Cisco 6500 - Catalyst Series 10 Gigabit EN Interface Module Expansion, Configuration Manual, Page: 173 / 742

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Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Configuration Guide using ASDM
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Chapter 8 Configuring IP Routing and DHCP Services
Configuring Asymmetric Routing Support
Adding Interfaces to ASR Groups
Enter the following commands to add an interface to an asymmetric routing group. Stateful Failover
must be enabled for asymmetric routing support to function properly between units in failover
configurations.
hostname/ctx1(config)# interface if
hostname/ctx1(config-if)# asr-group num
Valid values for num range from 1 to 32. You need to enter the command for each interface that will
participate in the ASR group. You can create up to 32 ASR groups and assign a maximum of 8 interfaces
to each group.
Note
The upstream and downstream routers must use one MAC address per VLAN and have different MAC
addresses for different VLANs to allow for the redirection of packets from a standby unit to an active
unit in failover configurations.
Asymmetric Routing Support Example
Figure 8-1 shows an example of using the asr-group command for asymmetric routing support in an
Active/Active failover configuration.
Figure 8-1 ASR Example with Active/Active Failover
Context A is active on one unit and context B is active on the other. Each context has an interface named
“outside”, both of which are configured as part of
asr-group 1. The outbound traffic is routed through
the unit where context A is active. However, the return traffic is being routed through the unit where
context B is active. Normally, the return traffic would be dropped because there is no session information
Failover/State link
132916
ISP A
Inside
network
Context A
interface Ethernet4
nameif outside
asr-group 1
Context B
interface Ethernet2
nameif outside
asr-group 1
Outbound Traffic
Return Traffic
ISP B
FWSM
FWSM