They are all in 1 Ethernet segment in the 192.168.1.0/24 network. The OSPF process number, in this case 10, is a user-configurable number which will match at least one of the numbers configured with ipv6 router ospf area tag on an interface. In some design scenarios, you will eventually find more than one routing protocol learning information about destinations. This tutorial is the first part of this article. Each packet transmitted and received over a network contains binary data (ones and zeros that encode the contents of each message). Synchronize the routing protocols at the NetWare server or at the Unix box so they will both understand either RIP or OSPF protocols (as explained in Scenario 3, Step 2). The R3 router ID is 30.30.30.30 (refer to Figure 5). OSPF adjacency process goes through the seven states; OSPF State down, OSPF State Init, OSPF State two ways, OSPF State Exstart, OSPF State Exchange, OSPF State Loading and OSPF State full. chapter are showed the tests done in the described scenarios, reproducing the same problems that could appear in real networks when BGP and OSPF routing protocols are used in the same network. Comprehensive free CCNA lab exercises in a PDF workbook with full solutions covering everything on the latest Cisco CCNA 200-301 exam. 172.16.0.0 – 172.31.255.255. How To | Configure Basic OSPFv3 Scenarios 6 IPv6 router commands awplus-2(config)#router ipv6 ospf 10 This command accesses the OSPFv3 configuration mode. If you completed Lab 9-10 – Configuring OSPF Interface Cost then you should be familiar with how t he metric is calculated by OSPF.The default formula to calculate the cost for the OSPF metric is (10^8/BW). OSPF is easy to understand – once you get over the FIVE BILLION new acronyms and buzzwords that you need to memorise. ; Status. This course helps you prepare for the newest CCNA 200-125 exam, and the CCENT 100-105 exam (ICND1); and the ICND2 200-105 exam. What is BGP? In this article OSPF will be explained in great detail. In a single area all routers must peer with the DR (Designated Router) and BDR (Backup Designated Router if used) for the broadcast domain. Hello Packet: Hello packets are OSPF packet Type 1. We can configure Failover in two modes: Gratuitous ARP on each interface to recalculate L2 subnets. The formula to calculate the cost is Reference Bandwidth divided by interface bandwidth. The devices hello and dead intervals must match. Open: The first message sent after a TCP connection is set up is an Open message, which is used to set up BGP peer relationships. Internet routers are configured to discard any packets coming from the private IP address ranges, so these addresses are not routable on the Internet. The source address of all OSPF messages is always the local end of an adjacency, and all messages are either multicast to one of two reserved multicast addresses, 224.0.0.5 and 224.0.0.6, or unicast to the distant end of an adjacency. OSPF (Open Shortest Path First) The most common use of this routing protocol is to facilitate route updates within a single organization, often to support an IPsec-based distributed network. Each router represents a vertex in the graph. The maximum jitter presented in the transmission using OSPF as a routing protocol is 10.92 ms, more than 1 ms greater than the maximum with the proposal, which presents 9.67 ms. The solution contains the full configuration, so readers without network equipment can still follow the configuration requirements. Instructions -. We will be configuring OSPF in a point-to-point and broadcast type of network and understand the differences between them. One mentions mismatched OSPF process IDs; OSPF process IDs do not need to match for two routers to become neighbors. 2008. router ospf 3 vrf Blue network 0.0.0.0 255.255.255.255 area 0 S2 As OSPF is a link state routing protocol, so it allows to create the neighbor relationship between the routers. The two routers can be neighbors only when they belong to the same subnet, share the same area id, subnet mask, timers, and authentication. I thought it was just like configuring any device for OSPF, however I was wrong. your home LAN or office) 10.0.0.0 – 10.255.255.255. (While primarily used inside a single company, it can span multiple sites.) When a hub and spoke design needs to be deployed using a MPLS VPN, a single CE router functions as the hub router with other CE routers connecting to the hub site over the SP MPLS infrastructure. Configuring OSPF Example for Scenario 7-3 Code View: ROUTER A Router(config)# router ospf 100 Router(config-router)# network 140.100.17.128 0.0.0.15 area 3 Router(config-router)# network 140.100.17.192 0.0.0.15 area 2 Router(config-router)# network 140.100.32.0 0.0.0.0 area 0 Router(config-router)# area 2 stub Router(config-router)# area 3 stub no-summary Router(config … BGP, OSPF, single provider 2 BGP sessions, failover scenario Network diagram is provided below, everything is plugged into a switch (broadcast network) RTP (10.0.0.1/27) AS: 666 OSPF shares information with every router in the network. 