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Chapter 23
Configuring Redundancy
Routing Protocol Peering
In a redundant supervisor engine and dual MSFC configuration, one supervisor engine is fully
operational (active) and the other supervisor engine is in standby mode; however, both MSFCs are
operational (in terms of programming the PFC on the active supervisor engine) and act as independent
routers.
PFC: With the PFC, MLS entries can be associated with either MSFC (based on which MSFC routed
Note
the first packet). Only the PFC on the active supervisor engine switches the packets.
PFC2: With PFC2, only the designated MSFC programs the forwarding information base (FIB), the
Note
adjacency table, Cisco IOS software, and policy routing ACLs on the active supervisor engine. If you
configure static routes or policy routing, you must have the identical configuration on both MSFCs. If
you have a static route on the nondesignated MSFC that is not on the designated MSFC, that route will
not be programmed in the PFC2.
Both MSFCs are operational from a routing protocol peering perspective. For example, if you
have two MSFCs in a single Catalyst 6500 series switch chassis, each configured with interface
VLAN 10 and VLAN 21, the MSFCs are peered to each other over these VLANs. Combined with a dual
chassis and dual MSFC design for the same VLANs, each MSFC has 6 peers: its peer in the same chassis
and the 2 MSFCs in the second chassis (3 in VLAN 10 and 3 in VLAN 21). See
Figure 23-1
VLAN 10
VLAN 21
Although the MSFCs (from a peering perspective) act as independent routers, the two MSFCs in the
chassis operate at the same time, have the same interfaces, and run the same routing protocols.
If you combine high availability on the supervisor engines with HSRP on the MSFCs, you have the
following Layer 2 and Layer 3 redundancy mechanisms:
•
•
OL-8978-04
Dual Chassis and Dual MSFC Peering
Switch 1
Slot 1
Sup#1/MSFC#1
Slot 2
Sup#2/MSFC#2
Layer 2 redundancy for the supervisor engines (one active and one in standby)—If the active
supervisor engine fails (the MSFC installed on it will also fail), both Layer 2 and Layer 3 functions
roll over to the redundant supervisor engine and MSFC combination.
Layer 3 redundancy and load sharing for the two MSFCs—If one MSFC fails, the other MSFC takes
over almost immediately (using HSRP) without any Layer 2 disruption (the active supervisor engine
continues to forward Layer 2 traffic).
Switch 2
Trunk
Slot 1
Sup#1/MSFC#1
Slot 2
Sup#2/MSFC#2
Catalyst 6500 Series Switch Software Configuration Guide—Release 8.7
MSFC Redundancy
Figure
23-1.
23-23
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