What is Load Balancing

Load balancing is a standard functionality of the Cisco IOS® router software, and is available across all router platforms. It is inherent to the forwarding process in the router and is automatically activated if the routing table has multiple paths to a destination

Route Selection in Cisco Routers


The main considerations while building the routing table are:
  • Administrative distance - This is the measure of trustworthiness of the source of the route. If a router learns about a destination from more than one routing protocol, administrative distance is compared and the preference is given to the routes with lower administrative distance. In other words, it is the believability of the source of the route.

  • Metrics - This is a measure used by the routing protocol to calculate the best path to a given destination, if it learns multiple paths to the same destination. Each routing protocol uses a different metric.

  •   Prefix length -As each routing process receives updates and other information, it chooses the best path to any given destination and attempts to install this path into the routing table. For instance, if EIGRP learns of a path toward 10.1.1.0/24, and decides this particular path is the best EIGRP path to this destination, it tries to install the path it has learned into the routing table.

Static load Balancing :- Static load balancing mostly do election on AD value

AD (Administrative distance)  of  all Routing protocol



Routing protocol /Route source
Default Distance Values
Connected interface 0
Static route 1
Enhanced Interior Gateway Routing
Protocol (EIGRP) summary route		 5
External Border Gateway Protocol (eBGP) 20
Internal EIGRP 90
IGRP 100
OSPF 110
Intermediate System-to-Intermediate System (IS-IS) 115
Routing Information Protocol (RIP) 120
Exterior Gateway Protocol (EGP) 140
On Demand Routing (ODR) 160
External EIGRP 170
Internal BGP 200
Unknown 255



here we have AD value 1 for static route if router have Two route to source to destination it will elect AD value for best path and suppose on both link have same AD value so it will do load balancing.

Static load balancing lab