rib2routem

Python tool to convert IOS-XR RIB to routem configuration file for easy replay in the lab. It leverages Cisco pyATS to parse IOS-XR RIB output.

Introduction

In order to test router's FIB, a common technique is to use a traffic generator such IXIA or Spirent and generate prefixes. While this is fast and easy to do, this doesn't represent customers' network reality.
rib2routem is a tool used to:

• parse a production router RIB (show route ipv4 unicast, show route ipv6 unicast)
• extract prefixes, next-hop
• generate a routem configuration file to replay the RIB in a lab

routem

routem is an old-school and proprietary Cisco tool to generate control plan. If you search hard enough on Internet, you'll find copies. routem can be configured to replay a RIB, using ASCII file. In this mode, 2 configuration files are required.

Establishing BGP peering with routem

RIB is replayed via a simple BGP session between SUT and routem. Following sample configuration is used for IPv4 unicast:

router bgp 65537
bgp_id 1.63.51.21
neighbor 1.63.51.51 remote-as 65537
neighbor 1.63.51.51 update-source 1.63.51.21
capability ipv4 unicast
capability refresh
capability 4bytes-as
replay file LER.IPv4.cfg ascii

Note the last line of this configuration file: this is where prefixes are stored.

Replay prefixes

The replay file has following minimal format and requires BGP mandatory attributes:

 advertised 1.0.0.0/24
 origin igp
 aspath

next-hop inherits neighbor IP.

RIB input

RIB is collected from customer's network with CLI. Output is stored in a txt file. genie offline parsing capacity is used to extract prefixes, next-hop, etc. The tools supports both IPv4 and IPv6. See https://pubhub.devnetcloud.com/media/genie-feature-browser/docs/#/parsers/show%2520route%2520ipv4 and https://pubhub.devnetcloud.com/media/genie-feature-browser/docs/#/parsers/show%2520route%2520ipv6.

Generating routem replay file: rib2routem utilisation

1. Get 'show route ipv4 unicast' or 'show route ipv6 unicast' output and store it in a .txt file
2. Edit both python files to point to the .txt file location
3. Execute rib2routem and redirect to a file

python3 rib2routem.py > LER-v4.cfg

Todo

• One file to handle both IPv4 and IPv6.
• Add next-hop support

Acknowledgements

I'd like to thanks Antoine Orsoni for his support. You can check Antoine's work on xrdocs.io website: https://xrdocs.io/programmability/tutorials/pyats-series-parsing-like-a-pro/