Cisco WS-C6506 Software Manual page 718

MSFC Redundancy
You can achieve further load sharing by using MSFC #2 in Switch S1 as the primary HSRP router for
VLAN 12 and MSFC #2 as the primary HSRP router in Switch S2 for VLAN 23 (see
Figure 23-3
HSRP Active VLAN 10: priority 110
HSRP Standby VLAN 21: priority 108
HSRP Standby VLAN 12: priority 109
HSRP Standby VLAN 23: priority 107
HSRP Standby VLAN 10: priority 109
HSRP Standby VLAN 21: priority 107
HSRP Active VLAN 12: priority 110
HSRP Standby VLAN 23: priority 108
Only the active HSRP router for a VLAN will respond with the HSRP MAC address for ARP requests
to the HSRP IP address. The active HSRP router will in turn ARP for the end stations' MAC address and
populate its ARP cache. By using both MSFCs in a single chassis to share the HSRP duties for the even
VLANs, you can share the control plane ARP traffic. In an MSFC failure, only the ARP entries on the
affected VLAN would need to be relearned.
The tradeoff for this level of redundancy and load sharing is the added complexity of keeping track of
the even and odd VLANs on the MSFCs within a Catalyst 6500 series switch chassis.
The MLS entries are created for the packets arriving at the HSRP MAC addresses and those packets
arriving with the router's real MAC addresses. HSRP is used for unicast traffic first-hop redundancy; for
traffic that is received through another router attached to VLAN 10, for example, the actual MAC address
of Sup #1/MSFC #1 is used.
Understanding Failure Scenarios
These five examples describe the possible failure scenarios within a single chassis with dual supervisor
engines and dual MSFCs (see
refers to the MSFC that is used to program the ACL ASIC for the static ACLs.
Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
23-26
Dual MSFC Operational Model for Redundancy and Load Sharing—
VLANs 10, 12, 21, and 23
VLAN 10/21
Trunk 1
Switch S1
Slot 1
Sup#1/MSFC#1
Slot 2
Sup#2/MSFC#2
Figure
VLAN 12/23
Trunk 2
Switch S2
Slot 1
Sup#1/MSFC#1
HSRP Standby VLAN 10: priority 108
HSRP Active VLAN 21: priority 110
HSRP Standby VLAN 12: priority 107
HSRP Standby VLAN 23: priority 109
Slot 2
Sup#2/MSFC#2
HSRP Standby VLAN 10: priority 107
HSRP Standby VLAN 21: priority 109
HSRP Standby VLAN 12: priority 108
HSRP Active VLAN 23: priority 110
23-4) when you enable high availability. The designated MSFC
Chapter 23 Configuring Redundancy
Figure 23-3).
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