ASR1000 Box to Box HA with Zone-based Firewall: Config

The ASR 1000 series routers have the ability to be deployed in an highly-available design, a solution called Box to Box HA or Inter-chassis Redundancy.  One of the benefits to the ASR is you can stack  Zone-based Firewall (ZBFW) on top of it.  To deploy a highly-available ASR with ZBFW, in a WAN to LAN topology requires asymmetric routing support due to the nature of a stateful firewall.  At the time of writing this there is a lack of information regarding design and config options for this scenario. I plan to address those issues here.

The documentation regarding the design and configuration required to deploy Box to Box HA with ZBFW on the ASR platform is unclear.  In addition there is a bug which requires a configuration workaround.

-Two Cisco ASR1001-4x1GE (Total of 8 x 1GE SFP ports per ASR)
-IOS XE 3.6.1.S ....  ( IOS 15.2(2)S1 ) 
-Advanced IP Services License, Firewall License, Firewall/NAT Stateful Inter-Chassis Redundancy License
-Two /30 hand-offs from ISP
-LAN consists of redundant Cisco Nexus switches using vPC technology

-Security Configuration Guide: Zone-Based Policy Firewall, Cisco IOS XE Release 3S (ASR 1000)

-Bug CSCub03015

Design Options
The first gotcha is (at this point in time) the LAN has to use a switch stack to have a full mesh design.  You can not do full mesh and use Cisco's vPC technology seen on the Nexus line or plain old redundant switches for your LAN.  The good news is with the help of Cisco (TAC, SE's, TME's, and DE's) we came up with this solution.  In the process we uncovered a bug (which they have a workaround for). 

Next, in addition to purchasing the Firewall Feature License, you will need to purchase the Firewall/NAT Stateful Inter-Chassis Redundancy License.  Also, note the firewall won't work if you have IP Base, Advanced IP Services or higher is required.


To get a baseline of the configuration concepts, I recommend reading the "Interchassis Asymmetric Routing Support for Zone-Based Firewall and NAT" section of the config guide referenced above.  To achieve similar redundancy to a full mesh design but with non-stackable switches requires us to add another link between the ASR's (we will call it the Routed link).  Above shows the key configuration and wiring required for this to work.  Attached here is the detailed config for both ASR's.  Note: there are a handful of places you can add link redundancy with Port-channels.  However this will be limited on the number of ports based on the ASR model you have.  I chose to show the option with the least ports used.  The key point above is to keep the same breakdown and not to stack any traffic types (exception is Control and Data).  In the end the only difference between this design and using stackable switches on the LAN is the full mesh design can survive two kitty-corner device failures.  For example, you could lose ASR1K-A and SWITCH-B, or vice versa and still be up.  This is because with a switch stack for the LAN we would just run a cross-stack etherchannel from each ASR and life would be grand (in theory/per Cisco, I haven't tested).  

Results and Conclusions
With this configuration we are able to achieve a similar level of redundancy to a full mesh design with out the use of stackable switches.