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5.  CONFIGURE GRE TUNNELLING USING THREE ROUTERS WITH NO

HOW TO CONFIGURE GRE TUNNELLING USING THREE ROUTERS WITH NO ROUTING IN THE MIDDLE ROUTER
 
Interface IP Address Configuration 
 
R1 
 
Interface  IP Address   Subnet Mask 
S 1/0       2.2.2.1       255.0.0.0 
E 0/0     10.1.1.1      255.0.0.0 
 
R3 
 
Interface  IP Address   Subnet Mask 
S 0         2.2.2.2        255.0.0.0 
S 1         3.3.3.1        255.0.0.0 
 
R2 
 
Interface  IP Address   Subnet Mask 
S 0/2        3.3.3.2         255.0.0.0 
Fa 0/0      20.1.1.1      255.0.0.0
 
Task  
 
Create interface tunnel 0 on R1 & R2. 
Verify connectivity. 
Configure OSPF routing protocol on R1 & R2 only. 
Verify if routes are visible in the routing table of R1 & R2. 
 
R1 
 
Ip route 3.0.0.0 255.0.0.0 2.2.2.2 
 
Int tunnel 0 
Ip address 30.1.1.1 255.0.0.0 
Tunnel source s1/0 
Tunnel destination 3.3.3.2 
Tunnel mode gre ip
 
R2 
 
Ip route 2.0.0.0 255.0.0.0 3.3.3.1 
 
Int tunnel 0 
Ip address 30.1.1.2 255.0.0.0 
Tunnel source s0/2 
Tunnel destination 2.2.2.1 
Tunnel mode gre ip 
 
Verification: 
 
R1#show ip int brief
 
The output displays tunnel 0 is up 
 
Task  
 
Configure OSPF routing protocol on R1 & R2 only. 
Verify if routes are visible in the routing table of R1 & R2. 
 
R1 
 
Router ospf 1 
Network 10.0.0.0 0.255.255.255 area 0 
Network 30.0.0.0 0.255.255.255 area 0
 
R2 
 
Router ospf 1 
Network 20.0.0.0 0.255.255.255 area 0 
Network 30.0.0.0 0.255.255.255 area 0 
 
Verification: 
 
R1#show ip ospf neighbor 
 
The output displays tunnel ip address (30.1.1.2) as the neighbor-id 
 
R1#show ip route 
 
The output displays ‘O’ (OSPF) route for network 20.0.0.0 carrying via the tunnel IP 
address (30.1.1.2) 
This indicates that routes are traveling via the gre tunnel. 
Though, there is another router in between R1 & R2, the tunnel appears as a point-to-point link. 
 
R1#traceroute 20.1.1.1
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