Cisco CCNA GRE Tunnel Configuration

R1#ping 30.30.30.2Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 30.30.30.2, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 4/10/13 ms

Now seated at PC1 =192.168.1.1 I cannot ping PC2=192.168.2.1

PC>ping 192.168.2.1

Pinging 192.168.2.1 with 32 bytes of data:

Request timed out.

Request timed out.

Request timed out.

Request timed out.

Ping statistics for 192.168.2.1:

Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

So Goal is to have a GRE Tunnel Between R1 and R2, over internet ;and PC1 be able to Ping PC2

Step 1) Create an Int Tunnel 0 on R1 as follow

R1#

interface Tunnel0

ip address 10.10.10.1 255.255.255.252

tunnel mode gre ip

tunnel source Serial0/0/0

tunnel destination 30.30.30.2

!

As we see in above I need to use source (I use my S0/0/0 that is talking to ISP) and also I need to use the destination, which I need to use Public IP address of R2 = 30.30.30.2

R1#config t

Enter configuration commands, one per line. End with CNTL/Z.

R1(config)#int tunnel 0

R1(config-if)#

%LINK-5-CHANGED: Interface Tunnel0, changed state to up

R1(config-if)#

R1(config-if)#ip add

R1(config-if)#ip address 10.10.10.1 255.255.255.252

R1(config-if)#tun

R1(config-if)#tunnel ?

destination destination of tunnel

mode tunnel encapsulation method

source source of tunnel packets

R1(config-if)#tunnel sou

R1(config-if)#tunnel source ?

Ethernet IEEE 802.3

FastEthernet FastEthernet IEEE 802.3

GigabitEthernet GigabitEthernet IEEE 802.3z

Loopback Loopback interface

Serial Serial

R1(config-if)#tunnel source s0/0/0

R1(config-if)#

R1(config-if)#

R1(config-if)#tunne

R1(config-if)#tunnel ?

destination destination of tunnel

mode tunnel encapsulation method

source source of tunnel packets

R1(config-if)#tunnel des

R1(config-if)#tunnel destination ?

A.B.C.D ip address

R1(config-if)#tunnel destination 30.30.30.2

R1(config-if)#

%LINEPROTO-5-UPDOWN: Line protocol on Interface Tunnel0, changed state to up

R1(config-if)#tun

R1(config-if)#tunnel ?

destination destination of tunnel

mode tunnel encapsulation method

source source of tunnel packets

R1(config-if)#tunnel mo

R1(config-if)#tunnel mode ?

gre generic route encapsulation protocol

ipv6ip IPv6 over IP encapsulation

R1(config-if)#tunnel mode gr

R1(config-if)#tunnel mode gre ?

ip over IP

R1(config-if)#tunnel mode gre ip ?

<cr>

R1(config-if)#tunnel mode gre ip

Here is show run so far:

interface Tunnel0

ip address 10.10.10.1 255.255.255.252

tunnel mode gre ip

tunnel source Serial0/0/0

tunnel destination 30.30.30.2

Lets check R1# show ip int brief

R1#show ip int brief

!

Step 2) Now I will do same concept on R2 (make sure use your own interface as source and use public IP address of R1=20.20.20.1)

interface Tunnel0

ip address 10.10.10.2 255.255.255.252

mtu 1476

tunnel source Serial0/0/0

tunnel destination 20.20.20.1

R2#

R2#config t

Enter configuration commands, one per line. End with CNTL/Z.

R2(config)#int tunnel 0

R2(config-if)#

%LINK-5-CHANGED: Interface Tunnel0, changed state to up

R2(config-if)#

R2(config-if)#ip add

R2(config-if)#ip address 10.10.10.2 255.255.255.252

R2(config-if)#

R2(config-if)#tun

R2(config-if)#tunnel ?

destination destination of tunnel

mode tunnel encapsulation method

source source of tunnel packets

R2(config-if)#tunnel sou

R2(config-if)#tunnel source s0/0/0

R2(config-if)#tunnel des

R2(config-if)#tunnel destination 20.20.20.1

R2(config-if)#

%LINEPROTO-5-UPDOWN: Line protocol on Interface Tunnel0, changed state to up

R2(config-if)#trun

R2(config-if)#tun

R2(config-if)#tunnel ?

destination destination of tunnel

mode tunnel encapsulation method

source source of tunnel packets

R2(config-if)#tunnel mo

R2(config-if)#tunnel mode ?

gre generic route encapsulation protocol

ipv6ip IPv6 over IP encapsulation

R2(config-if)#tunnel mode gr

R2(config-if)#tunnel mode gre ?

ip over IP

R2(config-if)#tunnel mode gre ip ?

<cr>

R2(config-if)#tunnel mode gre ip

R2(config-if)#

Here is show run so far on R2#:

interface Tunnel0

ip address 10.10.10.2 255.255.255.252

mtu 1476

tunnel source Serial0/0/0

tunnel destination 20.20.20.1

Now Lets look at R2#show ip int brief and See if I can ping from R1 to R2 Tunnel IP address=10.10.10.2

R2#show ip int brief

R2#

R2#ping 10.10.10.2

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 10.10.10.2, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 3/11/18 ms

R2#ping 10.10.10.1

Type escape sequence to abort.

Sending 5, 100-byte ICMP Echos to 10.10.10.1, timeout is 2 seconds:

!!!!!

Success rate is 100 percent (5/5), round-trip min/avg/max = 12/17/24 ms

As we see we have connectivity from Tunnel of R1 to Tunnel of R2

But let’s see if I can ping from PC1 to PC2?

PC>ping 192.168.2.1

Pinging 192.168.2.1 with 32 bytes of data:

Request timed out.

Request timed out.

Request timed out.

Request timed out.

