On this post, I will be showing how to built a basic GRE tunnel that is running over EIGRP.
Topology:
Configurations:
MANILA#sh run | sec eigrp
router eigrp 123
network 192.168.12.0
Singapore#sh run | sec eigrp
router eigrp 123
network 192.168.12.0
network 192.168.23.0
Melbourne#sh run | sec eigrp
router eigrp 123
network 192.168.23.0
Checking the EIGRP Neighbors,
MANILA#show ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(123)
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
0 192.168.12.2 Se3/0 11 00:14:41 144 864 0 5
Singapore#show ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(123)
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
1 192.168.12.1 Se3/0 12 00:14:57 222 1332 0 3
0 192.168.23.3 Se3/1 12 00:16:19 118 708 0 3
Melbourne#show ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(123)
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
0 192.168.23.2 Se3/1 13 00:15:37 98 588 0 3
Checking the routes on Manila and Melbourne,
MANILA#show ip route eigrp 123
!
Gateway of last resort is not set
D 192.168.23.0/24 [90/2681856] via 192.168.12.2, 00:17:12, Serial3/0
MANILA#
Melbourne#show ip route eigrp 123
!
Gateway of last resort is not set
D 192.168.12.0/24 [90/2681856] via 192.168.23.2, 00:17:45, Serial3/1
Melbourne#
Creating the Tunnel Interface:
MANILA# sh run | sec Tunnel
interface Tunnel0
ip address 192.168.13.1 255.255.255.0
tunnel source 192.168.12.1
tunnel destination 192.168.23.3
Melbourne#sh run | sec Tunnel
interface Tunnel0
ip address 192.168.13.3 255.255.255.0
tunnel source 192.168.23.3
tunnel destination 192.168.12.1
Configured EIGRP AS 13 to pass the traffic 172.16.10.0/24 and 172.16.30.0/24 networks through the GRE Tunnel.
MANILA#sh run | sec eigrp
router eigrp 13
network 172.16.10.0 0.0.0.255
network 192.168.13.0
Melbourne#sh run | sec eigrp
router eigrp 13
network 172.16.30.0 0.0.0.255
network 192.168.13.0
Melbourne#
Checking the EIGRP neighbors between Manila and Melbourne.
MANILA#sh ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(123)
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
0 192.168.12.2 Se3/0 14 00:23:00 144 864 0 5
EIGRP-IPv4 Neighbors for AS(13)
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
0 192.168.13.3 Tu0 12 00:14:00 167 1470 0 3
MANILA#
Melbourne#show ip eigrp neighbors
EIGRP-IPv4 Neighbors for AS(123)
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
0 192.168.23.2 Se3/1 14 00:23:35 98 588 0 3
EIGRP-IPv4 Neighbors for AS(13)
H Address Interface Hold Uptime SRTT RTO Q Seq
(sec) (ms) Cnt Num
0 192.168.13.1 Tu0 13 00:13:13 183 1470 0 3
Melbourne#
Checking the routing table.
MANILA#show ip route eigrp
!
Gateway of last resort is not set
172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
D 172.16.30.0/24 [90/27008000] via 192.168.13.3, 00:14:27, Tunnel0
D 192.168.23.0/24 [90/2681856] via 192.168.12.2, 00:23:28, Serial3/0
MANILA#
Melbourne#show ip route eigrp
!
Gateway of last resort is not set
172.16.0.0/16 is variably subnetted, 3 subnets, 2 masks
D 172.16.10.0/24 [90/27008000] via 192.168.13.1, 00:15:09, Tunnel0
D 192.168.12.0/24 [90/2681856] via 192.168.23.2, 00:24:10, Serial3/1
Melbourne#
Testing the reachability:
MANILA#ping 172.16.30.3 source 172.16.10.1
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.16.30.3, timeout is 2 seconds:
Packet sent with a source address of 172.16.10.1
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 100/114/132 ms
MANILA#
******************End of Laboratory*********************************************
NETWORK LESSON 
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