Configure Layer 2 Switching features Nexus

Configure Layer 2 Switching features Nexus

Posted on Jan 24, 2020 (0)

Configure Layer 2 Switching features Nexus

Frame Switching between Segments:

When the L2 Frame needs to be switched between segments, switch lookup its address table to find where the destination MAC is connected to. To switch frames between LAN, each switch maintains an address table called as CAM table or MAC table.

This table is populated dynamically when any L2 frame enters on port, switch Port captures the MAC address of the frame and populates the CAM table with MAC address, its associated port and interface to which this host is connected.

When a frame has destination address as FF.FF.FF.FF then it is treated as broadcast frame and the switch will flood this broadcast frame to all its ports that belong to same VLAN.

We have also option to configure MAC address called as Static MAC address, which statically points to specified interface on switch and also on both devices which are connected by VPC Peer link. These static MAC address overrides the dynamic learned MAC address on that interface. Broadcast MAC address are not configured however Multicast MAC address can be configured as static MAC address.

All MAC address tables on each module should exactly match MAC address table on supervisor but if yu want to see the missing and extra MAC address entries use the below commands:

N7K1# config t
N7K1(config)# mac address-table static 0000.000a.1123 vlan 2 interface ethernet 1/1

Configure Static MAC address on Layer -3 Interface.

N7K1# config t
N7K1(config)# interface ethernet 6/3
N7K1(config-if)# mac-address 22ac.47ad.ff39

Show forwarding consistency L2

Now from NX-OS 4.2 onwards MAC address can also be statically configured for all L3 interfaces. IF you want to know what is the default MAC address for Layer 3 interface? , it is VDC MAC address.

A static MAC address can be configured on following Layer-3 interface.

  • A Layer 3 Interface
  • A Layer 3 Sub interface
  • A Layer 3 Port-Channel

But you cannot configure Static MAC address on tunnel interface.

License Requirement for L2 Switching

For Layer 2 switching, there is no additional license required.


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