ISE Closed Mode L2 Protocols

[dm2020]

Hi All,

I'm unable to test this at the moment and I cant find much info in Cisco documentation.

Does anyone know if L2 protocols are still received/transmitted on a closed mode port, specifically STP and CDP?

Thanks,

[Colby LeMaire · Accepted solution]

Looks like only EAPOL, STP, and CDP are the only L-2 protocols/traffic that can pass when a port is unauthorized.  Here is a quote from documentation:

"Until the client is authenticated, 802.1x access control allows only Extensible Authentication Protocol over LAN (EAPOL), Cisco Discovery Protocol (CDP), and Spanning Tree Protocol (STP) traffic through the port to which the client is connected. After authentication is successful, normal traffic can pass through the port."

This was found in the following documentation:  https://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst3750x_3560x/software/release/12-2_55_se/configuration/guide/3750xscg/sw8021x.html

Keep in mind that by default, DHCP and DNS are also allowed unless a different ACL is applied to the port configuration.