802.1x question

Brian Julin BJulin at clarku.edu
Tue Aug 7 07:00:38 CEST 2018

zhang zhi-heng <zhzhang.sg at gmail.com> wrote:
> Or, in order to pass MAC "and" certificate, it will not be compliant with
> 802.1x since 802.1x only uses x.509 certificate and therefore we would need
> a switch with 802.1x "bypass mode"?

MAC-authentication-bypass mode is used to help clients that cannot do 802.1x.
You should not need it to do 802.1x with an 802.1x-capable client.

With a client that does 802.1x, the RADIUS server will have the MAC address
usually because the RADIUS NAS adds extra fields (Calling-Station-Id) and sends
them along with the EAP request.  The client does not send these, they are added
by the NAS (switch).

When a NAS authenticates a client on a wired port, either by MAB or 802.1x, it usually
allows all traffic from the MAC address (Calling-Station-Id).  (For IP first hop
security use the normal ARP/DHCP/IP protections, or whatever extra features
the switch supports for downloadable ACLs.)

However, even though the MAC address is what is used to permit or deny
access, it is kept track of using a Session-Id distinct from the MAC address,
and the session usually only applies to a single port on the switch.  Exactly
how the NAS and the RADIUS backend handle a MAC showing up on multiple
ports differs by vendor, as does the available features for multiple clients
on the same port.  These are what you need to pay attention to when
evaluating switches.  Nothing beats a test drive.  Also be sure to test wake-on-lan
and sleeping machines in your typical deployment environment if you have them.

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