Cisco WS-X6066-SLB-APC - Content Switching Module Software Manual page 253

Chapter 14 Configuring MLS
Understanding the MLS Cache
These sections describe the MLS cache:
•
•
•
•
•
MLS Cache
The PFC maintains a Layer 3 switching table called the MLS cache for Layer 3-switched flows. The
cache also includes entries for traffic statistics that are updated in tandem with the switching of packets.
After the PFC creates an MLS cache entry, packets identified as belonging to an existing flow can be
Layer 3 switched based on the cached information. The MLS cache maintains flow information for all
active flows.
Unicast Traffic
For unicast traffic, the PFC creates an MLS cache entry for the initial routed packet of each unicast flow.
Upon receipt of a routed packet that does not match any unicast flow currently in the MLS cache, the
PFC creates a new MLS entry.
Multicast Traffic
For multicast traffic, the PFC populates the MLS cache using information learned from the MSFC.
Whenever the MSFC receives traffic for a new multicast flow, it updates its multicast routing table and
forwards the new information to the PFC. In addition, if an entry in the multicast routing table ages out,
the MSFC deletes the entry and forwards the updated information to the PFC.
For each multicast flow cache entry, the PFC maintains a list of outgoing interfaces for the destination
IP multicast group. The PFC uses this list to identify the VLANs on which traffic to a given multicast
flow should be replicated.
These MSFC IOS commands affect the multicast MLS cache entries on the switch:
•
•
MLS Cache Aging
The state and identity of flows are maintained while packet traffic is active; when traffic for a flow
ceases, the entry ages out. You can configure the aging time for MLS entries kept in the MLS cache. If
an entry is not used for the specified period of time, the entry ages out and statistics for that flow can be
exported to a flow collector application.
78-13315-02
MLS Cache, page 14-5
Unicast Traffic, page 14-5
Multicast Traffic, page 14-5
MLS Cache Aging, page 14-5
MLS Cache Size, page 14-6
Using the clear ip mroute command to clear the multicast routing table on the MSFC clears all
multicast MLS cache entries on the PFC.
Using the no ip multicast-routing command to disable IP multicast routing on the MSFC purges
all multicast MLS cache entries on the PFC.
Catalyst 6000 Family Software Configuration Guide—Releases 6.3 and 6.4
Understanding How Layer 3 Switching Works
14-5