DNS and Routers

Hello list,

We have a customer that uses UUNET via an ISP-supplied router to have mails
delivered to his Exchange server (dial-up). The UUNET mail server is
functioning as a smart host for Exchange. This router is directly connected
to the internal network. The Exchange machine has its def. gw set to this
router.

There is an ISA box in the network that was added long after the UUNET
router. The clients default-gateway to ISA and also are setup as web proxy
clients. ISA runs a DNS server, as does the Exchange machine (synchronizing
internal zones). The external interface is connected to a second router that
manages a DSL dod connection.

The DNS problem with the clients registering themselves with ISA instead of
the DC left aside (we will take care of that seperately), my first thought
was to connect both routers to the external interface of the ISA box and let
the default gateway point to the DSL router.

We could then ping the UUNET router to initiate mail transfer to the
Exchange. This would work just fine. As to outgoing mails, as far as I know
the UUNET smart host will only function when it receives mails from within
the UNET network (this would be fairly common). Alternatively, we could also
configure exchange to deliver mails directly over DSL to the recipient's
MXes but since we have a variable IP there, some mails will be rejected.

Is there any way to tell Exchange or ISA how to handle this? I was thinking
of a manual route that routes all traffic on the UUNET subnets to the UUNET
router, but this would be prone to errors, for instance when addresses or
ranges change.

Thanks for listening and thanks for helping
Mark

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