Here are some final thoughts about EIGRP that are important: EIGRP does not use a transport protocol to facilitate the transfer of EIGRP messages; EIGRP runs directly above the network layer and does not use additional transport layer protocols.

Different types of load-balancing available in EIGRP: Equal Cost Path - Any routes with equal metrics are load-balanced. Thresholds are configured via the maximum-paths <#> command under the routing process, with 4 as the default and a maximum number of equal-cost paths of 32 in recent IOS releases (NX-OS supports 64 equal-cost paths).Unequal Cost Path … Continue reading 3.23 Load Balancing with EIGRP →

Unlike OSPF, you cannot directly inject default routes into EIGRP. Here are the options for configuring summarization in EIGRP. Enable auto-summary under the routing processip summary-address eigrp 100 10.0.0.0/8 (enabled on interface, where EIGRP AS is 100)redistribute static (where static 0.0.0.0/0 route is already configured)ip default-network 2.0.0.0 (where 2.0.0.0 is a classful network in a … Continue reading 3.22 EIGRP Summarization →

Summary routes reduce the size of the routing table, thereby saving precious CPU and Memory resources on a router. We also know that summary routes can limit the number of EIGRP queries on the network and improve convergence. Here is the reason: Routers that receive an EIGRP query but already have a summary route in … Continue reading 3.21 Reducing Query Scope by Using Summary Routes →

EIGRP SIA condition occurs when queries are not responded to within the 3 minute default timer. EIGRP queries use a reliable multicast communication, so a reply is necessary. Here is an example of a topology where R1 begins a query process which cascades through the network. R3 does not receive a reply from R5 within … Continue reading 3.20 Stuck in Active →

Here are some output examples of the effects of stub routing on branch router BR1A: Topology: Topology BR1A: Default EIGRP Stub Configuration (Note that router BR1A is configured to summarize 192.168.16.0/23, but the output is omitted for brevity.) HQ Output in BR1A default stub configuration. ... we change the command to eigrp stub connected summary … Continue reading 3.19 EIGRP Stub Routing →

EIGRP stub routers are typically deployed in hub-spoke topologies to provide the following benefits for scalability and optimal convergence: Improves Network Stability (less convergence; limits scope of EIGRP queries)Reduces Resource Utilization (less CPU consumption because the routing table is much smaller)Simplifies Configuration (a single, simple command) EIGRP stub routing is configured under the routing process … Continue reading 3.18 EIGRP Stub Routers →

Note the following troubleshooting commands useful in investigating EIGRP query activity. When queries are being sent by a router, its show ip eigrp topology output will show the destination as Active (A). Here are the conditions for sending EIGRP queries: Queries are sent when a route is lost and there is no Feasible Successor in … Continue reading 3.17 EIGRP Queries →

A final important note about path calculation in EIGRP... The feasibility condition is the relationship between a Reported Distance and the Feasible Distance. In other words, if a given path has a Reported Distance that is greater that the Successor path cost (Feasible Distance), it does not become a Feasible Successor. That does not necessarily … Continue reading 3.16 EIGRP Path Calculation Example →

A few key terms to remember about the Feasibility Condition, the mechanism by which EIGRP maintains a loop-free topology. Path Cost (Feasible Distance) - The total cost along the path from a source to a destination from the local router's perspective. This is the sum of the Reported Distance plus the path cost of the … Continue reading 3.15 Feasibility Condition →