CCNA 3.11: Configure, verify and troubleshoot EIGRP for IPv4

Overview:

Enhanced Interior Gateway Routing Protocol (EIGRP) is a Cisco proprietary advanced distance vector dynamic routing protocol.

Study Notes:

• EIGRP uses the Diffusing Update Algorithm (DUAL)
  • Fast convergence
  • Easy on processor
  • Incremental updates
• EIGRP is an Advanced Distance vector protocol
• Combines the best of Distance Vector with Link State protocols, but is considered a Distance Vector protocol (Enhanced)
• Simple to configure
• Flexibility in summarization (not on CCNA, but good to know)
• Unequal cost load balancing
• Doesn’t age out routing entries
• No periodic updates
• 3 tables
  • Neighbor table - directly connected to the router
  • Topology table - all routes
  • Routing table - DUAL algorithm figures out best route
• Uses backup path if one exists in topology table
• Terminology
  • Feasible Distance (FD) - to reach the distant network
  • Advertise Distance (AD) - how far for neighbor to reach the network
  • Successor - primary path
  • Feasible Successor - backup path. To be considered a feasible successor, the AD must be less than the FD of the successor
  • Active Route - (bad) router is trying to find route to network
  • Passive Route - (good) router knows route to network
• Important commands to know
  • show ip route - show the routing table
  • show ip route eigrp - show only EIGRP routing table entries
  • show ip eigrp neighbors - who are the directly connected neighbors
    • H = the order in which the neighbor was discovered
    • Hold = hold time in seconds waiting for a Hello packet
    • Uptime = length of time of neighbor relationship
    • SRTT = smooth round-trip timer
    • RTO = Retransmission Time Out, time between multicasts basd on SRTT
    • Q Cnt = how many messages are in the queue
    • Seq Num = sequence number of the last update
  • show ip eigrp interfaces - shows all interfaces that EIGRP is enabled on
  • show ip eigrp topology - shows all of the FD, AD, Successor, Feasible Successor, etc.
  • show ip eigrp traffic - shows number of EIGRP packets sent and received
  • show ip protocols - displays a summary of configured routing protocol information
• EIGRP messages are sent via multicast
  • HELLO: forms the relationship
  • UPDATE: sends updates
  • QUERY: asks about routes
  • REPLY: response to a query
  • ACK: acknowledges UPDATE, QUERY and REPLY messages
• EIGRP uses triggered updates instead of the entire table
• EIGRP is its own layer 4 protocol (port 88). It doesn’t use TCP.
• EIGRP metric - used K values
  • K1 - bandwidth (statically configured value). default = 1
  • K2 - load (dynamic). default = 0
  • K3 - delay (statically configured value; in 10s of microseconds). default = 1
  • K4 - reliability (dynamic). default = 0
  • K5 - MTU (packet size). default = 0
  • EIGRP Metric Calculation (not on CCNA):

256 * [(k1 * bw) + [(k2 * bw) / (256-load)] + k3 * delay)] * [k5 / (reliability + k4)]

• For EIGRP neighbors to form, their k values must be equal
• The CCNA does not cover EIGRP authentication, filtering, manual summarization, redistribution, stub)
• Configuration:

R1#config t
    router eigrp 1 (AS number)
        network 192.168.0.0 (classful)
        no auto-summary (keeps it from summarizing)
        Ctrl+Z

R2#config t
    router eigrp 1
        network 192.168.1.0 0.0.0.3 (wildcard mask)
        Ctrl+Z


show ip protocols 
show ip route
show ip eigrp topology
show ip eigrp neighbors
show ip eigrp traffic

Labs:

PacketTracer Lab: CCNA-3.11-Configure-verify-and-troubleshoot-EIGRP-for-IPv4.pkt

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