Cisco Systems N3KC3048TP1GE, N3KC3064TFAL3 manual Guidelines and Limitations for Switching Modes

Configuring Switching Modes

Guidelines and Limitations for Switching Modes

Because it waits to forward the frame until the entire frame has been received and checked, the switching speed in store-and-forward switching mode is slower than the switching speed in cut-through switching mode.

Guidelines and Limitations for Switching Modes

Consider the following guidelines and limitations for each of the switching modes:

Cut-Through Switching Mode Guidelines and Limitations

•Packets with frame check sequence (FCS) errors are dropped. For example:

•For the Cisco Nexus 3064PQ platform, packets smaller than or equal to 768 bytes are dropped.

•For Cisco Nexus 3016, 3064E, 3064X, and 3048 platforms, packets smaller than or equal to 560 bytes are dropped.

•For the Cisco Nexus 3064PQ platform, packets larger than 769 or equal to bytes are forwarded.

•For 3016, 3064E, 3064X, and 3048 platforms, packets larger than or equal to 561 bytes are forwarded.

•Packets with FCS errors are not mirrored if SPAN is configured.

Store-and-Forward Switching Mode Guidelines and Limitations

•Packets that are smaller than the maximum transmission unit (MTU) size configured on the switch with FCS errors are dropped.

•Packets with FCS errors are not mirrored if SPAN is configured.

•The CPU port always operates in store-and-forward mode. Any packets forwarded to the CPU with FCS errors are dropped.

•Store-and-forward mode activates automatically for a port when the switch identifies that the port is oversubscribed and the ingress rate is greater than the switching capacity of the egress port. For example, when the port ingress rate is 10 gigabit and the switching capacity of the egress port is 1 gigabit.

Note The global configuration does not change, even if store-and-forward mode is activated for an oversubscribed port.

Licensing Requirements for Switching Modes

Cut-through switching mode and store-and-forward switching modes do not require licenses. Any feature not included in a license package is bundled with the Cisco NX-OS system images and is provided at no extra charge to you. For a complete explanation of the Cisco NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.

	Cisco Nexus 3000 NX-OS Layer 2 Switching Configuration Guide, Release 5.0(3)U3(1)
60	OL-26590-01