Posts Tagged ‘icontests’

Thanks to everyone that participated in Contest #3. Here are the solutions to both questions:

Question 1: eBGP peering with Loopback interfaces

There are actually three possible solutions to this:

  1. Use the neighbor x.x.x.x ebgp-multihop 2 command
  2. Use the neighbor x.x.x.x disable-connected-check command
  3. Use the neighbor x.x.x.x ttl-security hops 2 command

Many people think that it takes two hops to get from the loopback interface of one router to the loopback interface of a directly connected router but this is not true: it actually takes just one hop. You can refer to this article that attempts to clear up this misunderstanding.


Let’s up the stakes for this contest by giving two questions instead of one unlike what we have done for previous contests. This contest will focus on the workings of the Border Gateway Protocol (BGP). The first question deals with how to tweak the default behavior of BGP to suit our needs. The second question presents a troubleshooting scenario which involves BGP.


Contest #2 network

Thanks to everyone who participated in Contest #2 and to those who shared the link. Here is the solution:


Using the network diagram below and the output from the show commands on the routers, identify and resolve why a host on the subnet cannot reach a host with IP address Contest #2 network (more…)

Thanks to everyone that participated and shared the link in some way. Contest #1 is now closed and here is the solution: (more…)

In the network diagram below, there are no routes configured on the routers, yet there should be connectivity among all the routers; therefore, NAT is configured on R1. Zone-based policy firewall (ZBF) is also enabled on R1. TCP, UDP and ICMP traffic should be inspected from the inside to the outside. ICMP from R3 to R2 is the only traffic that should be inspected from the outside to the inside. All other traffic should be dropped.

There are a couple of configuration errors on R1, can you spot them and fix the config? The winner gets 1,500 Naira airtime to any Nigerian phone number. Please read contest rules here. (more…)