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Ask questions and share experiences with SD-WAN and Session Smart Router (formerly 128T).
  • 1.  Specify specific public IPs for a server's outbound traffic

    Posted 08-01-2019 13:49
    On our Data Center's router we have two ISPs, each with multiple public IPs. I'd like to specify which public IP on each interface is used for our SMTP server, when relaying emails to O365. This will make it easier for the Connector rules in Exchange Online, as well as our SPF record to identify our SMTP server, rather than naming every IP that the SMTP server could be sending mail from in those rules. What would be the best way to configure the Service and Service Route for this? This scenario is kind of backwards from other service routes I've setup.

    Austin Stoffel
    Systems Administrator

  • 2.  RE: Specify specific public IPs for a server's outbound traffic

    Posted 08-06-2019 19:49
    Hey @Austin,

    I haven't seen any way with 128T to specify a unique source-address. I'd be very interested to learn if this can be done with the scenario you described!

    What we've done as a workaround (We are the ISP) - Use a /30 or similar loopback for the WAN Service, then route your public-ips (e.g. a /29) through that loopback. Build a new network-interface and assign it an IP from the routed block.  If your mail server is public, assign it a public-ip from the routed /29 and point it's next-hop to the 128T interface you just created. The 128T router should use service allowing the mail servers public-ip, to with nat disabled.

    If you don't have/want public-ips on your mail server, we've done the above with a firewall/dmz box with the above configuration.

    Surely there's an easier way - if not today maybe soon?​

    Jessie Bryan |
    VP Engineering |