BASIC CONFIGURATION OF ROUTER-R1::
R1(config)#int serial 1/0
R1(config-if)#ip add 1.0.0.1 255.0.0.0
R1(config-if)#no shut
R1(config-if)#exit
R1(config)#int fastethernet 0/0
R1(config-if)#ip address 200.100.50.1 255.255.255.0
R1(config-if)#no shut
R1(config-if)#exit
BASIC CONFIGURATION OF ROUTER-R2::
R2(config)#int serial 1/1
R2(config-if)#ip address 1.0.0.2 255.0.0.0
R2(config-if)#no shut
R2(config-if)#exit
R2(config)#int serial 1/0
R2(config-if)#ip address 2.0.0.1 255.0.0.0
R2(config-if)#no shut
R2(config-if)#exit
R2(config)#int fastethernet 0/0
R2(config-if)#ip address 200.100.100.1 255.255.255.0
R2(config-if)#no shut
R2(config-if)#exit
BASIC CONFIGURATION OF ROUTER-R3::
R3(config)#int serial 1/1
R3(config-if)#ip address 2.0.0.2 255.0.0.0
R3(config-if)#no shut
R3(config-if)#exit
R3(config)#interface fast 0/0
R3(config-if)#ip address 200.100.150.1 255.255.255.0
R3(config-if)#no shut
R3(config-if)#exit
ROUTING TABLE OF ROUTER-A, B, & C (Before Running EIGRP on Router-A, B & C)::
R1#show ip route
C 1.0.0.0/8 is directly connected, Serial1/0
C 200.100.50.0/24 is directly connected, FastEthernet0/0
R2#show ip route
C 1.0.0.0/8 is directly connected, Serial1/1
C 2.0.0.0/8 is directly connected, Serial1/0
C 200.100.100.0/24 is directly connected, FastEthernet0/0
R3#show ip route
C 2.0.0.0/8 is directly connected, Serial1/1
C 200.100.150.0/24 is directly connected, FastEthernet0/0
RUNNING EIGRP ON ROUTER-A::
R1(config)#router eigrp 2
R1(config-router)#network 200.100.50.0
R1(config-router)#network 1.0.0.0
R1(config-router)#end
RUNNING EIGRP ON ROUTER-B::
R2(config)#router eigrp 2
R2(config-router)#network 200.100.100.0
R2(config-router)#network 2.0.0.0
R2(config-router)#network 1.0.0.0
R2(config-router)#end
*May 17 08:02:16.387: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 2: Neighbor 1.0.0.1 (Serial1/1) is up: new adjacency
Note:: HELLO messages are used to find and maintain neighbors in the topology table. They are sent periodically and unreliably.
Router R1 sends EIGRP Hello messages to a multicast address 224.0.0.10 to find its neighbors. Router B (after receiving those messages through its interface serial 1/1) sends an acknowledgement of those messages. Router R2 also sends EIGRP Hello messages to multicast address 224.0.0.10. Only Router R1 sends an acknowledgment of EIGRP Hello messages of router R2, through network 1.0.0.0. Once Router R1 & R2 gets the acknowledgement of these EIGRP Hello messages from each other, they establishes a neighborship/adjacency and a "new adjacency" messages appears on both routers.
RUNNING EIGRP ON ROUTER-C::
R3(config)#router eigrp 2
R3(config-router)#network 200.100.150.0
R3(config-router)#network 2.0.0.0
R3(config-router)#end
*May 17 08:03:04.055: %DUAL-5-NBRCHANGE: IP-EIGRP(0) 2: Neighbor 2.0.0.1 (Serial1/1) is up: new adjacency
Note:: Now router R3 receives EIGRP Hello messages from router R2 and sends an acknowledgment. Router R3 also sends EIGRP Hello messages to multicast address 224.0.0.0 to find its neighbors. Only router B sends an acknowledgement of their EIGRP Hello messages from each other, they establishes a neighbor ship/adjacency and a "new adjacency" message appears on both routers.
NEIGHBOR TABLES OF ROUTER-R1, R2 & R3::
R1#show ip eigrp neighbors
IP-EIGRP neighbors for process 2
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
0 1.0.0.2 Se1/0 13 00:07:27 167 1002 0 9
R2#show ip eigrp neighbors
IP-EIGRP neighbors for process 2
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
1 2.0.0.2 Se1/0 10 00:07:43 250 2250 0 3
0 1.0.0.1 Se1/1 11 00:08:40 204 1224 0 3
R3#show ip eigrp neighbors
IP-EIGRP neighbors for process 2
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
0 2.0.0.1 Se1/1 1 00:08:24 132 792 0 8
Note:: On hearing HELLOS, the router creates a table of its neighbors. The continued recept of these packets maintains the neighbor table. If a HELLO from a known neighbor is not heard within a predetermined amount of time, as stated in the HOLDTIME, the router will decide that the neighbor is no longer operational and will take the appropriate action. The HOLDTIME is set at the default of three times the HELLO timer. Therefore, if the router skips three HELLOS, the neighbor is declared DEAD. The HELLO timer on a LAN is set to 5 seconds; there for the HOLDTIME is 15 seconds. On a WAN link, the HELLO timer is 60 seconds, and the HOLDTIME correspondingly is 180 seconds.
To bacome a neighbor, following conditions must be mst:
- The router must hear a Hello packet or an ACK from a neighbor.
- The Autonomous System Number (AS) in the packet header must be same as of the receiving router.
- The neighbor's metric setting must be the same.
Neighbor table displays a list of every neighbor, including the IP address, the outgoing interface, the HOLDTIME, smooth router trip timer (SRTT), and uptime or how long since the neighbor was added to the table. The table is built from information on hellos received from adjacent routers (neighbors).
