Using Redundant Interfaces

One of the things that I love about the ASA is that there are so many variations in the way it can be configured.  You can run in transparent or routed mode, single or multiple context mode and even do fancy things with sub-interfaces.  A somewhat new configuration that I see pop up from time-to-time is the use of redundant interfaces.  I’ve heard people call it an interface bundle, and some other fancy names.  Redundant interfaces are a very simple concept.

The begin with, the concept of a “virtual” Redundant interface.  This is in the form of interface Redundant#.  The Redundant interface is where the IP address, nameif, and physical member interface definitions are defined.  In the following output you can see a simple configuration where E0/1 and E0/2 are members of the Redundant Interface 1.  Some things to consider here are that you need to remove any configuration on the physical interfaces and VLANS and Spanning-tree should be a consideration for the interfaces of the switch were you’re connected.

!

interface Redundant1

member-interface Ethernet0/1

member-interface Ethernet0/2

ip address 172.23.22.11 255.255.255.0

nameif inside

Now once you take a look at the interface after you’ve made it redundant you can see which interface is actively being used. Traffic is not load balanced across the two links.

ciscoasa(config-if)# show interface redundant1 | begin Redundancy

Redundancy Information:

Member Ethernet0/1(Active), Ethernet0/2

Last switchover at 22:54:36 UTC May 6 2010

ciscoasa(config-if)#

Additionally you can easily change which interface is active:

ciscoasa(config-if)# redundant-interface redundant 1 active-member Ethernet0/2

And with verification you can see that this has taken place.

ciscoasa(config-if)# show interface redundant1 | begin Redundancy

Redundancy Information:

Member Ethernet0/2(Active), Ethernet0/1

Last switchover at 22:56:46 UTC May 6 2010

ciscoasa(config-if)#

Redundant interfaces are definite possibility on the CCIE Security Exam so be aware of them and prepared to configure them.

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Tags: CCIE Security, redundant interfaces