EIGRP

Giriş
EIGRP'yi öğrenirken şu kavramları bilmek gerekir.

Successor = Best Route
Feasible Successor = Next Best Route

EIGRP Tabloları
EIGRP iki tablo kullanır.

EIGRP has two tables: neighbors, and topology.

Topology Tablosu
Açıklaması şöyle.

EIGRP neighbors exchange data from the EIGRP topology table.

Routing Tablosu
Açıklaması şöyle.

The routing table contains routes learned from different sources -- EIGRP, other routing protocols such as OSPF and BGP, static, and connected routes. To include these other information sources, you need to redistribute the other source into EIGRP.

Açıklaması şöyle.

In the case of EIGRP, as you may know the DUAL algorithm actually makes final metric determination (and thus routing decisions) based on several values known as K1-K5. These are actually various multipliers of values that the protocol is carrying. The values themselves are (minimum path) bandwidth, (additive) link delay, (minimum) link reliability and (maximum) link utilization. Again, though, these K values are integer multipliers of these values, not the values themselves. What's more, by default three of these five values are actually left at zero while the other two are left at 1. The net effect here is that link reliability and link utilization are ignored, while link bandwidth and delay are actually used. Why these attributes? Because they are statically defined on links. In early deployments utilizing all of these values it was quickly discovered that the variability of these values could cause rippling instability in larger networks. What's worse, utilization in particular created an oscillation condition, where traffic would tend to be steered away from a busy link only to cause another set of links to become busy which would, in turn, redirect back to the original link. The issue here is that the network is potentially never in a completely settled/predictable state. This basically means that a busy link can actually commonly lead to network instability - which means that slowness for one set of users just resulted in unpredictable performance for potentially a great many users. Similarly, link quality determination tended to magnify a circuit taking a few CRC errors into a network-wide convergence event. At a minimum this churned CPU, but worst-case it could (and did) yield outages unto itself.

maximum paths
Açıklaması şöyle

maximum-paths (EIGRP)

To control the maximum number of parallel routes that the Enhanced Interior Gateway Routing Protocol (EIGRP) can support, use the maximum-paths command in the appropriate configuration mode. To remove the maximum-paths command from the configuration file and restore the system to its default condition with respect to the routing protocol, use the no form of this command.

maximum-paths maximum

no maximum-paths

Şöyle yaparız.

router eigrp 1
 maximum-paths 1

Feasible Successor Nedir ?
Şu iki kavramı bilmek gerekir.

Feasible Distance = Next best route için belirtilen değer
Reported Distance = O an raporlanan değer.

Açıklaması şöyle

If the Reported Distance for a route is less than or equal to the Feasible Distance, then the route is a Feasible Successor. You can have multiple Feasible Successors, or none at all. The Feasible Distance is the historic, since the route went Active, best metric for a destination. It is possible for there to be multiple routes to the destination, but none are Feasible Successors because the Reported Distances are all larger than the Feasible Distance.

If the Successor route goes away, then the Feasible Successor with the best metric takes over, end of story. If there are no Feasible Successors (because none of the other routes' Reported Distances meet the Feasible Distance), then a query goes out to see if there are any neighbors that know how to reach the destination. If so, then the new Successor, and possibly Feasible Successors, are chosen.

Açıklaması şöyle

A route is entered into the EIGRP topology table as a feasible successor only if it meets the feasibility condition, which asserts that the reported distance of a route must be lower than the feasible distance of the current successor route.

Succesorları Görmek
Şöyle yaparız. Burada biri hızlı bir yavaş olan iki komşu var. 192.168.14.17 hızlı olan

Switch1#show ip eigrp topology  192.168.1.0
EIGRP-IPv4 Topology Entry for AS(100)/ID(192.168.14.18) for 192.168.1.0/24
  State is Passive, Query origin flag is 1, 1 Successor(s), FD is 3072
  Descriptor Blocks:
  192.168.14.17 (GigabitEthernet1/0/10), from 192.168.14.17, Send flag is 0x0
      Composite metric is (3072/2816), route is Internal
      Vector metric:
        Minimum bandwidth is 1000000 Kbit
        Total delay is 20 microseconds
        Reliability is 255/255
        Load is 1/255
        Minimum MTU is 1500
        Hop count is 1
        Originating router is 192.168.14.10
  192.168.14.2 (GigabitEthernet2/0/13), from 192.168.14.2, Send flag is 0x0
      Composite metric is (28416/2816), route is Internal
      Vector metric:
        Minimum bandwidth is 100000 Kbit
        Total delay is 110 microseconds
        Reliability is 255/255
        Load is 1/255
        Minimum MTU is 1500
        Hop count is 1
        Originating router is 192.168.14.10