2 internet ip numbers on eth0

2 internet ip numbers on eth0

[Fonz]

Hi,

I am migrating from one ISP to another, and would like to run both
simultaneously for a while.

So:
	(both netmask 255.255.255.248)
[ISP1] 24.106.62.180	[ISP2] 209.181.237.230
		|				|
		|				|
		\				/
		 -----[    HUB	]-----
				|
				|
		 -------- eth0 ---------
		|	Linux FW/Server	|
		 ---------eth1 ---------
				|
				|
			[    HUB	]
				|
			10.0.0.x/255.255.255.0

The default IP on eth0 in my RedHat 7.2 box is ISP1 and it's default route
to ISP1's gateway.

I am getting rid of ISP2 in the future. Until then, I want to either forward
all request coming in on ISP2 to ISP1 so all ISP1 firewall rules will apply,
or just maintain separate rules for them, whichever is easier.

So both internet ip's are on eth0, and I tried manually setting ISP2 as an
alias for ISP1, giving me eth0 and eth0:0 under ifconfig. This allows me to
ping both ip's from my FW, but only ISP1 is pingable from the internet.
I am assuming it is a routing issue, where requests coming in on ISP2 try to
go back out via ISP1's default route.

I am using iptables 1.2.6a (also shorewall.net's shorewall 1.3.14)

I have spent a week reading docs and about routing, but am too much of a
rookie to figure this out. So I am hoping someone can help me out more than
referencing to more docs I don't understand.

I tried DNATting one internet ip to another, not knowig if that is even
possible, using something like

Iptables -t nat -A PREROUTING -d 209.181.237.230 
	-j DNAT --to-destination  24.106.62.180

But to no avail. Iptraf shows I am hitting 209.181.237.230 on eth0, but the
pinging/telnetting clients on the internet never get a reply from my
machine.

I'd appreciate it extra much if I'd get a CC on my shorewall at incisoft dot
com address.

Thanks,
Fonz