03-05-2012 03:06 PM
I have a need to split the traffic going to and coming from my Exchange server based on service. Currently I have both SMTP and 443 traffic coming into and going out of the same ISP (we'll call it A). ISP A is also the default for all incoming and outgoing traffic. I want to split this to have SMTP traffic coming and going through ISP B and leave the 443 traffic on ISP A.
I think I can do this with PBF rules but I'm not totally sure how to go about it. If so here are some questions that I have.
Do I need to create 1 PBF or 2? Incoming and outgoing or just outgoing?
Do I need to create NAT rules for the PBF traffic? I already have NAT for the stuff on ISP A.
Do I need to create regular policies in addition to the PBF. eg. allowing incoming port 25 etc.
Or, am I barking up the wrong tree. I looked at the document for branch office with two ISP's and there are similarities here, but I only want to do this for the one service and not use it for failover at this time.
Thanks in advance,
Kenton
03-05-2012 03:20 PM
Hi...Yes, you can use PBF to do what you described. My comments are inline:
Do I need to create 1 PBF or 2? Incoming and outgoing or just outgoing?
- You can have 1 PBF rule but the rule would be 'any any service=tcp/25'. I recommend using 2 PBF rules for inbound & outbound to match the IP address of your mail server(s).
Do I need to create NAT rules for the PBF traffic? I already have NAT for the stuff on ISP A.
- Yes, you need NAT rule and most likely, you need to use ISP-B's assigned IP address.
Do I need to create regular policies in addition to the PBF. eg. allowing incoming port 25 etc.
- If ISP-A and ISP-B are in the same security zone, then you can leverage your existing security rules.
Thanks.
03-05-2012 03:20 PM
Hi...Yes, you can use PBF to do what you described. My comments are inline:
Do I need to create 1 PBF or 2? Incoming and outgoing or just outgoing?
- You can have 1 PBF rule but the rule would be 'any any service=tcp/25'. I recommend using 2 PBF rules for inbound & outbound to match the IP address of your mail server(s).
Do I need to create NAT rules for the PBF traffic? I already have NAT for the stuff on ISP A.
- Yes, you need NAT rule and most likely, you need to use ISP-B's assigned IP address.
Do I need to create regular policies in addition to the PBF. eg. allowing incoming port 25 etc.
- If ISP-A and ISP-B are in the same security zone, then you can leverage your existing security rules.
Thanks.
03-05-2012 03:23 PM
Thanks for the quick reply. I'll post back if I have any additional questions once I get going on it.
Kenton
03-05-2012 04:13 PM
So would my two PBF rules look like this?
Direction Source Zone Source Server Destination Service Egress I/F
Outgoing Trusted Mail Server Any SMTP ISP B
Incoming Untrusted Any ISP B Pub SMTP Internal
Thanks,
Kenton
03-05-2012 05:40 PM
Yes, the outgoing PBF rule looks good. Make sure that your service=SMTP is where SMTP=tcp/25.
I just realized that we can't control the incoming. Senders will be sending to your mail server 'smtp.company.com' and this domain will resolve to the IP address on your ISP-A. So all incoming traffic will come in the current path.
Thanks.
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