Kindly note that, router R2 has two neighbors; first is router R3 located at 2.0.0.2 address and the second is router R1 located at 1.0.0.1 address. Neighbor ship/adjacency is always developed between directly connected routers.
TOPOLOGY TABLES OF ROUTER-R1, R2 & R3::
R1#show ip eigrp topology
IP-EIGRP Topology Table for AS(2)/ID(200.100.50.1)
Codes: P - Passive, A - Active, U - Update, Q - Query, R - Reply,
r - reply Status, s - sia Status
P 1.0.0.0/8, 1 successors, FD is 2169856
via Connected, Serial1/0
P 2.0.0.0/8, 1 successors, FD is 2681856
via 1.0.0.2 (2681856/2169856), Serial1/0
P 200.100.150.0/24, 1 successors, FD is 2684416
via 1.0.0.2 (2684416/2172416), Serial1/0
P 200.100.50.0/24, 1 successors, FD is 28160
via Connected, FastEthernet0/0
P 200.100.100.0/24, 1 successors, FD is 2172416
via 1.0.0.2 (2172416/28160), Serial1/0
Advertised Distance (AD):: The cost of the path to the remote network from the neighbor (the metric from the next-hop router).
Feasible Distance (FD):: The lowest-cost distance (metric) to a remote network.
R2#show ip eigrp topology
P 1.0.0.0/8, 1 successors, FD is 2169856
via Connected, Serial1/1
P 2.0.0.0/8, 1 successors, FD is 2169856
via Connected, Serial1/0
P 200.100.150.0/24, 1 successors, FD is 2172416
via 2.0.0.2 (2172416/28160), Serial1/0
P 200.100.50.0/24, 1 successors, FD is 2172416
via 1.0.0.1 (2172416/28160), Serial1/1
P 200.100.100.0/24, 1 successors, FD is 28160
via Connected, FastEthernet0/0
R3#show ip eigrp topology
P 1.0.0.0/8, 1 successors, FD is 2681856
via 2.0.0.1 (2681856/2169856), Serial1/1
P 2.0.0.0/8, 1 successors, FD is 2169856
via Connected, Serial1/1
P 200.100.150.0/24, 1 successors, FD is 28160
via Connected, FastEthernet0/0
P 200.100.50.0/24, 1 successors, FD is 2684416
via 2.0.0.1 (2684416/2172416), Serial1/1
P 200.100.100.0/24, 1 successors, FD is 2172416
via 2.0.0.1 (2172416/28160), Serial1/1
NOTE:: The topology table in EIGRP manages the selection of routes to be added to the routing table. The topology table has a record of all known network routes within the organization. The tableis built from the update packets that are exchanged by the neighbors and by replies to queries sent by the router. When the router has an understanding of the network, it runs DUAL to determine the best path to the remote network. the result is entered into the routing table.
"DUAL" (Diffusing Update Algorithm), represented with D in routing tables, is responsible for maintenance of the topology table and the creation of the routing table. The topology table records the metric as received from the advertising router, or the next logical hop. It then adds the cost of getting to that neighbor, the one that is advertising the route. The cost to the destination network from the advertising router, plus the cost to that router, equals the metric to the destination network from the router. The metric or cost from the neighbor advertising the route is known as the advertised distance (AD). The metric or cost from the router that is determining the metric or the local router is referred to as the feasible distance (FD). If the AD is less than the FD, then the next-hop router is downstream and there is no loop.
ROUTING TABLE OF ROUTER-R1, R2 & R3:: (After Running EIGRP on Router-R1, R2 & R3)
R1#show ip route
Codes: C - connected, S - static, R - RIP, M - mobile, B - BGP
D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area
N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2
E1 - OSPF external type 1, E2 - OSPF external type 2
i - IS-IS, su - IS-IS summary, L1 - IS-IS level-1, L2 - IS-IS level-2
ia - IS-IS inter area, * - candidate default, U - per-user static route
o - ODR, P - periodic downloaded static route
Gateway of last resort is not set
C 1.0.0.0/8 is directly connected, Serial1/0
D 2.0.0.0/8 [90/2681856] via 1.0.0.2, 00:39:22, Serial1/0
C 200.100.50.0/24 is directly connected, FastEthernet0/0
D 200.100.100.0/24 [90/2172416] via 1.0.0.2, 00:39:22, Serial1/0
D 200.100.150.0/24 [90/2684416] via 1.0.0.2, 00:38:25, Serial1/0
Note:: The Routing table is built from the topology table after DUAL has been run. The topology table. This is where all the routes are stored. Best paths are stored in the routing table and the router can make routing decisions.
R2#show ip route
C 1.0.0.0/8 is directly connected, Serial1/1
C 2.0.0.0/8 is directly connected, Serial1/0
D 200.100.50.0/24 [90/2172416] via 1.0.0.1, 00:41:39, Serial1/1
C 200.100.100.0/24 is directly connected, FastEthernet0/0
D 200.100.150.0/24 [90/2172416] via 2.0.0.2, 00:40:41, Serial1/0
R3#show ip route
D 1.0.0.0/8 [90/2681856] via 2.0.0.1, 00:41:18, Serial1/1
C 2.0.0.0/8 is directly connected, Serial1/1
D 200.100.50.0/24 [90/2684416] via 2.0.0.1, 00:41:18, Serial1/1
D 200.100.100.0/24 [90/2172416] via 2.0.0.1, 00:41:18, Serial1/1
C 200.100.150.0/24 is directly connected, FastEthernet0/0
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