEN_MODE="stable-privacy"
NAME="enp0s3"
UUID="58624aa8-5032-4fa6-8f81-81f5b25dc540"
DEVICE="enp0s3"
ONBOOT="yes"
The second NIC I've specified to use a static address and it runs NAT Network in VirtualBox with an address range of 10.242.34.0/24. I toggle this interface being up or down with ifup enp0s8 or ifdown enp0s8 -- it isn't needed to be up all the time. Here's the configuration file:
TYPE=Ethernet
PROXY_METHOD=none
BROWSER_ONLY=no
BOOTPROTO=static
DEFROUTE=yes
IPV4_FAILURE_FATAL=no
IPV6INIT=yes
IPV6_AUTOCONF=yes
IPV6_DEFROUTE=yes
IPV6_FAILURE_FATAL=no
IPV6_ADDR_GEN_MODE=stable-privacy
NAME=enp0s8
UUID=fefdb96a-13f5-46c2-82d1-5a623770deac
DEVICE=enp0s8
ONBOOT=no
IPADDR=10.242.34.100
NETMASK=255.255.255.0
NM_CONTROLLED=no
IPV6_PRIVACY=no
Anyway, the problem I'm having is when I ifup enp0s8, I can see all the hosts on the 10.242.34 network but I cannot connect to the internet. I have to ifdown enp0s8 to connect to the internet -- presumably though enp0s3's NAT connection to the host computer.
If both enp0s3 and enp0s8 are both up, why cannot I get the to the internet? It's like enp0s8 blocks any other connection.