How many untagged VLANs can be configured on an EX Series switch port?

On an EX Series switch port, only one untagged VLAN can be configured. This untagged VLAN is designated as the native VLAN for the port, which is the VLAN that will handle traffic that does not contain any VLAN tags. In typical network configurations, this untagged VLAN ensures that devices that do not support VLAN tagging can still communicate across the network without any issues.

It's important to recognize that while multiple VLANs can be configured on a switch port using tagging (also known as trunking), only one can exist in an untagged state. This is necessary for maintaining clarity and functionality in the network, as allowing multiple untagged VLANs would lead to ambiguity regarding how traffic should be handled.

This understanding of the single untagged VLAN is critical for network design and troubleshooting, ensuring that configurations align with established networking standards.