4.3 Configure, verify, and troubleshoot GRE tunnel connectivity

Screenshot_2018-03-17_21-57-45.png

To configure a GRE tunnel (modify accordingly):

!
interface Tunnel0
 ip address 192.168.0.1 255.255.255.0
 tunnel source Ethernet0/0
 tunnel destination 1.0.0.2
!
interface Ethernet0/0
 ip address 1.0.0.1 255.255.255.0
!
router ospf 1
 network 192.168.0.0 0.0.0.255 area 0
!

To verify a GRE tunnel:

Router#show ip int bri
Interface IP-Address OK? Method Status Protocol
Ethernet0/0 1.0.0.2 YES manual up up 
Ethernet0/1 unassigned YES unset administratively down down 
Ethernet0/2 unassigned YES unset administratively down down 
Ethernet0/3 unassigned YES unset administratively down down 
Serial1/0 unassigned YES unset administratively down down 
Serial1/1 unassigned YES unset administratively down down 
Serial1/2 unassigned YES unset administratively down down 
Serial1/3 unassigned YES unset administratively down down 
Tunnel0 192.168.0.2 YES manual up up 
Router#show int tunnel 0
Tunnel0 is up, line protocol is up 
 Hardware is Tunnel
 Internet address is 192.168.0.2/24
 MTU 17916 bytes, BW 100 Kbit/sec, DLY 50000 usec, 
 reliability 255/255, txload 1/255, rxload 1/255
 Encapsulation TUNNEL, loopback not set
 Keepalive not set
 Tunnel linestate evaluation up
 Tunnel source 1.0.0.2 (Ethernet0/0), destination 1.0.0.1
 Tunnel Subblocks:
 src-track:
 Tunnel0 source tracking subblock associated with Ethernet0/0
 Set of tunnels with source Ethernet0/0, 1 member (includes iterators), on interface 
 Tunnel protocol/transport GRE/IP
 Key disabled, sequencing disabled
 Checksumming of packets disabled
 Tunnel TTL 255, Fast tunneling enabled
 Tunnel transport MTU 1476 bytes
 Tunnel transmit bandwidth 8000 (kbps)
 Tunnel receive bandwidth 8000 (kbps)
 Last input 00:00:09, output 00:00:09, output hang never
 Last clearing of "show interface" counters 00:02:40
 Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
 Queueing strategy: fifo
 Output queue: 0/0 (size/max)
 5 minute input rate 0 bits/sec, 0 packets/sec
 5 minute output rate 0 bits/sec, 0 packets/sec
 13 packets input, 1296 bytes, 0 no buffer
 Received 0 broadcasts (0 IP multicasts)
 0 runts, 0 giants, 0 throttles 
 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
 16 packets output, 1636 bytes, 0 underruns
 0 output errors, 0 collisions, 0 interface resets
 0 unknown protocol drops
 0 output buffer failures, 0 output buffers swapped out
Router#show ip route 192.168.0.0
Routing entry for 192.168.0.0/24, 2 known subnets
 Attached (2 connections)
 Variably subnetted with 2 masks
C 192.168.0.0/24 is directly connected, Tunnel0
L 192.168.0.2/32 is directly connected, Tunnel0
Router#show ip ospf neighbor

Neighbor ID Pri State Dead Time Address Interface
192.168.0.1 0 FULL/ - 00:00:31 192.168.0.1 Tunnel0

 

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