RE: External Network Logic
- From: "Steve Moffat" <steve@xxxxxxxxxx>
- To: "ISA Mailing List" <isalist@xxxxxxxxxxxxx>
- Date: Wed, 7 Dec 2005 20:59:57 -0400
Thank god for that.........
-----Original Message-----
From: Thomas W Shinder [mailto:tshinder@xxxxxxxxxxx]
Sent: Wednesday, December 07, 2005 8:58 PM
To: ISA Mailing List
Subject: [isalist] RE: External Network Logic
http://www.ISAserver.org
OK, in that case, there won't be any NAT, since the external network
isn't available because you'll have no route of last resort. NAT is
never enforced unless you want it to be.
Tom
Thomas W Shinder, M.D.
Site: www.isaserver.org
Blog: http://spaces.msn.com/members/drisa/
Book: http://tinyurl.com/3xqb7
MVP -- ISA Firewalls
> -----Original Message-----
> From: Thor (Hammer of God) [mailto:thor@xxxxxxxxxxxxxxx]
> Sent: Wednesday, December 07, 2005 6:42 PM
> To: [ISAserver.org Discussion List]
> Subject: [isalist] RE: External Network Logic
>
> http://www.ISAserver.org
>
> This isn't a back-to-back config. This is a single server going in
> between my clients and my servers... There won't be a way to "NAT to
> the Internet"
> in that config as the only defined rule will be a route relationship
> from the Perimeter to the Internal.
>
> I understand the concept that "Internet" is is the default gateway,
> but in this case, there can't be a "Nat" relationship anywhere.
> t
>
>
> ----- Original Message -----
> From: "Thomas W Shinder" <tshinder@xxxxxxxxxxx>
> To: "[ISAserver.org Discussion List]" <isalist@xxxxxxxxxxxxx>
> Sent: Wednesday, December 07, 2005 4:25 PM
> Subject: [isalist] RE: External Network Logic
>
>
> http://www.ISAserver.org
>
> No, the Internet is always there, unless you're talking about a
> caponized ISA firewall (single NIC).
>
> The Internet is reached via the NIC with the default gateway
> defined on
> it, which in a back to back config would be the internal interface of
> the FE ISA firewall.
>
> There is one point of confusion induced by the UI -- and that's the
> ability to create an "external Network". There is no difference from
> the firewall's point of view between a perimeter Network and
> an external
> Network. So, you can create another external Network if you like, but
> its *exactly the same* as a perimeter network from ISA's
> multinetworking
> point of view. The default External Network is always there
> (except for
> the unihomed ISA firewall).
>
> For example, if a client on the default Internal Network connects to a
> host on the perimeter network between the ISA firewalls, the
> connections
> are routed and the source IP address is not replaced. If a host on the
> default internal Network connects to an IP addresses that is
> part of the
> default External Network (which is the Internet) the
> connection will be
> NATed.
>
> The ISA firewall's ability to enable control over your route
> relationships really does give you a lot of flexibility.
>
> Thomas W Shinder, M.D.
> Site: www.isaserver.org
> Blog: http://spaces.msn.com/members/drisa/
> Book: http://tinyurl.com/3xqb7
> MVP -- ISA Firewalls
>
>
>
> > -----Original Message-----
> > From: Thor (Hammer of God) [mailto:thor@xxxxxxxxxxxxxxx]
> > Sent: Wednesday, December 07, 2005 5:39 PM
> > To: [ISAserver.org Discussion List]
> > Subject: [isalist] RE: External Network Logic
> >
> > http://www.ISAserver.org
> >
> > One thing though, just so I understand-- How would I NAT to
> > the Internet?
> > There *is no* "Internet" per se in a 2 NIC config with both
> > defined as ISA
> > Firewall Networks, right? There would be route
> relationship from the
> > Internal to the DMZ Perimeter. The Internet would only exist if an
> > Interface was added and not defined elsewhere, correct?
> > t
> >
> > ----- Original Message -----
> > From: "Thomas W Shinder" <tshinder@xxxxxxxxxxx>
> > To: "[ISAserver.org Discussion List]" <isalist@xxxxxxxxxxxxx>
> > Sent: Wednesday, December 07, 2005 3:01 PM
> > Subject: [isalist] RE: External Network Logic
> >
> >
> > http://www.ISAserver.org
> >
> > The default External Network is defined as all addresses that
> > defined by
> > any other ISA firewall Network. So, there is still an
> > external network,
> > you just don't have any access to it, since you've created
> > ISA firewall
> > Networks for both the NIC (one for the default Internal
> > Network and one
> > for the ISA firewall Network representing the perimeter
> network NIC).
> >
> > You can use this in a number of scenarios, like turning the
> > DMZ between
> > the BE and FE ISA firewall into an ISA firewall Network and
> creating a
> > route Network Rule between that and the default Internal
> Network, but
> > still NAT'ing to the Internet. Pretty slick, eh?
> >
> > Thomas W Shinder, M.D.
> > Site: www.isaserver.org
> > Blog: http://spaces.msn.com/members/drisa/
> > Book: http://tinyurl.com/3xqb7
> > MVP -- ISA Firewalls
> > **Who is John Galt?**
> >
> >
> >
> > > -----Original Message-----
> > > From: Thor (Hammer of God) [mailto:thor@xxxxxxxxxxxxxxx]
> > > Sent: Wednesday, December 07, 2005 4:57 PM
> > > To: [ISAserver.org Discussion List]
> > > Subject: [isalist] External Network Logic
> > >
> > > http://www.ISAserver.org
> > >
> > > So, you've got ISA with 2 NIC's. You define the Internal
> > > range on one NIC,
> > > leaving the other NIC as "External." You then add a
> > > perimeter network, and
> > > give it the IP range of what used to be the "External" NIC.
> > > What happens to
> > > the concept of the External network since you now have a
> > > trusted Internal
> > > network and a less trusted "Perimeter" network, but no real
> > > "External"
> > > network anymore. Will it just be an "empty" network set
> > > sitting there all
> > > alone in the cold, cold ground?
> > >
> > > t
> > >
> > >
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