14-10
Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
OL-8978-04
Chapter 14 Configuring MLS
Understanding How Layer 3 Switching Works
This example shows how the show mls entry command output appears in source-destination-ip mode:
Console> (enable) show mls entry ip short
Destination-IP Source-IP Prot DstPrt SrcPrt Destination-Mac Vlan
--------------- --------------- ----- ------ ------ ----------------- ----
ESrc EDst SPort DPort Stat-Pkts Stat-Byte Uptime Age
---- ---- ----- ----- --------- ------------ -------- --------
171.69.200.234 171.69.192.41 - - - 00-60-70-6c-fc-22 4
ARPA SNAP 5/8 11/1 3152 347854 09:01:19 09:08:20
171.69.1.133 171.69.192.42 - - - 00-60-70-6c-fc-23 2
SNAP ARPA 5/8 1/1 2345 123456 09:03:32 09:08:12
Total Entries: 2
* indicates TCP flow has ended
Console> (enable)
With the full-flow flow mask, because a separate MLS entry is created for every ip flow, the details are
shown for each flow.
This example shows how the show mls entry command output appears in full flow mode:
Console> (enable) show mls entry ip short
Destination-IP Source-IP Prot DstPrt SrcPrt Destination-Mac Vlan
--------------- --------------- ----- ------ ------ ----------------- ----
ESrc EDst SPort DPort Stat-Pkts Stat-Byte Uptime Age
---- ---- ----- ----- --------- ------------ -------- --------
171.69.200.234 171.69.192.41 TCP* 6000 59181 00-60-70-6c-fc-22 4
ARPA SNAP 5/8 11/1 3152 347854 09:01:19 09:08:20
171.69.1.133 171.69.192.42 UDP 2049 41636 00-60-70-6c-fc-23 2
SNAP ARPA 5/8 1/1 2345 123456 09:03:32 09:08:12
Total Entries: 2
* indicates TCP flow has ended
Console> (enable)
Partially and Completely Switched Multicast Flows
Some flows might be partially Layer 3 switched instead of completely Layer 3 switched in these
situations:
• The MSFC is configured as a member of the IP multicast group (using the ip igmp join-group
command) on the RPF interface of the multicast source.
• The MSFC is the first-hop router to the source in PIM sparse mode (in this case, the MSFC must
send PIM-register messages to the rendezvous point).
• The multicast TTL threshold is configured on an egress interface for the flow.
• The extended access list deny condition on the RPF interface specifies anything other than the
Layer 3 source, Layer 3 destination, or IP protocol (an example is a Layer 4 port number).
• The multicast helper is configured on the RPF interface for the flow, and multicast to broadcast
translation is required.
• Multicast tag switching is configured on an egress interface.
• Network address translation (NAT) is configured on an interface, and source address translation is
required for the outgoing interface.
For partially switched flows, all multicast traffic belonging to the flow reaches the MSFC and is software
switched for any interface that is not Layer 3 switched.
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