37 Full PDFs related to this paper. This process can be explained with the four-layer TCP/IP model, with each step describing the role of the layer. From there, the router builds the FIB with the information in needs to forward the packets including layer 2 … EIGRP According to RFC 2328, Host routes are considered to be subnets whose mask is "all ones (0xffffffff)". Verify that these HELLO parameters match on the neighboring interfaces: OSPF area number - Enter the show ip ospf interface interface-name command in order to check. R2#show ip route. With OSPF, an area border router can sit on the boundary between the backbone area and a low-level area with some interfaces in the area while other interfaces are in the other area. I attended Orhan Ergun’s CCDE training program , used Orhan’s Instructor Led and Self-Paced CCDE training and Online CCDE Practical Scenarios during my CCDE journey. Note the increasing hop count (indicated on the route in parentheses). Based on RFC 2328, it's an open standard. As I understand, forward suppression on Alan, causes the "Forward Address" on the ospf database external to point to 0.0.0.0, which in turn means: when looking for the prefix 1.1.1.0/24 (external network) go to the advertising OSPF router, which is the ABR router translating Type7 LSAs into … In some cases, Rapid Spanning Tree Protocol is similar to STP. 3.2. R1#sh ip route repair 5.5.5.5 Routing entry for 5.5.5.5/32 Known via "ospf 1", distance 110, metric 3, type intra area BGP runs by sending five types of messages: Open, Update, Notification, Keepalive, and Route-refresh. The main difference between OSPF and BGP is that OSPF is an intra-domain routing protocol using link state routing, and the routing operation is performed inside an autonomous system while BGP is the inter-domain routing protocol that uses path vector routing, with the routing operations performed between two autonomous systems. Let me explained. This tutorial explains how to configure OSPF (Open Path Shortest First) Routing protocol step by step in detail. Internet routers are configured to discard any packets coming from the private IP address ranges, so these addresses are not routable on the Internet. 21. Troubleshooting OSPF Route Advertisement(s).pdf from AA 124.06.2016 Troubleshooting OSPF Route Advertisement(s) Search. analyze their performance in different scenario. router ospf 200 network 140.100.13.0 0.0.0.15 area 2 area 2 stub interface FastEthernet0 no ip ospf priority 100 4. If you are not familiar with OSPF, don’t worry ! The routing table of Router R1 shows three networks learnt via EIGRP (denoted as D) and also two directly connected routes denoted as C. For example, destination network 192.168.30.0 is learnt via EIGRP and can be reached via 10.10.10.2 from the Serial0/0/0 interface. Open Shortest Path First (OSPF) uses 'Cost' as the value of metric and uses a Reference Bandwidth of 100 Mbps for cost calculation. Ivan explained how to use the distance command. your home LAN or office) 10.0.0.0 – 10.255.255.255. Departamento de Informática Escola de Engenharia Universidade do Minho _____Tecnologias e Protocolos de Rede, 2015/2016 Tecnologias e Protocolos de Rede [2015/2016] MIEI/MERSTel Laboratory Work TP1: Routing [Part #1] Objectives • Develop initial/basic experiences in the configuration of OSPF and RIP routing protocols. Full State. In IS–IS, routers are entirely within one or the other areas—the area borders are on links, not on routers. CCNP Troubleshooting and Maintaining Cisco IP Networks (TSHOOT v2.0) v1.0 (300-135) Question 1. Scenario 2. In this lesson, i will be discussing different vPC Failure Scenarios, it’s impact on the network and how to solve the problem with Cisco recommended way. FYI I have also included how the metric is calculated at the bottom of each scenario. OSPF and MPLS is most commonly used two technologies in an MPLS VPN environment. I came across this phrase. OSPF Evaluation Sim –> Exacly the same the only difference is that in Question 2 the Answer is: The R1-R3 link needs the neighbor command for the adjacency to stay up. Step 2) Configure BPG and MP-BGP sessions. OSPF (Open Shortest Path First) It is a very famous dynamic routing protocol that is being used in today’s world. This tunnels are in a simple configuration with static routes working well. If you are not familiar with OSPF, don’t worry ! R4(config)# interface Serial0/0 R4(config-if)# ip ospf network point-to-multipoint R4(config-if)# end R4# %SYS-5-CONFIG_I: Configured from console by console %OSPF-5-ADJCHG: Process 1, … Scenario 4 Entry 2 is the correct answer. The protocol that we will select depends on a number of factors. 