Friday, May 21, 2010


Advertised Distance = Metric reported FROM a neighbor, alos known as 'Reported Distance'
Feasible Distance = The metric of the best path
Successor = Best/Primary path assed in to the routing table
Feasible Successor = Secondary/backup path retained in the topology table, must meet the 'Feasibility Condition'
Feasibility Condition = To be considered a Feasible Successor, the Advertised Distance MUST be lower than the Feasible Distance (full path) to be considered a Feasible Successor
- If the Advertised Distance is larger than the Feasible Distance then by definition the path must longer and therefore not as good.
- The Feasible Successor means that a new path can be selected with out recalculation therefore the protocol is fast

CCNP - ENTERPRISE - EIGRP configuration review

Configure EIGRP:
R1(config)#router eigrp 1
R1(config-router)#no auto-summary
Where 1 = The EIGRP AS number which must match with adjacency neighbors
           no auto-summary = prevents route summarisation and advertises subnets
            Network = states which network to advertise AND which interface to advertise it out of

Verify EIGRP:
#sh ip eigrp neighbors
    -displays status of neighbor relationships

#sh ip eigrp topology
    - displays the topology of the eigrp AS
Where - P=Passive, network is available and installed in the routing table
    A = Active, network is currently unavailable and EIGRP is working to source a new route
    U = Update, network is being updated
    Q = Query, applied if an outstanding packet query exists for the network i.e. waiting for an ACK
    R = Reply, router is generating a reply for this network or waiting on an ACK to a reply packet
    SIA = Stuck-In-Active, signifies EIGRP convergence issue.
    *SIA status must be reset when one or more queries to a neighbor do not return before the Active timer expires (usually 3 minutes)