Campus Fabric Layer 2 considerations
In the CB (core) stack, Layer 2 forwarding is performed on the local unit. However, forwarding decisions for PE unit ports are made in the CB, not locally on the PE.
MAC learning is disabled in Campus Fabric PE units.
The CB stack maps each E-tag E-CID and its associated physical port to a virtual port. The CB supports Layer 2 forwarding between virtual ports and between virtual and physical ports. The CB is responsible for programming MAC addresses associated with the PE units for forwarding traffic to the PE units in the Campus Fabric domain.
VLAN filtering is performed in the CB. This means that on CB physical and virtual ports:
- Tagged packets (with a matching VLAN) are allowed on an untagged port.
- Untagged or priority tagged packets on a tagged port are not allowed and are dropped.
- All tagged, untagged, and priority tagged packets are allowed on dual-mode ports.
By default, each PE port is guaranteed membership in a maximum of four VLANs, including
the default VLAN. You can increase the number of allowable memberships per PE port
to any value from 5 through 1024 using the
max-vlan-per-pe-port command. The potential pool for configuring PE VLAN contains 4096 entries and does
not include the four default VLANS provisioned for the PE. Pool counters begin to
increment only with the fifth VLAN. Use the
show spx pe-port-vlan-resource command to check the number of available entries. The current non-default
max-vlan-per-pe-port
setting is displayed in
show running-config command output.
The following table summarizes Layer 2 feature support available in a Campus Fabric domain.