1. Because OSPF by default advertises these loopback interfaces as /32 routes, hence they will not be matched by prefix-list. A short summary of this paper. It is designed to support large distributed networks via “areas”. OSPF is a link-state routing protocol. Encapsulation. The method for distributing routing information across area boundaries and the importation of external routes into an OSPF routing domain are also explained. Just passed the CCDE Practical exam! The reason why it’s a famous protocol is the fact that it is a standard protocol defined in RFC 2328. As you might have learned in CCNA or CCNP, OSPF will use cost as the metric to choose the shortest path for each destination, this is true but it’s not entirely correct. OSPF is known to be a Not-So-Easy Protocol to Manage and Implement- That's the reason this course has been Introduced. Adjacencies on Point-to-Point Interfaces OSPF will always form an adjacency with the neighbor on the other side of a point-to-point interface such as point-to-point serial lines. OSPF presents an average of 1.51 ms, while the proposal achieves 1.4 ms. A Review Questions section follows each Practical Exercise to ensure that you digest the fundamental terms and concepts presented in each chapter. Discovering secret OSPF information on Cisco routers – Part 1. Synchronize the routing protocols at the NetWare server or at the Unix box so they will both understand either RIP or OSPF protocols (as explained in Scenario 3, Step 2). The forward address is set to 0.0.0.0 which means the router that generated the LSA (R4) is the “next hop”. The main scenario describes TSHOOT.com test bed. OSPF will first look at the “type of path” to make a decision and secondly look at the metric. sumes that the OSPF routing scheme is able to operate with one level of OSPF weights (i.e. Observe how ping packets go back and forth between the two routers, indicating the presence of a routing loop. However the command behavior varies from o­ne protocol to another. You can have multiple OSPFv3 processes, allowing INET version: 4.0. External routes are propagated through an OSPF area as a type 5 from an ASBR, or type 7 LSA from an ASBR in an NSSA. OSPF is easy to understand – once you get over the FIVE BILLION new acronyms and buzzwords that you need to memorise. EIGRP Tutorial – Basic concept explained. Marco Listanti. RFC 4271 defined Next-Hop attribute as follows: The NEXT_HOP is a well-known mandatory attribute that defines the IP address of the router that SHOULD be used as the next hop to the destinations listed in the UPDATE message. Multi area OSPF (Open Shortest Path First) is a way of limiting the amount of neighbors in an area. OSPF Open shortest path first is a dynamic routing protocol which creates a topology between the routers to distribute routing information inside an Autonomous system. Notice that I’m using OSPF as IGP. However, if you have good understanding on vPC and you follow Cisco recommended vPC design, then you can handle Virtual Port Channel (vPC) failure scenarios with confidence. We can see the value of configured timers using the show ip ospf interface command. is used to determine the best path to a destination network is the cost. Allowas-in. OSPFv2 is a link-state routing protocol for IPv4. The minimum-interval statement specifies the minimum transmit … Internet Address 10.0.0.6/30, Area 0. The figure shown below shows the topology we will be configuring. TODO screenshot? OSPF election of Designated Router (DR) DR is select the router with highest priority, if priorities are equal, the highest router-ID wins. In this scenario, we are supposed to configure OSPF on all the routers and at the end of the chapter, we The comprehensive, hands-on guide to all Cisco IOS Software OSPF commands Stands as the complete OSPF command reference -- invaluable for network designers, engineers, and architects Provides configuration, troubleshooting, and verification scenarios for every possible OSPF command supported by Cisco IOS Software that can be implemented on a minimum number of routers Groups OSPF … Marco Listanti. OSPF maintains the view of the network topology conceptually as a directed graph. Each link between neighboring routers represents a unidirectional edge. I believe that Lee is correct in the above statement, according to the following quote from the BSCN book: “The default OSPF mode on a ptp subinterface is ptp mode; the default OSPF mode on a ptm subinterface is nonbroadcast multiaccess mode (p121)”. Configuration Example of MPLS L3VPNs with ISIS Remote LFA 24/Oct/2016. Jitter in ms for each packet in scenario 4. The best practices listed here focus on the most common deployment scenario, but is not intended to preclude the use of alternative topologies. Border Gateway Protocol (BGP) is the postal service of the Internet. The minimum configuration to enable BFD on IBGP sessions is to include the bfd-liveness-detection minimum-interval statement in the BGP configuration of all neighbors participating in the BFD session. One small query. While the RFC3107 “Carrying Label Information in BGP-4” explains this topic in more details, we’ve tried to summarize it and highlight the main ideas. Learn how to enable and configure OSPF routing in Cisco router with practical example in packet tracer. vPC failure scenarios are