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2 External NICS for ISP switch over? - 18.Dec.2003 12:24:00 AM

wildman

Posts: 7
Joined: 25.Sep.2001
From: Melbourne, Australia
Status: offline

Hi.
I hope someone can help me out here. I have an ISA server with three NICS, 2 external, one internal.

I am not trying to do fail over or NLB with them and only want to use a single NIC for internet access. Currently each NIC is connected to a different ISP, one old, one new. One is in building ethernet, one sHDSL, both with a single static IP.

I do, however want to use both NIC's for inbound data, specifically SMTP to allow a transparent cross over during DNS propogation and no loss or delay of mail. Once the DNS changes are complete, I will then change the config to use only the new ISP link.

I have added duplicate server publishing rules for SMTP, Exchange RPC, VPN connections and OWA. I think my problem is that the ISA box is using a single NIC for the return data (the old connection) so when trying to connect over the new connection, no TCP acknowledgement packets are going back along the same link thus no connection is being made. Both external NIC's have a gateway, but I have set the metrics on the NIC's to use the old ISP link for the moment. I have not lost internet connectivity. The ISA Server is aware of it's third NIC and external IP address. The new ISP link works perfectly when plugged directly into a machine but I am unable to connect into the office via the new link. I have added a ping response packet filter for the new IP address but I am not getting any response from an external machine.

Does anyone have a method for switching ISP's while connected to both, without downtime, that can be done with a dual External NIC system?

Thanks
Ben

Post #: 1

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RE: 2 External NICS for ISP switch over? - 19.Dec.2003 1:14:00 AM

AHIT

Posts: 1561
Joined: 22.Jul.2002
From: Sydney, Australia
Status: offline

ISA can't support dual external interfaces simultaneously.. largely also because W2K and W2K3 can't support multie default routes. Only one interface can be the default.

If your DNS is hosted offsite create a 2nd MX record pointing to the new IP address. Give it a while to propogate (depending on your refresh intervals etc) and create all teh packet filters etc in ISA.
Then simply flick over the default gateway to the new link. All your amil should start using the 2nd MX record and still be delivered. Then update DNS to reflect correct hostnames etc and all's done.

3d party products like rainfinity are supposed to allow multiple links simultaneously but honestly I've never tried it as it was somewhat pricey from memory. That being said, I run 2 ISP's consurrently on one ISA box. I just have a default route to ISP1 and then a static route to teh entire range for ISP2 through it's NIC. The are a backup MX (4th in priority) so that even if something does go horribly wrong here with ISA/power/whatever, they queue the mail and when we're backup and all gets spewed down the line to us.

Hope this helps..

(in reply to wildman)

Post #: 2

RE: 2 External NICS for ISP switch over? - 20.Jan.2004 10:27:00 PM

wildman

Posts: 7
Joined: 25.Sep.2001
From: Melbourne, Australia
Status: offline

Thanks for the suggestions Tolk.

What I ended up doing was building a complete second ISA box temporarily and configuring it completely for the new link. Once I was happy with it, I scripted it, moved the connection to the proper ISA box and applied the rules. Luckily, our setup delivers all our mail to a public mail server in a datacentre (we provide mail for clients) and the forwards it in to Exchange for the office. I edited the hosts file on the external machine to give the new office location, restarted it services, pushed in queued mail and it was fine. Total mail interruption around 20 minutes.

Cheers.
Ben

(in reply to wildman)

Post #: 3

RE: 2 External NICS for ISP switch over? - 26.Jan.2004 9:29:00 PM

JohnBullinger

Posts: 53
Joined: 25.Apr.2003
From: Texas
Status: offline

quote:
Originally posted by Tolk:
ISA can't support dual external interfaces simultaneously.. largely also because W2K and W2K3 can't support multie default routes. Only one interface can be the default.

If your DNS is hosted offsite create a 2nd MX record pointing to the new IP address. Give it a while to propogate (depending on your refresh intervals etc) and create all teh packet filters etc in ISA.
Then simply flick over the default gateway to the new link. All your amil should start using the 2nd MX record and still be delivered. Then update DNS to reflect correct hostnames etc and all's done.

3d party products like rainfinity are supposed to allow multiple links simultaneously but honestly I've never tried it as it was somewhat pricey from memory. That being said, I run 2 ISP's consurrently on one ISA box. I just have a default route to ISP1 and then a static route to teh entire range for ISP2 through it's NIC. The are a backup MX (4th in priority) so that even if something does go horribly wrong here with ISA/power/whatever, they queue the mail and when we're backup and all gets spewed down the line to us.

Hope this helps..

Tolk,

Can you tell me how your using two ISP's?? What I want to do is to have two ISP's and if one goes down I want to be able to use the other one. This doesnt need to be a automatic switch or anything like that, if I have to do it manually (easily though in case someone non technical has to do it) that would work also? I mainly need to keep connectivity between my two offices.

Thanks

John

(in reply to wildman)