Date: Mon, 14 Jun 1999 08:06:14 -0500 (CDT) From: star@iwl.net To: hackers@FreeBSD.ORG Subject: NAT Gateway to multiple ISPs Message-ID: <199906141306.IAA12874@star1.iwl.net>
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Any ideas on the following ?
I am setting up a home/office network with NAT filtering gateway
on a dual-NIC FreeBSD 3.2 box. No problem so far - I've set
up several like this on 2.2.8 using natd.
The new wrinkle is this: I need to connect to two ISPs
(DSL & Cable Modem), ideally with automatic failover and
load balancing when multiple internal PC's are generating
internet traffic.
I know that this requires running gated (or routed) to
receive RIP or OSPF messages from the ISPs, and to select the
best outgoing ISP's route.
The key question is: while the routing program probably
requires a third NIC so that each external link has its own
device, how can natd handle multiple external internet
interfaces.
I've been searching in several directions:
1) Using "ifconfig alias" option to map the two external
addresses assigned by the two ISPs into the same NIC - would
seem to confuse the routing of outgoing traffic, although I
have 'aliased' reliably on a fbsd web server (all in the same
subnet) and have also seen multiple subnets peacefully coexist
on the same physical network.
2) Somehow get natd or another NAT server to recognise two
outgoing interfaces - this would also seem to confuse the
functioning of the routing program.
3) Configure an internal pseudo-device (tun ?) or divert
interface between natd (and the internal NIC) on the inside
and gated or routed (and the two external NICS) on the
outside.
This way, natd and the routing program would be completely
isolated and wouldn't need to know that the other existed.
ISP1 - NIC1
\
gated - TUN - natd - NIC3 - internal net
/ device
ISP2 - NIC2
The third seems the best choice, but I haven't seen any
discription of this type of configuration.
Any advice ?
Thanks very much for your help,
Andy Starratt
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