sometimes destructive. In this post I will share a mini design scenario with you and ask couple questions about the fictitious company architecture. It is a fast converged version of Spanning Tree Protocol as its name implies. After the deployment of OSPF in this network the DES statistics are selected to evaluate the working of OSPF. Ch.6 – OSPF Part 2 of 2: Multi-Area OSPF CCNP version 3.0 Rick Graziani Cabrillo College 2. The area type does not matter. OSPF (Open Shortest Path First) is the most widely used IGP (Interior Gateway Protocol) large enterprise networks. What this means is that all routers (including R3) have to go via R2 in order to reach 200.1.1.1. OSPF area type, such as stub or NSSA - Enter the show ip ospf command in order to check. Peering can change for a variety of reasons, including commercial peering relationships, equipment failures or maintenance. The video demonstrates configuration of OSPF as PE-CE routing protocol in Cisco MPLS VPN. DMVPN Technology and Configuration. OSPF is based on the Shortest Path First (SPF) algorithm which is used to calculate the shortest path to each node. Step 3) Configure PE to CE communication inside a VRF. ASA Failover is intended for improving high availability of the firewall solution. OSPF Path Selection explained. There are three ranges of addresses that can be used in a private network (e.g. OSPF is the industry-standard interior routing protocol designed for use in large networks and makes up approximately nine percent of the BSCI exam. OSPF treats Loopback interfaces as STUB NETWORKS and advertise them as HOST ROUTES (with mask /32) regardless of their configured/native mask. FastEthernet0/0 is up, line protocol is up. OSPF is also an open protocol to ensure that any router or even server operating system can run this protocol. Antonio Cianfrani. Chapter 10, OSPF Hierarchy, begins with a discussion of the restrictions on configuration of OSPF area boundaries. This tutorial explains fundamental and basic concepts of EIGRP Routing protocol including features & characteristics of EIGRP in detail. Learn how OSPF works within a large multiarea network and about the operation of the protocol across OSPF areas. If you completed Lab 9-10 – Configuring OSPF Interface Cost then you should be familiar with how t he metric is calculated by OSPF.The default formula to calculate the cost for the OSPF metric is (10^8/BW). This course is all about Cisco CCNA R&S and everything you need to master your knowledge to become a decorated network engineer.. READ PAPER. OSPF Routing Loop/Sub-Optimal Routing between Cisco IOS and NXOS for External Routes Configuration Example 02/Jul/2014. When you attend to my CCDE class,we will work on tens of scenarios similar to this. C. Node Description Node models are created using Node Editor and then these node models are used for creating instances of node existing in network. When someone drops a letter into a mailbox, the postal service processes that piece of mail and chooses a fast, efficient route to deliver that letter to its recipient. S1 router ospf 1 vrf Red network 0.0.0.0 255.255.255.255 area 0 ! This will guarantee that the routes being advertised by each side will dynamically enter both routing tables. limits the network size that RIP can support. Network Scenario. A particular interface on a router can be part of only a single area which can lead to some issues if the network isn’t designed correctly. Let’s do the same on R2… Let’s now redistribute OSPF into RIP at the Core… Configure the ASA for Redundant or Backup ISP Links 15/May/2015. If we were to just redistribute the 10.10.10.0/24 subnet into EIGRP both MXs would show a more or less equal cost to the destination network of 10.10.10.0/24. Yahoo! These areas are numbered with a dotted quad notation, much like IPv4 addresses. Also, we have another enterprise network (BLUE) with two routers (ENT1 and ENT2). In this scenario, we built a OSPF LSA packet using Scapy (refer to Figure 4) and sent the false information that 11.11.11.0/24 does not exist behind R3 — where the advertising router is equal to the victim router’s ID. For multi instance OSPF you have to use following command: /routing ospf instance print status The best prefixes are fed into the IP routing table or RIB. simulation and measurements are explained further below based on the various models created. We will use a scenario between three routers (R1, R2, and R3) to demonstrate how to Configure Redistribution between RIP and OSPF in Cisco IOS Router. Hi all, I am learning about OSPF and have little or knowledge about WAN network and connectivity. OSPF Multicast Filtering. Note • Optional: This lab coincides with my Multi-area OSPF Lab handout, Rick's OSPF Scenarios (Word doc) • Most of the slides in this presentation do not come directly from CCNP 1 version 3.0, OSPF, but slides which contain a little Network Topology under simulation Fig. This article explained how OSPF routers build neighbor relationships and adjacencies. Are you interested in