routeprotocol
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OSPF Introduction
OSPF, or Open Shortest Path First is a link state routing protocol. It is a non proprietary Interior Gateway Protocol. OSPF version 2 is defined in RFC 2328 and supports IPv4. OSPF version 3 is defined in RFC 5340 and supports IPv6 OSPF works by sending neighbouring routers link state advertisements (LSAs) that contain the…
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EIGRP Route Summarisation
To scale an EIGRP system effectively, it requires summarisation. EIGRP can summarise network prefixes on an interface basis. Prefixes contained within the summarisation are suppressed with the summary route being advertised instead, although the summary route is only advertised if a suppressed prefix is valid within the summary route. Route summarisation also creates a query…
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Mitel MiVoice 3300 Graceful Failover
To fail over phones from their primary to resilient controller before a shut down, use this maintenance command HST COURTESY HANDOFF The hand-over status can be checked with the command HST COURTESY STATUS After a reboot of the controller that handed off the phones, the phones will eventually migrate back to the original controller in…
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EIGRP Failure Detection and Timers
Hello and Hold Timers An EIGRP hello packet is not just for forming new adjacencies, but is used for checking that the neighbour is working and responsive. By default EIGRP hello packet is sent out every 5 seconds, or 60 seconds on a slow speed interface (T1 or lower) EIGRP uses a timer called a…
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EIGRP Load Balancing
Equal Cost Load Balancing EIGRP permits multiple successor routes with an equal metric to be installed into the routing table for load balancing. Installing multiple routes for the same prefix is known as equal cost multipathing, or ECMP. Unequal Cost Load Balancing EIGRP also supports unequal-cost load balancing, which permits the installation of the successor…
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EIGRP Path Metric Calculation
Before EIGRP IGRP uses multiple factors to calculate the metric for a path. Metric calculation uses bandwidth and delay by default, but can include load and reliability too. Metric = (K1 * Bandwidth + ( (K2 * Bandwidth) / (256 – Load) ) + K3 * Delay) * ( K5 / (K4 + Reliability) IGRP…
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EIGRP Neighbors
When an adjacency is formed, neighbouring EIGRP routers exchange their entire routing table, following exchanges only contain partial updates as the topology changes in the network. EIGRP uses five different types of packets to communicate with other routers, with it’s own IP number – 88. Type Packet Name Function 1 Hello Discovering EIGRP neighbour and…
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EIGRP Topology Table
In EIGRP there is a topology table that is separate from the routing table. This topology table makes EIGRP different from a traditional distance vector protocol and contains information to identify loop-free routes. Each entry in this topology table contains: The network prefix EIGRP neighbors that have advertised that network prefix The metrics from each…
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EIGRP Terminologies
Term Definition Feasible Successor A route that satisfies a feasibility condition and is kept as a backup route. The condition is that the backup route is loop free. Feasibility Condition The condition that for a route to be considered a backup route, the reported distance received must be less than the feasible distance calculated locally.…
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EIGRP Autonomous Systems
A router can run multiple EIGRP processes. Each process operates under a unique number known as a Autonomous System, or AS number. In EIGRP, only routers with the same AS number can exchange routes with each other and form neighbour relationships. If a router operates multiple EIGRP processes, a router will not transmit routes learned…