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Here is a break-down of anonymous outer identity support for some popular EAP types:
| EAP-Type | Support for anonymous outer identites |
|---|---|
| EAP-TTLS | yes |
| PEAP | yes |
| EAP-FAST | yes |
| EAP-TLS | support in protocol, but not typically available in supplicants |
| EAP-PWD | no |
If the EAP type allows for the use of outer identities, it is a client device configuration option to either make use of them or not; there is little you as an IdP can do to force the use of anonymous outer identities (except for providing and encouraging the use of pre-configured installers which will then make all the necessary settings on the client device automatically).
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Now, assuming you have the option of configuring a range of EAP types *and* your clients support that same range, which of these types should you prefer?
- We suggest the use of PEAP over EAP-TTLS for it does a mild amount of protection of the user password inside the secure tunnel.
- If you cannot support PEAP, consider to allow TTLS-PAP and the more unusual variant TTLS-GTC (initially Generic Token Card; also used for passwords which are not savable on the client device). Some older devices (certain Symbian OS builds) support TTLS, but not PAP inside. Enabling TTLS-GTC will allow these devices to connect.