design aspect of OSPF, many OSPF design examples will… Finally, this chapter covers various issues encountered with routing in real-world OSPF networks and guides you in analyzing and troubleshooting those issues. one weight per link), which is the currently most common scenario, but is also able to provide near-optimal solutions when multiple levels of OSPF weights are used in the network. In this part we explained basic terminology of OSPF such as Feature , Advantage and Disadvantage, Autonomous System, Area concept, ABR, IR, Link, State ,LSA and LSDB with example. In this lesson, i will be discussing different vPC Failure Scenarios, it’s impact on the network and how to solve the problem with Cisco recommended way. In the topology above, RIP is used to connect R1-R2 and OSPF is … It is a great use for MPLS beginners like me. RSTP bypass the Blocking State and Listenning State of STP, and provide Forwarding State in 15 Seconds. This book is written with atypical scenarios about OSPF Protocol explained with another view, in constrast with other resources and the only book in the market that explains OSPF with RFCs Request For Comments, more important, demystifying the different RFC ‘s behavior regarding path selection, NSSA Area options with RFC 1587 and 3101, OSPFv2 and OSPFv3 ‘s behavior when moving from … The main screen consists of two parts; the Main scenario and the Topology tabs. OSPF is an IGP (Interior Gateway protocol) means we can only use it in the same AS (Autonomous System). By this way, an additional feature of the proposed optimization model is the One small query. O SPF (Open Shortest Path First) is a link state routing Protocol, a type of the Internal Gateway Protocol (IGP), which was designed to scale and support more extensive networks.To find … OSPF configuration here is pretty straight forward, as we can simply place all interfaces in area 0 within each VRF. This paper. B. OSPF Scenario Fig.6shows a network that uses the OSPF in all of its routers. We want to configure OSPF over this tunnels for, in a future, establish a dynamic full mesh topology. OSPF- Multi area 1. This course is unlike other CCNA courses as it contains: * Constantly updated and new material to help you prepare. In comparison of IGRP it provides faster convergence times, superior handling of routing loops and improved scalability. You had mentioned that an IGP needs to run at core( that is, between PE routers and P routers - OSPF mostly).This is needed for PE routers to believe that IGP connectivity is available and they can proceed with exchanging the prefixes. The OSPF RID of R4 is 192.168.45.4 which is why we see that in the “Advertising Router” field. Open Shortest Path First (OSPF) is a widely used and supported routing protocol. It's an interior gateway protocol (IGP) meaning it been designed to be used within a single autonomous system. It also falls under the category of Link-state routing protocols. Routers running OSPF learn about the enter network in order to create routes. The two incorrect answers list scenarios that do not cause issues, making them incor- rect answers. So, the convergence time is lower than STP. OSPF Neighborship Condition and Requirement. OSPF is also a link-state routing protocol. 2. 21. To verify the OSPF network type, the command “show ip ospf interface ” can be use. Vincenzo Eramo. DMVPN is a fantastic technology when you’re trying to roll out large-scale site-to-site Internet-based VPN or improve the convergence of your MPLS/VPN-based network. Orhan’s CCDE In Depth book is an excellent summary book … OSPF is a we all know is a link-state routing protocol. Rip and OSPF assignment (RIP ба OSPF дасгал ажил) 1. We saw the OSPF neighbor discovering process via OSPF Hello packets and the role of Link State Requests (LSR) and Link State Updates (LSU). Hi Jeremy, Thanks for the post. Abhishek Verma et al [6] performed survey of RIP and OSPF dynamic Routing Protocols. 192.168.0.0 – 192.168.255.255. This tutorial is the third part of this article. The recommended SD-WAN architecture for most deployments is as follows: MX at the datacenter deployed as a one-armed concentrator. OSPF Type-5 Route Calculation Configuration Example 05/Mar/2015. Notes. View 10. OSPF protocol supports two types of metrics: type1 - ospf metric is the sum of the internal OSPF cost and the external route cost ; type2 - ospf metric is equal only to the external route cost. We also examined the contents of OSPF Hello packets and which fields are necessary to ensure an OSPF adjacency is formed. we have now moved to switching. From the perspective of OSPF, there are a couple of things that must match for a OSPF neighborship to establish; these include: The devices must be in the same area. OSPF Fundamental Terminology Explained. The main objective of a routing protocol is to learn routes, in the scenario of ospf it’s going to learn from his neighbors! All other routers in common broadcast domain … Ideally, they should not overlap and advertise the same destinations, but