Dell PowerConnect J-EX4200-24T Software Manual page 2336

Dell PowerConnect J-Series Ethernet Switch Complete Software Guide for Junos OS
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Figure 47: VoIP Multiple Supplicant Topology
If an 802.1X-compatible IP telephone does not have an 802.1X host but has another
802.1X-compatible device connected to its data port, you can connect the phone to an
interface in single-supplicant mode. In single-supplicant mode, the 802.1X process
authenticates only the first supplicant. All other supplicants who connect later to the
interface are allowed full access without any further authentication. They effectively
"piggyback" on the first supplicant's authentication. For an example of a VoIP single
supplicant topology, see Figure 48 on page 2265 .