Owner's Manual

Switched Port Analyzer (SPAN) and Remote Switched
Port Analyzer (RSPAN)
When you enable SPAN or RSPAN, port traffic is copied and sent to the specified uplink port that hosts
the monitoring appliance. If you enable RSPAN, monitored traffic is also tagged with the specified VLAN
ID. If you enable SPAN, no tags are added to the monitored traffic.
The controller advertises all external ports as potential edge ports. You can configure any potential edge
port as a mirrorTo port or a monitor port. Use the GUI or REST APIs to define the policy for monitored
traffic or specify the port for monitored traffic by associating a policy.
Virtual Link Trunking (VLT)
In a typical VLT topology, a connected pair of switches is known as a VLT pair and the link between them
is an interconnect link. A VLT pair in a network topology acts as a single logical switch for all entities
connected to both switches. The ports connected to the VLT pair are known as VLT ports. The switches
within the VLT pair are also known as head nodes and the switches connected to the VLT pair are known
as leaf nodes.
Forwarding Database (FDB)
A forwarding database (FDB) entry learned on a VLT port is configured on the equivalent VLT port on the
VLT pair switch. In traditional networks, both switches in the VLT pair run a protocol to synchronize their
FDB entries. Instead of using a protocol, AFC configures the FDB entries learned on one VLT port on the
corresponding VLT port. If the leaf nodes are part of the fabric, the controller forms the port channel by
including all leaf node ports connected to the VLT pair. If the leaf nodes are legacy switches connected
to the fabric through uplink ports, the controller is notified that the legacy switch connected to the fabric
switches using VLT. Alternatively, you can enable LACP on the legacy switches using uplinks to connect
to the fabric .
Link Aggregation Control Protocol (LACP)
To identify VLT topologies in the fabric, you must enable LACP on the legacy switch for the controller . If
you do not configure LACP on the legacy switches, or if you enabled NIC teaming on the server without
LACP, the controller must be notified of the VLT connectivity from the external entities. By default, the
controller listens for LACP packets on all fabric edge ports. If an LACP packet is received on the uplink
port, the controller checks if a port channel can be configured. When it receives an LACP packet from the
same entity on two different neighboring switches in the fabric, the controller responds with a virtual
MAC address. Using this method, the controller can identify the VLT-compatible connectivity with a
legacy switch. This also applies if the leaf nodes connected to the VLT pair are NIC teaming servers.
After the VLT pair is identified, the controller identifies the VLT ports and equivalent ports. After the port
roles are identified, the controller configures VLT blocking on each of the VLT pairs to prevent data loops
and duplicate packets. VLT blocking blocks all traffic from the interconnect link to the VLT port. If the leaf
nodes are part of the fabric, the controller creates port channels on the leaf nodes. After pushing the VLT
blocking configuration, the controller populates the FDB entries on the equivalent port when an FDB
entry is learned on a VLT port.
Supported Technologies and Protocols
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