in some cases, you may find that situation. OSPF is an internal routing protocol. There are three ranges of addresses that can be used in a private network (e.g. Case Study 7 Implementing Hub and Spoke Topologies with OSPF. In this state, the router's interface is looped back to the network in hardware or software. The maximum jitter presented in the transmission using OSPF as a routing protocol is 10.92 ms, more than 1 ms greater than the maximum with the proposal, which presents 9.67 ms. For example, if you have configured ip address 192.168.1.2 255.255.255.240 on an interface, they would enter network 192.168.1.2 0.0.0.15 in the OSPF configuration ... and obviously use one network statement per … You can run all the labs completely for free on your laptop, no additional equipment is necessary. Open Shortest Path First - OSPF. Redistribution can be performed between RIP and OSPF. As you can see we have 6 routers which are all connected to 1 switch. I use a "static" BGP-prefix from our Uplink in my route-map, and I have to redistribute this prefix into OSPF to make the default route work. There is no concept of DR or BDR. The devices must have the same authentication configuration. This LSA is circulated throughout the OSPF domain except for Stub, Totally Stubby and Not-so-stubby areas. Each router in this topology is using an ip address that corresponds to its router number. When you issue the show ip ospf interface command, you notice that there is a discrepancy in the timers on the link between Routers A and B. First before I show how it works and why we need to get some few basic concepts explained. For example, in the case of 10 Mbps Ethernet , OSPF Metric Cost value is 100 Mbps / … 2.1.a MAC learning and aging 2.1.b Frame switching 2.1.c Frame flooding 2.1.d MAC address table Let… Command /routing ospf monitor will display current OSPF status. Step 0) Prerequisite. This document describes IP Unicast Routing configurations supported by the switch, including the principle and configuration procedures of IP Routing Overview, Static Route, RIP, RIPng, OSPF, OSPFv3, IS-IS(IPv4), IS-IS(IPv6), BGP, Routing Policy … During and after a peering change, it is important to confirm reachability to your service from networks around the world. In this scenario (before ospf was actually modified by the people who created the protocol to allow a non-zero value for the forwarding address) only R2 does the redistribution between EIGRP and OSPF. Figure 14-43 shows a SP network implementing hub and spoke using OSPF for Customer A sites. This blog post is more of a challenge situation than a real life example. The other incorrect answer (that is, a scenario that does not cause a problem) mentions the use of two different priority values. The proposed network under simulation In this thesis, three scenarios EIGRP, OSPF and EIGRP_OSPF were created that consists of six interconnected Next scenario, same two routers but different issue: Check out the neighbor adjacency: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 192.168.12.2 1 INIT/DROTHER 00:00:31 192.168.12.2 FastEthernet0/0 R2#show ip ospf neighbor BGP between PE and CE router and its issues. Analyze the election process of DR and BDR using loopback addresses, priority numbers or putting in the router id manually. OSPF Open shortest path first is a dynamic routing protocol which creates a topology between the routers to distribute routing information inside an Autonomous system. Message Encapsulation OSPF operates directly over IP, with a protocol number of 89. You had mentioned that an IGP needs to run at core( that is, between PE routers and P routers - OSPF mostly).This is needed for PE routers to believe that IGP connectivity is available and they can proceed with exchanging the prefixes. OSPF is a link-state routing protocol. Link-state protocols use the shortest path first (SPF) algorithm to populate the routing table. OSPF shares information with every router in the network. OSPF is considered a difficult protocol to configure and requires a thorough understanding of terms that are commonly used. The purpose of the clock rate command is explained in Chapter 2: Static Routes. 172.16.0.0 – 172.31.255.255. I deliberately built the scenario this way to show how a higher-metric route could beat a lower metric for the backup route - of course, in our case, the lower metric would've looped. Auto VPN Best Practices. OSPF presents an average of 1.51 ms, while the proposal achieves 1.4 ms. The other incorrect answer (that is, a scenario that does not cause a problem) mentions the use of two different priority values. VLAN explained with Interview Questions. Download Full PDF Package. OSPF or Open shortest Path first is a dynamic routing protocol that is widely used. The two incorrect answers list scenarios that do not cause issues, making them incor- rect answers. Table of Contents OSPF Unit 1: Introduction to OSPF Unit 2: OSPF We will then redistribute the OSPF routes we’ve learned at the Core from R1 into RIP.