4. Best path selection in multiple protocol environment with – RIPv2, EIGRP and OSPF

Dynamic routing protocol can decrease administrative overhead in large network environment. But what path will be selected for data traveling from point A to point B. Today published scenario will take closer look at path selection process in „academic“ multi protocol environment. 

Routing protocols that we can found in intra domain routing environment can be break down into two distinct category.

1. Distance vector routing protocols (RIPv1, Ripv2, IGRP, EIGRP) – advertisements about remote network are periodic, full or only affected parts of routing table (routing by rumor principe) – route is propagated as „route sign“ network „198.120.24.0/24“ and path to „serial0/1/0 or next hop 198.20.0.4/30“.

2. Link state routing protocols (OSPF, IS IS) – after link state data flooding at startup or after trigger (change in network environment) is created independently in appropriate router full network topology (OSPF use Edgar Dijkstra Shortest path first algorithm for it).

Routing protocols use for path selection and their next routing table introduction their own mechanism for metric marking. Our lab use 3 networking protocol, but to routing table are introduced only route with minimal Administrative Distance AD (say about trustworthiness appropriate routing protocol -. RIP 120, EIGRP internal route 90 and OSPF 110). Please if you will see route from intended routing protocol configure in testing environment routing protocols in this manner: 

a) RIPv 2 routing – and examine path selection – it will be with minimal hop count Branch to central

b) OSPF routing – minimal bandwidth is preferred – in our scenario are two equal path possible Branch – A – B – Central or Branch – X – Y – Central

c) EIGRP routing (cisco proprietary with maximum trustworthiness) – composite metric (default bandwidth and delay are used for calculation) will also cost load balancing between two mentioned path

Preconfigured scenario in cisco packet tracer 5.2 or above is here. Topology for testing scenario is

Output from #show ip route on Branch router with EIGRP route introduced in routing table }as mentioned earlier because this routing protocol has minimal AD 90 can be assumed as more trustworthy|.

Short look at Branch router interfaces and routing protocols config follow