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Frame Relay – Understanding Static and Dynamic Mappings
This is the solution for quiz-13 that covers Frame Relay, a topic that is very hard to find it implemented in today's networks but often seen during certification exams, as it still part of the curriculum for some of them. This is about differences between static and dynamic frame relay mappings.
Quiz #16 – BGP Filtering Updates
Company ABC is in process of configuring BGP Confederations between its sites. During a small transition period, there will be no BGP between R3 and R2, but instead only static routing. Have a look at the quiz and try answering the question !
Quiz #15 – RIPv2 Problems after Link Failure
Your network is up and running without any complaints for few months. All good, until one single link creates problems in the entire network, although it was supposed to be redundant. What's wrong ?
OSPF – Understanding the Forwarding Address (FA)
Here I come with the solution for quiz-12, that I consider to be one of the most difficult quizes published on this blog, until now. Forwarding Address (FA) is not quite a common nor easy to understand topic. Read to find out more.
Quiz #14 – Default Originate into OSPF
Your network follows a standard 3 tier hierarchical design (Core, Distribution, Access) and has two WAN circuits with eBGP sessions with the ISPs. You want to push the default route down to the Distribution routers, but something goes wrong. Where is the mistake?
NAT – Order of Operation
This post represents the solution and explanation for quiz-11. A very important topic when configuring Network Address Translation (NAT) is the order of operation. Who is performed first: NAT or Routing ?
Quiz #13 – Frame Relay self pinging
You have recently joined a new company that still uses Frame Relay. For monitoring purposes, you implement a script that pings all interfaces of a router, but you notice that some of them are not ping-able. Why ?
OSPF on PE-CE Links and the Understanding the Down Bit
This post represents the solution and explanation for quiz-10. It describes the functionality of the Down Bit in preventing routing loops in your network.
Quiz #12 – OSPF Improper Path Selection
Company ABC closes a deal with a Partner Company that requires redundant network paths between the two networks. Two connections are installed between the companies, but the traffic seems to go over the slower one. Why ?
Protecting the BGP Session with MD5 Authentication
This post represents the solution and explanation for quiz-9. There are some challenges to allow an authenticated MD5 BGP session via a firewall, involving TCP Options. Let's see what happens!
Quiz #11 – NAT both Source and Destination
Your company makes a new contract with a Partner Company for a new research project. To provide network connectivity, NAT is being configured on your side but something does not work as desired. What is it?
MPLS LDP-IGP Synchronization
This post represents the solution and explanation for quiz-8. Adding a new link into the MPLS cloud created an outage for the customer. Read to understand how LDP-IGP Synchronization might help.
Quiz #10 – OSPF on CE-PE links
Company ABC has multiple offices interconnected via an MPLS provider and each office runs OSPF with a separate Area number.
In one of the offices, there is an internal router that uses VRFs. You notice that some routes are not learned. Why ?
Catalyst MLS QOS – part I
This post represents the solution and explanation for quiz-7. The junior network administrator tried to update the configuration on a switch by enabling mls qos and immediatelly created an outage. See what happened !
Quiz #9 – BGP peering over a Cisco ASA
Your company has 2 offices that are interconnected via a firewall (Cisco ASA) as shown below. You received the task to configure a BGP session between the border routers but something does not go according to plans.
Recursive Routing with Tunnels – study case: GRE over IPsec
This post represents the solution and explanation for quiz-6. Running dynamic routing protocols over tunnels can result in recursive problems. Read more to understand the problem and some solutions.
Quiz #8 – MPLS: inside Provider’s Core
You are a network engineer of a company that provides MPLS services to more customers. Your teams tries to increase the redundancy, but instead they receive complaints that connectivity is broken. What's wrong?
Quiz #7 – MLS QOS
You have recently moved to a new company as a network administrator and you've started doing an audit of the existing network. Your network uses an end-to-end QOS approach between multiple offices. Access switches trust QOS markings received from IP Phones and higher layer devices trust the markings received from access switches, as seen in diagram below.
OSPF – P-bit Setting in Type-7 LSAs
This post represents the solution and explanation for quiz-5.
It explains one of the Loop Prevention mechanisms in OSPF by using the P-bit in the LSA.
Quiz #6 – Routing protocols over IPsec
Your company is extending their network with a Remote Office in a different city. You configure an IPsec tunnel between the HeadQuarters and the Remote Office, then you run EIGRP over it, but soon you find out that the tunnel flaps up and down continuously. What is the problem?