EIGRP-running routers connect by exchanging information to form what is known as an adjacency relationship, whether using serial or Ethernet interfaces.
This information includes route details such as metric, total delay, and reported distance. Additionally, this data shows the interface bandwidth statement value – a configurable static parameter expressed in Kilobits per Second. As a result of using weighted formula to allocate resources more efficiently.
EIGRP is a routing protocol
EIGRP is an advanced distance vector routing protocol specifically tailored for large networks. Utilizing a multi-neighbor relationship model to calculate and distribute routes, this distance vector routing protocol does not broadcast its full routing table every time something changes; rather it only sends out changes as route changes arise – this reduces network traffic significantly while simultaneously offering quick convergence times and using minimal bandwidth resources.
EIGRP can also load balance across unequal cost links by adding multiple routes of equal cost to its routing table, and using them for routing decisions either per packet or destination. Depending on which switch is being used, EIGRP may either load balance across multiple switches simultaneously or utilize only one for its routing needs.
The routing table contains all possible paths to reach any given destination and is maintained by EIGRP as information exchanged among neighbors is exchanged. Routers send Hello packets that indicate their neighbor status to all their peers in their network; when new neighbors join they are added into this table.
Once a router has an extensive routing table, it can select the optimal path to each destination. Typically, the path with the lowest metric value is selected as its successor route and then advertised to its neighbors.
Calculation of metrics relies on five so-called K values, configured on every router and used to establish its routing metric. By default, bandwidth and delay are considered; these variables can be changed with different weight values to alter its appearance. It also takes into account interface bandwidth (not actual line bandwidth).
EIGRP relies on multicast to transmit update, query and reply packets that contain the latest routing table updates as part of its synchronization process. Packets are regularly sent out and must be acknowledged – to monitor this activity run the command show ip eigrp topology on any router in question.
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It is designed to be easy to configure
EIGRP, or Enhanced Interior Gateway Routing Protocol, is an advanced Cisco routing protocol designed to be easy to configure. Using incremental and triggered routing updates to enhance router operation while decreasing network traffic levels. Furthermore, this advanced protocol features unequal cost load balancing as well as using metrics such as bandwidth, delay, and link reliability to identify short routes across networks.
Static routes work, but their limitations don’t scale with networks as they expand and troubleshooting them is difficult. Dynamic routing protocols offer much better solutions; Cisco’s own Enhanced Interior Gateway Routing Protocol (EIGRP) is easily configurable and works in both small and large networks alike.
EIGRP is a distance vector routing protocol that uses neighbor relationships to distribute routing information across networks. A router becomes part of an EIGRP network by seeing hello packets sent from another router on it; once accepted into its neighborhood it will regularly send hello packets as part of keeping its routing table up to date.
The router then stores the route information it collects from its neighbors in two tables: topology and neighbor. The former stores details about a route’s total delay and feasible distance; its successor table stores IP addresses of routers that have direct physical connections to it; its successor table lists IP addresses that have possible successors without creating loops.
EIGRP uses routing tables to store routing information, but also computes an overall metric that other routers use to compare their paths towards their destinations. The overall metric is defined by (reported distance + advertised distance)/2; this metric serves as the main determinant when neighbor routers establish adjacencies with each other. To make EIGRP backward compatible with IGRP, its overall metric is increased by multiplying it by 256; in this way IGRP and EIGRP share the same basic formula when computing their overall metrics.
It uses unequal cost load balancing
Unequal Cost Load Balancing (UCLB) is a feature of EIGRP which distributes network traffic over multiple paths to improve performance and reliability by decreasing data transmitted over one path at once and decreasing congestion through evenly spreading out loads across available paths. Furthermore, this feature can enhance network resiliency by redirecting traffic if one of primary paths fail – an added layer of protection against failure that ensures traffic continues as normal despite possible disruptions to primary paths.
UCLB utilizes routing metrics to select routes for installation in its routing table, with these being determined by minimum bandwidth and maximum delay configurations on each router interface. This differs from traditional routing protocols which use bandwidth/delay values as distance-calculating factors between networks.
EIGRP, developed by Cisco and other networking equipment vendors to meet a need for a scalable routing protocol that could connect many home office teleworker connections to corporate intranets, is used by Cisco and many other networking equipment vendors today.
As its network expanded, Cisco realized it must route traffic through multiple paths to prevent bottlenecks and maximize resource use. To address this challenge, Cisco developed EIGRP as a new routing protocol using equal cost path load balancing combined with intelligent load balancing to distribute network traffic evenly over various paths.
To enable unequal-cost path load balancing, configure the EiGRP unbalanced-path command on any router responsible for sending traffic towards specific destinations. If the unbalanced-path configuration does not function as expected, try altering its ip prefix or resetting its configuration; either may help.
Routers configured with UCLB may advertise routes to networks with higher metrics than others to that same network, which could cause routing loops if they lead to the same destination via multiple paths. EIGRP routers offer the ability to disable split horizon by applying distribution lists on serial interfaces – this may help avoid such issues.
It is compatible with IPv4 and IPv6
EIGRP scales well and offers fast convergence times with low resource utilization. EIGRP’s use of routing tables reduces network traffic by only transmitting updates to routers on the shortest paths to their destinations, thus decreasing network resource impact caused by routing protocol updates. Furthermore, unequal cost path load balancing helps balance traffic across multiple paths.
IPv6 EIGRP is similar to its IPv4 counterpart in many ways, yet there are some key distinctions. For instance, EIGRP in IPv6 cannot use classful routing protocols to learn routes from other routers within its domain and does not support classful aggregates due to IPv6’s lack of classful networks. Instead, EIGRP supports link state aggregation which makes resolving routing issues simpler than ever.
To configure EIGRP for IPv6, first enable it on all router interfaces; on Cisco routers this can be achieved using “ipv6 router eigrp 1” or “network ipv6 eigrp”. Once activated, EIGRP will exchange routing information with neighboring routers to establish neighbor relationships and then publish routes it has learned on all its interfaces.
Once EIGRP is installed and enabled, its configuration must be verified. To do this, issue the show ipv6 route eigrp command on each router in your network to make sure FE80::x is being used as the unicast routing protocol and that PCs in the network can ping each other; additionally, verify end-to-end connectivity exists between PCs in your network.
One way of verifying EIGRP for IPv6 is to set up loopbacks on all routers, which will be advertised into the EIGRP topology and demonstrate its working properly. You can also use R5’s show ipv6 protocols command to confirm G0/0 is configured as its passive interface default, and each router’s show ipv6 routes command to confirm all interfaces are participating in EIGRP processes.
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