Cisco FirePOWER ASA 5500 series Configuration Manual page 236

Configuring Failover
If you have more than one Active/Active failover pair on the same network, it is possible to have the
Note
same default virtual MAC addresses assigned to the interfaces on one pair as are assigned to the
interfaces of the other pairs because of the way the default virtual MAC addresses are determined. To
avoid having duplicate MAC addresses on your network, make sure you assign each physical interface
a virtual active and standby MAC address for all failover groups.
You can configure specific active and standby MAC addresses for an interface by entering the following
commands:
hostname(config)# failover group {1 | 2}
hostname(config-fover-group)# mac address phy_if active_mac standby_mac
The phy_if argument is the physical name of the interface, such as Ethernet1. The active_mac and
standby_mac arguments are MAC addresses in H.H.H format, where H is a 16-bit hexadecimal digit. For
example, the MAC address 00-0C-F1-42-4C-DE would be entered as 000C.F142.4CDE.
The active_mac address is associated with the active IP address for the interface, and the standby_mac
is associated with the standby IP address for the interface.
There are multiple ways to configure virtual MAC addresses on the security appliance. When more than
one method has been used to configure virtual MAC addresses, the security appliance uses the following
order of preference to determine which virtual MAC address is assigned to an interface:
1.
2.
3.
4.
Use the show interface command to display the MAC address used by an interface.
Configuring Asymmetric Routing Support
When running in Active/Active failover, a unit may receive a return packet for a connection that
originated through its peer unit. Because the security appliance that receives the packet does not have
any connection information for the packet, the packet is dropped. This most commonly occurs when the
two security appliances in an Active/Active failover pair are connected to different service providers and
the outbound connection does not use a NAT address.
You can prevent the return packets from being dropped using the asr-group command on interfaces
where this is likely to occur. When an interface configured with the asr-group command receives a
packet for which it has no session information, it checks the session information for the other interfaces
that are in the same group. If it does not find a match, the packet is dropped. If it finds a match, then one
of the following actions occurs:
•
•
Using the asr-group command to configure asymmetric routing support is more secure than using the
Note
static command with the nailed option.
Cisco Security Appliance Command Line Configuration Guide
14-34
The mac-address command (in interface configuration mode) address.
The failover mac address command address.
The mac-address auto command generate address.
The automatically generated failover MAC address.
If the incoming traffic originated on a peer unit, some or all of the layer 2 header is rewritten and
the packet is redirected to the other unit. This redirection continues as long as the session is active.
If the incoming traffic originated on a different interface on the same unit, some or all of the layer
2 header is rewritten and the packet is re-injected into the stream.
Chapter 14 Configuring Failover
OL-10088-01