Comparing internal routing protocols (IGPs)

The following table lists the differences between the three most popular interior routing protocols: FeatureRIPEIGRPOSPFTypedistance vectorhybriddistance vectorMetrichop countbandwidth and delaycostSpeed of convergenceslowfastfastRoutingclassful (RIPv1), classless(RIPv2)classlessclasslessUpdatesperiodical broadcast (RIPv1), multicast(RIPv2)multicastmulticastManual summarizationno (RIPv1), yes (RIPv2)yesyesSupported on non-Cisco routersyesnoyesConfiguration complexityeasymediumhard Prerequisites Read more [...]

Differences between OSPF and EIGRP

The following table lists the differences between OSPF and EIGRP: Prerequisites for 200-301 200-301 is a single exam, consisting of about 120 questions. It covers a wide range of topics, such as routing and switching, security, wireless networking, and even some programming concepts. As with other Cisco certifications, you can take it at any of the Pearson VUE certification centers. The recommended training program that can be taken at a Cisco academy is called Implementing and Administering Cisco Read more [...]

OSPF summary

Here is a list of the most important OSPF features:link state routing protocolclassless routing protocolsupports VLSM (Variable Length Subnet Mask)converges fastuses the concept of areasuses multicast address for routing updates (224.0.0.5 and 224.0.0.6)sends partial routing updatessupports only equal cost load balancingmanual summarization can be done only on ABRs and ASBRsuses interface cost as a metricuses SPF algorithm to calculate the best pathsopen standardeach router inside an area has the Read more [...]

OSPF authentication

OSPF can be configured to authenticate every OSPF message. This is usually done to prevent a rogue router from injecting false routing information and therefore causing a Denial-of-Service attack.Two types of authentication can be used: 1. clear text authentication – clear text passwords are used 2.  MD5 authentication – MD5 authentication is used. This type of authentication is more secure because the password doesn’t go in clear-text over the network.NOTE With OSPF authentication Read more [...]

OSPF summarization

Route summarization helps reduce OSPF traffic and route computation. OSPF, unlike EIGRP, doesn’t support automatic summarization. Also, unlike EIGRP, where you can summarize routes on every router in an EIGRP network, OSFP can summarize routes only on ABRs and ASBRs.The following command is used for OSPF summarization:(config-router) area AREA_ID range IP_ADDRESS MASKTo better understand OSPF summarization, consider the following example network:All three routers are running OSPF and exchanging Read more [...]

Designated & Backup Designated Router

Based on the network type, OSPF router can elect one router to be a Designated Ruter (DR) and one router to be a Backup Designated Router (BDR). For example, on multiaccess broadcast networks (such as LANs) routers defaults to elect a DR and BDR. DR and BDR serve as the central point for exchanging OSPF routing information. Each non-DR or non-BDR router will exchange routing information only with the DR and BDR, instead of exchanging updates with every router on the network segment. DR will then Read more [...]

OSPF configuration

Configuring OSPF 1OSPF basic configuration is very simple. Just like with other routing protocols covered so far (RIP, EIGRP) first you need to enable OSPF on a router. This is done by using the router ospf PROCESS-ID global configuration command. Next, you need to define on which interfaces OSPF will run and what networks will be advertised. This is done by using the network IP_ADDRESS WILDCARD_MASK AREA_ID command from the ospf configuration mode.NOTE The OSPF process number doesn’t have Read more [...]

OSPF overview

OSPF (Open Shortest Path First) is a link state routing protocol. Because it is an open standard, it is implemented by a variety of network vendors. OSPF will run on most routers that doesn’t necessarily have to be Cisco routers (unlike EIGRP which can be run only on Cisco routers).Here are the most important features of OSPF:a classless routing protocolsupports VLSM, CIDR, manual route summarization, equal cost load balancingincremental updates are supporteduses only one parameter as the Read more [...]