Posted on by and filed under RuCTF Quals 2014.

For this challenge, we are given a set of Cisco router configs as well as a visual topology. The challenge is to find a missing config line in R1.

Configurations

Reviewing the configs, there was only one typo, but for the most part it worked. There was a clue about a static route on R3 being used on the network. When lost, always review the documentation. A quick search about “Cisco router OSPF EIGRP” brought me to a page about using a router to bridge networks on these two different networks.

http://www.cisco.com/c/en/us/support/docs/ip/enhanced-interior-gateway-routing-protocol-eigrp/8606-redist.html

After learning some cool stuff about each of these routing protocols, I noticed one config line that seems to not exist in the challenge.

Clue

redistribute eigrp 1 subnets to match the ID of oud EIGRP config. This was the key!