EIGRP 1 Part 1

EIGRP; Enhance Interior Gateway Protocol is a Cisco Propriety protocol and can only be used between Cisco devices which is a downfall as it is one of the fastest protocols when it comes to convergence due to the way it works. EIGRP has something called successor route and feasible successor route. It pretty much remembers the alternative path in-case the (Primary) success route is removed from the routing table. Even though the (secondary) path by have a worse metric, it still keeps it in the topology table. EIGRP uses well known multicast address 224.0.0.10(IPV4) and ff02::a(IPV6) to communicate with its neighbors. EIGRP only advertises its full routing table when it first establishes a neighborship. The rest of the updates are triggered updates (when a network change occurs)


Router(config)#int f0/0
Router(config-if)#no shut
Router(config-if)#ip address 192.168.1.1 255.255.255.0
Router(config)#router eigrp 10
Router(config)#no auto-summary (disables auto summary for classes addresses)
Router(config-router)#passive-interface default  (Enable passive interface for all interfaces on this device for eigrp process 10)
Router(config-router)#no passive-interface fastEthernet 0/0  (Exclude interface f0/0 from being a passive interface, hellos can be sent now)
Router(config-router)#network 192.168.1.1 0.0.0.0 
Router(config-router)#exit

This is how your verify which interfaces are in passive mode.

Router#show ip protocols
Routing Protocol is "eigrp 10"
  Outgoing update filter list for all interfaces is not set
  Incoming update filter list for all interfaces is not set
  Default networks flagged in outgoing updates
  Default networks accepted from incoming updates
  EIGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0
  EIGRP maximum hopcount 100
  EIGRP maximum metric variance 1
  Redistributing: eigrp 10
  EIGRP NSF-aware route hold timer is 240s
  Automatic network summarization is in effect
  Maximum path: 4
  Routing for Networks:
    192.168.1.1/32
  Passive Interface(s):
    FastEthernet0/0
    FastEthernet0/1
    VoIP-Null0
  Routing Information Sources:
    Gateway         Distance      Last Update
  Distance: internal 90 external 170

Verify Eigrp hello timer. The default is 5 seconds. 3 to 1 ratio on the hold time.

Router#show ip eigrp interfaces detail fastEthernet 0/0
IP-EIGRP interfaces for process 10
                        Xmit Queue   Mean   Pacing Time   Multicast    Pending
Interface        Peers  Un/Reliable  SRTT   Un/Reliable   Flow Timer   Routes
Fa0/0              1        0/0        45       0/2           50           0
  Hello interval is 5 sec
  Next xmit serial <none>
  Un/reliable mcasts: 0/1  Un/reliable ucasts: 1/3
  Mcast exceptions: 1  CR packets: 1  ACKs suppressed: 0
  Retransmissions sent: 0  Out-of-sequence rcvd: 0
  Authentication mode is not set
  Use multicast
Router#

Verify EIGRP hold time. The default is 15seconds  There is no way if knowing what is configured unless your issue a show run which is not always allowed on the ccnp exams so you need to guesstimate but this should be fairly simple.

Router#show ip eigrp neighbors
IP-EIGRP neighbors for process 10
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq
                                            (sec)         (ms)       Cnt Num
0   192.168.1.2             Fa0/0             11 00:02:14   45   270  0  3
Router#show ip eigrp neighbors
IP-EIGRP neighbors for process 10
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq
                                            (sec)         (ms)       Cnt Num
0   192.168.1.2             Fa0/0             13 00:02:18   45   270  0  3
Router#show ip eigrp neighbors
IP-EIGRP neighbors for process 10
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq
                                            (sec)         (ms)       Cnt Num
0   192.168.1.2             Fa0/0             12 00:02:19   45   270  0  3
Router#show ip eigrp neighbors
IP-EIGRP neighbors for process 10
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq
                                            (sec)         (ms)       Cnt Num
0   192.168.1.2             Fa0/0             11 00:02:19   45   270  0  3
Router#show ip eigrp neighbors
IP-EIGRP neighbors for process 10
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq
                                            (sec)         (ms)       Cnt Num
0   192.168.1.2             Fa0/0             10 00:02:20   45   270  0  3
Router#show ip eigrp neighbors
IP-EIGRP neighbors for process 10
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq
                                            (sec)         (ms)       Cnt Num
0   192.168.1.2             Fa0/0             10 00:02:25   45   270  0  3
Router#show ip eigrp neighbors
IP-EIGRP neighbors for process 10
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq
                                            (sec)         (ms)       Cnt Num
0   192.168.1.2             Fa0/0             13 00:02:27   45   270  0  3
Router#show ip eigrp neighbors
IP-EIGRP neighbors for process 10
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq
                                            (sec)         (ms)       Cnt Num
0   192.168.1.2             Fa0/0             12 00:02:28   45   270  0  3
Router#

Updating Hello and Hold Timer. You can not do this on a per neighbor case, all neighbors known through this interface will have to abide by these settings. Think if your using a switch with one core vlan.

3 to 1 ratio recommended. This tells your neighbor device that he needs to send you a hello before 6 seconnds and this also tells your router to send a hello every 2 seconds.

Router(config-if)#ip hello-interval eigrp 10 2
Router(config-if)#ip hold-time eigrp 10 6