EIGRP

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Distance Vector + Link State (distance vector = split horizon)

Features

• Transport - IP; protocol type 88
• Metric - bandwidth; delay (in 1/10 microseconds); load; reliability; mtu
• Hello Interval
• Hold Timer - when neighbor router has failed
• Update Destination Address - 224.0.0.10; retransmissions are unicast
• Full & Partial Updates - full updates on neighbor discovery; rest are partial
• Authentication - md5
• VLSM/Classless
• Route Tags
• Next-hop-field
• Manual Route Summarization
• Multi Protocol - IP; IPX; AppleTalk

Neighbors

• Pass authentication
• Same AS number
• Source IP of hello needs to be in subnet of primary IP
• K values need to match

Updates

• Reliable Transport Protocol (RTP) to send multicast
• Waits for unicast EIGRP Acks
• Resends to non-ack'd neighbors - Retransmission Timeout (RTO)

Tables

• Topology - state info regarding neighbors
  • Metric = 256(10,000,000/bandwidth) + 256(delay)
  • # show ip eigrp topology
    • "via 172.16.1.1 (x/y), serial 0/0.4"
      • x = calculated metric
      • y = RD = 256(delay)
    • Feasible Distance (FD) - best FD is successor route (gets added to routing table)

Convergence

• Reported Distance (RD) - metric of route report by neighbors
• Feasible Distance (FD) - value of lowest metric path to subnet
• Feasibility Condition - multiple routes to subnet; RD < FD
• Successor Route - lowest metric to destination prefix
• Feasible Successor (FS) - not successor; meets feasibility condition; used when successor route fails
• Input Event - occurrence that can change topology table
• Local Computation - reaction to input events; leading to the use of a FS

Local Computation

• Scenarios

  • if FS route exists, install lowest metric FS in routing table; send updates
  • if no FS exist, query neighbors
    • called "going active" on a route
      • multicasts query messages
      • waits for all to respond (rcvreply debug message)
      • if neighbor router has no FS, it will also send a Query to remaining neighbors
        • response to original query is withheld until all responses to it's own query are received
    • if process never completes, considered stuck-in-active

• Stuck-in-active

  • Active Timer
  • Brings down neighbors that didn't reply
    • config-router# timers active-time disable

• Limiting Query Scope

  • Route Summarization - will reply that it doesnt have a FS even if a specific route matches a summary
  • Stub Routers - neighbors wont send queries to stubs

Stubs

• Types

  • Connected - advertise conected routes; on interfaces in network command
  • Summary - advertise auto-summarized and static summary routes
  • Static - advertise static routes; assuming "redistribute static" command
  • Redistributed - is redistribution is enabled
  • Receive-only - do not advertise

config-router# eigrp stub connected summary

Loading Balancing

Variance - any FS route < (variance * FD) is added to the routing table

config-router# variance <multiplier>
config-router# maximum-paths 1...6 (default 4)
config-router# traffic-share balanced (more packets to lower metrics)
config-router# traffic-share min (send traffic to lowest metric)
config-router# traffic-share min across-interfaces (different outgoing interface is chosen)
config-router# no traffic-share (balances evenly; ignores eigrp metrics)

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Authentication

config-if# ip authentication mode eigrp <asn> md5
config-if# ip authentication key-chain eigrp <asn> <key-name>

Route Filtering

config-router# distribute-list <acl> in FastEthernet0/0

config# ip prefix-list WORD seq 10 permit 0.0.0.0/0 le 32
confg-router# distribute-list prefix WORD in FastEthernet0/0

Weight/Metric Configuration

config-router# metric weights 0 1 0 1 0 0 (type of service, bandwidth, load, delay, reliability, mtu)

Redistribute Specific Networks

config# route-map WORD
config-route-map# match ip address 3 (ACL 3)
config# router eigrp 500
config-router# redistribute rip metric 1500 0 255 1 1500 WORD

Timers

config-if# ip hello-interval 1 2
config-if# ip hold-time 1 6

Bandwidth Percent

config-if# ip bandwidth-percent eigrp <asn> 150 (out of 255)

Passive Interface

config-router# passive-interface Ethernet0/0 (stops hello messages)

Redistribute Internal and External Specifically

config# interface s0/0.1
config-subif# no split-horizon eigrp 500
config-router# redistribute ospf 1 match [internal | external] metric 3000 0 255 1 1500
config# router ospf 1
config-router# redistribute eigrp 500 subnets metric 500000

Summary Configuration

config-router# no auto-summary
config# interface s0/0.1
config-if# ip summary-address 500 155.155.0.0 255.255.0.0

View and Debug Commands

show ip eigrp neighbor
debug eigrp packet hello
debug eigrp packet update ack
debug eigrp fms (finite state machine; FD and FS logic)