SSL VPN Split Tunneling and Office 365
UPDATE: Apr 9, 2020 A colleague, Vinicius M. , put together a Configuration guide:
Optimizing Office 365 traffic on Remote Access through VPNs when using BIG-IP APM.pdf
Optimizing Office 365 traffic on Remote Access through VPNs when using BIG-IP APM.pdf
As we shift to a much larger remote workforce than ever before, additional strains are being placed on the remote access infrastructure of many organizations around the world.
Over the past several weeks we have seen organizations adapt quickly, and as it relates to APM, implement split tunneling configurations to specifically allow Office 365 traffic to egress a client's local interface instead of the corporate network via the VPN tunnel. Microsoft publishes their Office 365 endpoints (URLs & IPs) via an API but occasionally they make changes and keeping on top of those changes can be an administrative nightmare.
To make the ongoing maintenance of the Network Access Lists / split tunneling configuration as seamless as possible, I’ve adapted a Python script (see GitHubRepo) we commonly use for SSL Orchestrator deployments to fetch Office 365 endpoints and update one or more Network Access Lists. Used in conjunction with iCall, this script will periodically check for and apply updates to your Network Access List(s) without any administrative intervention, allowing you to focus on other mission critical tasks.
The script is maintained and documented in this GitHub repository: https://github.com/f5regan/o365-apm-split-tunnel
Microsoft has provided us with a statement concerning their recommendations for Office 365 and split tunneling:
"Microsoft recommends excluding traffic destined to key Office 365 services from the scope of VPN connection by configuring split tunneling using published IPv4 and IPv6 address ranges. For best performance and most efficient use of VPN capacity, traffic to these dedicated IP address ranges associated with Office 365 Exchange Online, SharePoint Online and Microsoft Teams (referred to as Optimize category in Microsoft documentation) should be routed directly, outside of the VPN tunnel. Please refer to Microsoft guidance for more detailed information about this recommendation."
Microsoft’s recommendations have been incorporated into the script published in the aforementioned GitHub repository. See the changelog for details.
More Resources
In addition to considering how the steps in this article may relieve some strain on your organization’s remote access infrastructure, I’d highly recommend visiting How to optimize SSL VPN connections when BIG-IP is reaching 100% CPU for further guidance on optimizing SSL VPN connections.
Updated Jun 16, 2022
Version 2.0
ReganAnderson
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GeoffGAltostratus
The access policy and NA is being updated ok but I still need to "Apply" the access policy so it won't take effect until this is done is all.. Just needs my manual intervention.
Also, adding the URLs to the script includes them in the DNS exclusion. Which is fine as this is the intended functionality of the script but in my case this would likely mean the routing table on the client could potentially be very long as a result.. I believe each entry from the DNS Exclusion list is resolved and then added in as a host route.
I'm not actually sure Microsoft has an endpoint specifically of windows update like it seems they do for O365.
Thanks very much for your replies too. This script in any event is great and much appreciated.
Cheers
ReganAndersonThe Access policies/profiles defined in the "access_profiles" list (line 40) should be applied (on or around line 386) when the script is executed. If you have them defined but they aren't applying, make sure you don't have a typo in the name.
- GeoffG
Thanks very much I have been playing around on my testbed. One thing I have noticed is I need to apply the Access policy after the update is working. maybe I have missed something(probably 😉 ) but is there another step I need to take o make sure this is applied to the Network Access List automatically ?
Cheers and thanks again
- ReganAnderson
I'm not aware of a published list of IPs used for Windows Update but Microsoft has published a list of Windows Update URLs here: https://docs.microsoft.com/en-us/windows/deployment/update/windows-update-troubleshooting#device-cannot-access-update-files
You would have to verify with Microsoft whether these URLs are subject to change but assuming it is fairly static list you could simply add these addresses to the "additional_urls" list in the script.
- GeoffG
Very useful and really well done.
Was wondering if there was something similar for Microsoft windows Updates along the same lines?
Cheer and thanks for the share
SmithyCirrostratus
you can find that here: https://github.com/f5devcentral/f5-office365-ip-url-automation
PeteWhiteDead simple - I’ll take a look at changing this script to update a datagroup Regards Peter White T: 07785 456991
Dan_PachecoCirrus
Hiya,
I am looking for a similar functionality (retrieve MS IP and subnet list), but instead of updating the APM network access list, I want it to automatically update an LTM IP data-group. Any idea where I might find such a thing?
Thanks,
- PeteWhite
Great job Regan - I have translated this into an iApp which installs the script and creates an iCall to update daily at https://devcentral.f5.com/s/articles/SSL-VPN-Tunnel-and-Office-365