Cisco N7K-C7010 Configuration Guide - Page 86

Information About Access and Trunk Interfaces Chapter 3 Configuring Layer 2 Interfaces Send document comments to [email protected] To optimize the performance on access ports, you can configure the port as a host port. Once the port is configured as a host port, it is automatically set as an access port, and channel grouping is disabled. Use the host designation to decrease the time that it takes the designated port to begin to forward packets. Only an end station can be set as a host port; you will receive an error message if you attempt to configure other ports as hosts. If an access port receives a packet with an 802.1Q tag in the header other than the access VLAN value, that port drops the packet without learning its MAC source address. A Layer 2 interface can function as either an access port or a trunk port; it cannot function as both port types simultaneously. When you change a Layer 2 interface back to a Layer 3 interface, that interface loses all the Layer 2 configuration and resumes the default VLAN configurations. IEEE 802.1Q Encapsulation Note For information about VLANs, see the Cisco Nexus 7000 Series NX-OS Layer 2 Switching Configuration Guide, Release 5.x. A trunk is a point-to-point link between the switch and another networking device. Trunks carry the traffic of multiple VLANs over a single link and allow you to extend VLANs across an entire network. To correctly deliver the traffic on a trunk port with several VLANs, the device uses the IEEE 802.1Q encapsulation, or tagging, method that uses a tag that is inserted into the frame header (see Figure 3-2). This tag carries information about the specific VLAN to which the frame and packet belong. This Cisco Nexus 7000 Series NX-OS Interfaces Configuration Guide, Release 5.x 3-4 OL-23435-03