Michael Gale wrote:
Hey,
Why can you not use DNAT ?
We are not allowed to "hide" servers in a private network behind a firewall. All
servers have to have public IP numbers.
eth0:199.202.112.127/28 | eth1:199.202.112.127/29 199.202.112.132
------------ ----------
{Internet}----------->| Firewall |--------------------------->| server |
------------ ----------
Let's say I've been allocated 199.202.112.127/28 (these are made up addresses)
by my ISP, and I'm told to netmask as 255.255.255.0. Let's say I assign my
firewall the IP address of 199.202.112.130 with a netmask of 255.255.255.0 as
required. My /etc/sysconfig/network-scripts/ifcfg-eth0 will look something like
this:
DEVICE=eth0
BOOTPROTO=static
BROADCAST=199.202.112.255
HWADDR=00:10:20:30:40:50
IPADDR=199.202.112.130
NETMASK=255.255.255.0
ONBOOT=yes
TYPE=Ethernet
GATEWAY=199.202.112.1
I can then subnet eth1 as, let's say 199.202.112.127/29, but I cannot create a
private network, so /etc/sysconfig/network-scripts/ifcfg-eth1 would have to look
something like this:
DEVICE=eth1
BOOTPROTO=static
BROADCAST=199.202.112.134
HWADDR=00:10:20:30:40:50
IPADDR=199.202.112.127
NETMASK=255.255.255.248
ONBOOT=yes
TYPE=Ethernet
The problem I'm having is the netmask for the outside NIC (eth0) overlaps the
netmask for the DMZ side NIC (eth1). If I try to ping a server connected via hub
to eth1 on the firewall FROM the firewall:
# ping 199.202.112.132
Destination host unreachable
but
# ping -I eth1 199.202.112.132
works. I need to have all of the servers on the DMZ pingable from the Internet,
but still protected by a firewall.
I believe I have iptables set up to adequately protect the DMZ, but I have not
been able to solve the problem outlined above.
If you can not NAT the traffic then it needs to function as a router or
a bridge. A lot of companies use a "Interconnect". the ISP will provide
a small public subnet which is available behind a public IP.
So our ISP provides us with a /27 subnet of public IP's available behind
a public IP:
ISP -> route (X.X.X.X/27) -> external IP (Cisco router) Internal
IP[X.X.X.X/27]
So on the "internal" side of our Cisco router is a small /27 public
routeable network. We then assign the public IP's to our firewall and
other systems if needed.
You could do the same, if you were provided a small subnet. You could
also create bridge.
Michael
Sorry Michael about the off list post.