Ping statistics for 192.168.2.1:

Packets: Sent = 4, Received = 0, Lost = 4 (100% loss),

Not yet? Why? Since R1 routing table does not know how to get to network 192.168.2.0 ,

Let’s look at R1#show ip route

R1#show ip route

Codes: C – connected, S – static, I – IGRP, 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, E – EGP

i – IS-IS, 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 20.20.20.2 to network 0.0.0.0

10.0.0.0/30 is subnetted, 1 subnets

C 10.10.10.0 is directly connected, Tunnel0

20.0.0.0/30 is subnetted, 1 subnets

C 20.20.20.0 is directly connected, Serial0/0/0

C 192.168.1.0/24 is directly connected, FastEthernet0/0

S* 0.0.0.0/0 [1/0] via 20.20.20.2

Step 3) Make sure create a Static Route on Both R1 and R2 , to be able to see each other network ; that is R1 need to see network 192.168.2.0 and R2 need to see network 192.168.1.0

Hint: when you put the next hop, make sure use private ip address of each other =10.10.10.1 and 10.10.10.2

Let’s do R1 static route:

R1#config t

Enter configuration commands, one per line.  End with CNTL/Z.

R1(config)#ip route ?

A.B.C.D  Destination prefix

R1(config)#ip route 192.168.2.0 ?

A.B.C.D  Destination prefix mask

R1(config)#ip route 192.168.2.0 255.255.255.0 ?

A.B.C.D          Forwarding router’s address

Ethernet         IEEE 802.3

FastEthernet     FastEthernet IEEE 802.3

GigabitEthernet  GigabitEthernet IEEE 802.3z

Loopback         Loopback interface

Null             Null interface

Serial           Serial

Vlan             Catalyst Vlans

R1(config)#ip route 192.168.2.0 255.255.255.0 10.10.10.2

Here is show run on R1:

R1#show run

ip route 192.168.2.0 255.255.255.0 10.10.10.2

              (destination Net)                 (Next hop)

Here is show ip route on R1#:

R1#show ip route

Codes: C – connected, S – static, I – IGRP, 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, E – EGP

i – IS-IS, 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 20.20.20.2 to network 0.0.0.0

10.0.0.0/30 is subnetted, 1 subnets

C 10.10.10.0 is directly connected, Tunnel0

20.0.0.0/30 is subnetted, 1 subnets

C 20.20.20.0 is directly connected, Serial0/0/0

C 192.168.1.0/24 is directly connected, FastEthernet0/0

S 192.168.2.0/24 [1/0] via 10.10.10.2

S* 0.0.0.0/0 [1/0] via 20.20.20.2

R1#

Now I will do same static route on R2

R2#config t

Enter configuration commands, one per line.  End with CNTL/Z.

R2(config)#ip route ?

A.B.C.D  Destination prefix

R2(config)#ip route 192.168.1.0 ?

A.B.C.D  Destination prefix mask

R2(config)#ip route 192.168.1.0 255.255.255.0 ?

A.B.C.D          Forwarding router’s address

Ethernet         IEEE 802.3

FastEthernet     FastEthernet IEEE 802.3

GigabitEthernet  GigabitEthernet IEEE 802.3z

Loopback         Loopback interface

Null             Null interface

Serial           Serial

Vlan             Catalyst Vlans

R2(config)#ip route 192.168.1.0 255.255.255.0 10.10.10.1

R2(config)#

Here is my show run on R2#:

ip route 192.168.1.0 255.255.255.0 10.10.10.1

               (dest net )                          (Next Hop)

Now I should be able to ping from PC1 to PC2 ,

PC>ping 192.168.2.1

Pinging 192.168.2.1 with 32 bytes of data:

Reply from 192.168.2.1: bytes=32 time=5ms TTL=126

Reply from 192.168.2.1: bytes=32 time=2ms TTL=126

Reply from 192.168.2.1: bytes=32 time=2ms TTL=126

Reply from 192.168.2.1: bytes=32 time=2ms TTL=126

Ping statistics for 192.168.2.1:

Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),

Approximate round trip times in milli-seconds:

Minimum = 2ms, Maximum = 5ms, Average = 2ms

So here is summary of each router:

R1#show run

interface Tunnel0

ip address 10.10.10.1 255.255.255.252

mtu 1476

tunnel source Serial0/0/0             (use your own Interface)

tunnel destination 30.30.30.2      ( use Public IP address of R2)

!

!

interface FastEthernet0/0

ip address 192.168.1.100 255.255.255.0

duplex auto

speed auto

!

interface FastEthernet0/1

no ip address

duplex auto

speed auto

shutdown

!

interface Serial0/0/0

ip address 20.20.20.1 255.255.255.252

clock rate 2000000

!

interface Vlan1

no ip address

shutdown

!

ip classless

ip route 0.0.0.0 0.0.0.0 20.20.20.2

ip route 192.168.2.0 255.255.255.0 10.10.10.2  ( static route to other side network ; and use private IP

address of Tunnel  of R2)

Now here is Show run on R2#:

R2#

interface Tunnel0

ip address 10.10.10.2 255.255.255.252

mtu 1476

tunnel source Serial0/0/0                         (use your own interface )

tunnel destination 20.20.20.1                  ( use the public IP address of R1)

!

!

interface FastEthernet0/0

ip address 192.168.2.100 255.255.255.0

duplex auto

speed auto

!

interface FastEthernet0/1

no ip address

duplex auto

speed auto

shutdown

!

interface Serial0/0/0

ip address 30.30.30.2 255.255.255.252

clock rate 2000000

!

interface Vlan1

no ip address

shutdown

!

ip classless

ip route 0.0.0.0 0.0.0.0 30.30.30.1

ip route 192.168.1.0 255.255.255.0 10.10.10.1  (static route to other network with remote Tunnel IP Address)