Cisco WS-X6066-SLB-APC - Content Switching Module Software Manual page 495

Chapter 22 Configuring Redundancy
Both MSFCs are operational from a routing protocol peering perspective. For example, if you
have two MSFCs in a single Catalyst 6000 family 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
as well as the 2 MSFCs in the second chassis (3 in VLAN 10 and 3 in VLAN 21). See
Figure 22-1 Dual Chassis and Dual MSFC Peering
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:
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).
The Layer 3 entries programmed by the failed MSFC on the active supervisor engine are used until they
gracefully age out and are replaced by the Layer 3 entries populated by the newly active MSFC. Aging
takes 4 minutes and allows the newly active MSFC to repopulate the MLS entries using its XTAG value,
while concurrently hardware-switching flows yet to be aged. In addition, this process prevents a newly
active MSFC from being overwhelmed with initial flow traffic.
Each MSFC has its own XTAG value to identify itself as the MLS Route Processor. MSFC #1 (on the
Note
active supervisor engine) has an XTAG of 1, and MSFC #2 (on the standby supervisor engine) has
an XTAG of 2.
Only Supervisor Engine 1 uses the XTAG values; XTAG values are not used on Supervisor Engine 2.
For same-chassis Layer 3 redundancy to function as expected, the configuration on each MSFC must
Caution
be the same (see
78-13315-02
Switch 1
Trunk
Slot 1
Sup#1/MSFC#1
Slot 2
Sup#2/MSFC#2
Table 22-2 on page
Switch 2
Slot 1
Sup#1/MSFC#1
Slot 2
Sup#2/MSFC#2
22-20).
Catalyst 6000 Family Software Configuration Guide—Releases 6.3 and 6.4
MSFC Redundancy
Figure 22-1.
22-21