Guidelines And Limitations For Switching Modes - Cisco Nexus 3000 Series Configuration Manual

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
• Cisco Nexus 3500 Series switches do not support switching modes in Cisco NX-OS Release 7.0(3)I7(2)
• Packets with frame check sequence (FCS) errors are dropped.
• Packets with FCS errors are not mirrored if SPAN is configured.
Store-and-Forward Switching Mode Guidelines and Limitations
• Packets 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
• The store-and-forward mode activates automatically for a port when the switch identifies that the ingress
Cisco Nexus 3000 Series NX-OS Layer 2 Switching Configuration Guide, Release 6.x
50
and later releases.
• 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.
errors are dropped.
rate is less than the switching capacity of the egress port. For example, when the port ingress rate is 1
GB, the switching capacity of the egress port is 10 GB.
Cisco Nexus 3000 Series switches perform cut-through switching if the bits are serialized-in at the same
or greater speed than they are serialized-out.
In-Out
1 GB to 1 GB
1 GB to 10 GB
1 GB to 40 GB
10 GB to 1 GB
10 GB to 10 GB
Configuring Switching Modes
Cisco Nexus 3000 Switching Mode
cut-through
store-and-forward
store-and-forward
cut-through
cut-through
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