3.4.2.4 Packet Tracer – Configuring GRE

Last Updated on January 28, 2021 by Admin

3.4.2.4 Packet Tracer – Configuring GRE

Packet Tracer – Configuring GRE (Answer Version)

Answer Note: Red font color or Gray highlights indicate text that appears in the Answer copy only.

Topology

Addressing Table

Device	Interface	IP Address	Subnet Mask	Default Gateway
RA	G0/0	192.168.1.1	255.255.255.0	N/A
	S0/0/0	64.103.211.2	255.255.255.252	N/A
	Tunnel 0	10.10.10.1	255.255.255.252	N/A
RB	G0/0	192.168.2.1	255.255.255.0	N/A
	S0/0/0	209.165.122.2	255.255.255.252	N/A
	Tunnel 0	10.10.10.2	255.255.255.252	N/A
PC-A	NIC	192.168.1.2	255.255.255.0	192.168.1.1
PC-C	NIC	192.168.2.2	255.255.255.0	192.168.2.1

Objectives

Part 1: Verify Router Connectivity

Part 2: Configure GRE Tunnels

Part 3: Verify PC Connectivity

Scenario

You are the network administrator for a company which wants to set up a GRE tunnel to a remote office. Both networks are locally configured, and need only the tunnel configured.

Part 1: Verify Router Connectivity

Step 1: Ping RA from RB.

1. Use the show ip interface brief command on RA to determine the IP address of the S0/0/0 port.
2. From RB ping the IP S0/0/0 address of RA.

Step 2: Ping PCA from PCB.

Attempt to ping the IP address of PCA from PCB. We will repeat this test after configuring the GRE tunnel. What were the ping results? Why? The pings failed because there is no route to the destination.

Part 2: Configure GRE Tunnels

Step 1: Configure the Tunnel 0 interface of RA.

1. Enter into the configuration mode for RA Tunnel 0.
   • RA(config)# interface tunnel 0
2. Set the IP address as indicated in the Addressing Table.
   • RA(config-if)# ip address 10.10.10.1 255.255.255.252
3. Set the source and destination for the endpoints of Tunnel 0.
   • RA(config-if)# tunnel source s0/0/0
   • RA(config-if)# tunnel destination 209.165.122.2
4. Configure Tunnel 0 to convey IP traffic over GRE.
   • RA(config-if)# tunnel mode gre ip
5. The Tunnel 0 interface should already be active. In the event that it is not, treat it like any other interface.
   • RA(config-if)# no shutdown

Step 2: Configure the Tunnel 0 interface of RB.

Repeat Steps 1a – e with RB. Be sure to change the IP addressing as appropriate.

RB(config)# interface tunnel 0
RB(config-if)# ip address 10.10.10.2 255.255.255.252
RB(config-if)# tunnel source s0/0/0
RB(config-if)# tunnel destination 64.103.211.2
RB(config-if)# tunnel mode gre ip
RB(config-if)# no shutdown

Step 3: Configure a route for private IP traffic.

Establish a route between the 192.168.X.X networks using the 10.10.10.0/30 network as the destination.

RA(config)# ip route 192.168.2.0 255.255.255.0 10.10.10.2
RB(config)# ip route 192.168.1.0 255.255.255.0 10.10.10.1

Part 3: Verify Router Connectivity

Step 1: Ping PCA from PCB.

Attempt to ping the IP address of PCA from PCB. The ping should be successful.

Step 2: Trace the path from PCA to PCB.

Attempt to trace the path from PCA to PCB. Note the lack of public IP addresses in the output.

Device Configs

Router RA

no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
hostname RA
license udi pid CISCO2911/K9 sn FTX15242579
spanning-tree mode pvst
interface Tunnel0
ip address 10.10.10.1 255.255.255.252
tunnel source Serial0/0/0
tunnel destination 209.165.122.2
tunnel mode gre ip
interface GigabitEthernet0/0
ip address 192.168.1.1 255.255.255.0
duplex auto
speed auto
interface GigabitEthernet0/1
no ip address
duplex auto
speed auto
shutdown
interface GigabitEthernet0/2
no ip address
duplex auto
speed auto
shutdown
interface Serial0/0/0
ip address 64.103.211.2 255.255.255.252
interface Serial0/0/1
no ip address
shutdown
interface Vlan1
no ip address
shutdown
ip classless
ip route 192.168.2.0 255.255.255.0 10.10.10.2
ip route 0.0.0.0 0.0.0.0 Serial0/0/0
line con 0
line aux 0
line vty 0 4
login
end

 

Router RB

 

no service timestamps log datetime msec
no service timestamps debug datetime msec
no service password-encryption
license udi pid CISCO2911/K9 sn FTX152497Z4
spanning-tree mode pvst
interface Tunnel0
ip address 10.10.10.2 255.255.255.252
tunnel source Serial0/0/0
tunnel destination 64.103.211.2
tunnel mode gre ip
interface GigabitEthernet0/0
ip address 192.168.2.1 255.255.255.0
duplex auto
speed auto
interface GigabitEthernet0/1
no ip address
duplex auto
speed auto
shutdown
interface GigabitEthernet0/2
no ip address
duplex auto
speed auto
shutdown
!
interface Serial0/0/0
ip address 209.165.122.2 255.255.255.252
!
interface Serial0/0/1
no ip address
shutdown
interface Vlan1
no ip address
shutdown
ip classless
ip route 192.168.1.0 255.255.255.0 10.10.10.1
ip route 0.0.0.0 0.0.0.0 Serial0/0/0
line con 0
line aux 0
line vty 0 4
login
end