LDAPS Falling back to LDAP

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LDAPS Falling back to LDAP

L1 Bithead

Our firewalls are configured for LDAPS on port 636 to our Windows DC. We have the require SSL/TLS option checked in the LDAP settings window. The useridd log shows:


2022-03-22 14:42:09.136 -0700 connecting to ldap://[dcserver]:636 with StartTLS...
2022-03-22 14:42:09.140 -0700 connecting to ldaps://[dcserver]:636 ...
2022-03-22 14:42:09.164 -0700 ldap cfg domain - LDAP connected to dcserver:636( index 0)


However, the DC server acting as LDAPS server is showing event ID: 2085 in Directory Service log with data: "the client and server cannot communicate, because they do not possess a common algorithm."


The firewall appears to working as expected, but the LDAPS server is throwing these warnings. How can I address the event ID warnings on the LDAPS server?



L5 Sessionator

Have you run a packet capture on the DC to see what cipher suites are being offered from the PA?

Hey @LeeSeeman ,

It is strange to see "do not possess a common algorithm" with modern PanOS and Win Server versions.

What version of PanOS and DC are you running?


I don't believe there would be any difference, but have you tried to use port 389 in LDAP server profile in addition to "require TLS/SSL" enabled. As you can see from documentation it seems that 389 + require SSL/TLS  should use StartTLS



I am surprised to see in your logs "2022-03-22 14:42:09.136 -0700 connecting to ldap://[dcserver]:636 with StartTLS.."

Anyway again it doesn't make a lot of sense to have a difference, but way want to try.

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