09-07-2026 03:17 AM
Just wondering if anyone had done any testing with HTTPS inspection on MX? Interested in knowing how it impacted performance as well as any other gotcha's.
Appreciate any replies in advance
09-07-2026 04:14 AM
@Bobcheese2 hi,
There is definite performance drop if the hardware box dont have enough resources. also you may need certificate installation on user PCs for root cert or use public certificate for the enc/decrypt. its recommend to select correct device model using below values.
NGFW Throughput
(Advanced Security - Prevention)
EMIX
09-07-2026 12:43 PM
I tested this a while ago, and it had a 90% performance impact. It reduced the performance of an MX that could do 1000 Mb/s to 100 Mb/s.
Since then, I have been going down the Cisco Secure Access route.
09-08-2026 01:54 AM
Wow. No wonder they aren't publishing those numbers anywhere!
09-08-2026 02:15 AM
Thanks, wondering if the C8xxx have more processor headroom for things like this? Seems a bad decision to add as a feature if it has such an impact on performance (i'm aware of performance hits on other vendor equipment but at least the quote the expected throughput on their DS's). Feels almost like a box ticking exercise?
09-08-2026 07:50 PM
>Seems a bad decision to add as a feature if it has such an impact on performance
Cisco Meraki actually dropped support for this feature. We were all surprised because of the sudden comeback.
I think you are correct. Some contract required that feature, so they bought it back from the dead.
09-08-2026 02:07 AM
There can be a pretty noticeable performance hit with MX HTTPS inspection, especially on higher-throughput links. Cisco rates on-box TLS decryption as a high performance-impact feature, and certificate trust plus certificate-pinned applications are common gotchas.
09-08-2026 07:27 AM
Regarding other gotchas, don't overlook (from OP reference):
What traffic should be bypassed?
Administrators should consider bypassing business-critical applications that use certificate pinning, destinations that fail during inspection, and any traffic excluded for privacy, regulatory, or operational reasons.
Rember, this is basically a man-in-the-middle "attack".
Nor:
Supported TLS 1.3 traffic can be inspected, but TLS 1.3 sessions using Encrypted ClientHello (ECH) are bypassed rather than decrypted.
Basically, your going down the path, somewhat, like recording all phone communications or placing cameras in company provided rest rooms. I.e. sometimes you need to consider legalities beyond what's possible technically.
From a security viewpoint, if you're concerned about what might be exchanged via HTTPS, what about flash drives and personal cell phones?
BTW, I'm not discounting the issue, just sometimes folk don't appreciate the full picture nor considerations beyond the technical.
As engineers, further recognize your employer may tell to do something that's actually illegal and the fact you, or your employer, are unaware of that, doesn't necessarily protect you.
Over the years, I've been in companies presented with devices to "inspect" encrypted data communications, and whenever I asked for further validation of its legality, the project was dropped.
Again, not saying this should never be done nor it's always illegal, but proceed with care. If nothing else, it can cause bad will with employees. So, just a possible "gotcha" besides concern about performance impact.
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