Configuring an IPv4 over IPv4 GRE tunnel

As shown in Figure 139, Group 1 and Group 2 are two private IPv4 networks. The two networks both use private network addresses and belong to the same VPN. Establish a GRE tunnel between Router A and Router B to interconnect the two private IPv4 networks Group 1 and Group 2.

Before performing the following configuration, configure an IP address for each interface, and make sure Router A and Router B can reach each other.

1. Configure Router A:

   # Create a tunnel interface Tunnel 0, and specify the tunnel mode as GRE/IPv4.

   <RouterA> system-view
   [RouterA] interface tunnel 0 mode gre
   

   # Configure an IP address for the tunnel interface.

   [RouterA-Tunnel0] ip address 10.1.2.1 255.255.255.0
   

   # Configure the source address of the tunnel interface as the IP address of GigabitEthernet 1/0/2 on Router A.

   [RouterA-Tunnel0] source 1.1.1.1
   

   # Configure the destination address of the tunnel interface as the IP address of GigabitEthernet 1/0/2 on Router B.

   [RouterA-Tunnel0] destination 2.2.2.2
   [RouterA-Tunnel0] quit
   

   # Configure a static route from Router A through the tunnel interface to Group 2.

   [RouterA] ip route-static 10.1.3.0 255.255.255.0 tunnel 0
   

2. Configure Router B:

   # Create tunnel interface Tunnel 0 and specify the tunnel mode as GRE/IPv4.

   <RouterB> system-view
   [RouterB] interface tunnel 0 mode gre
   

   # Configure an IP address for the tunnel interface.

   [RouterB-Tunnel0] ip address 10.1.2.2 255.255.255.0
   

   # Configure the source address of the tunnel interface as the IP address of interface GigabitEthernet 1/0/2 on Router B.

   [RouterB-Tunnel0] source 2.2.2.2
   

   # Configure the destination address of the tunnel interface as the IP address of the interface GigabitEthernet 1/0/2 on Router A.

   [RouterB-Tunnel0] destination 1.1.1.1
   [RouterB-Tunnel0] quit
   

   # Configure a static route from Router B through the tunnel interface to Group 1.

   [RouterB] ip route-static 10.1.1.0 255.255.255.0 tunnel 0
   

# Display tunnel interface information on Router A.

[RouterA] display interface tunnel 0
Tunnel0
Current state: UP
Line protocol state: UP
Description: Tunnel0 Interface
Bandwidth: 64kbps
Maximum Transmit Unit: 1476
Internet Address is 10.1.2.1/24 Primary
Tunnel source 1.1.1.1, destination 2.2.2.2
Tunnel keepalive disabled
Tunnel TTL 255
Tunnel protocol/transport GRE/IP
    GRE key disabled
    Checksumming of GRE packets disabled
Output queue - Urgent queuing: Size/Length/Discards 0/100/0
Output queue - Protocol queuing: Size/Length/Discards 0/500/0
Output queue - FIFO queuing: Size/Length/Discards 0/75/0
Last clearing of counters: Never
Last 300 seconds input rate: 0 bytes/sec, 0 bits/sec, 0 packets/sec
Last 300 seconds output rate: 0 bytes/sec, 0 bits/sec, 0 packets/sec
Input: 0 packets, 0 bytes, 0 drops
Output: 0 packets, 0 bytes, 0 drops

# Display tunnel interface information on Router B.

[RouterB] display interface tunnel 0
Tunnel0
Current state: UP
Line protocol state: UP
Description: Tunnel0 Interface
Bandwidth: 64kbps 
Maximum Transmit Unit: 1476
Internet Address is 10.1.2.2/24 Primary
Tunnel source 2.2.2.2, destination 1.1.1.1
Tunnel keepalive disabled
Tunnel TTL 255
Tunnel protocol/transport GRE/IP
    GRE key disabled
    Checksumming of GRE packets disabled
Output queue - Urgent queuing: Size/Length/Discards 0/100/0
Output queue - Protocol queuing: Size/Length/Discards 0/500/0
Output queue - FIFO queuing: Size/Length/Discards 0/75/0
Last clearing of counters: Never
Last 300 seconds input rate: 0 bytes/sec, 0 bits/sec, 0 packets/sec
Last 300 seconds output rate: 0 bytes/sec, 0 bits/sec, 0 packets/sec
Input: 0 packets, 0 bytes, 0 drops
Output: 0 packets, 0 bytes, 0 drops

# From Router B, ping the IP address of GigabitEthernet 1/0/1 on Router A.

[RouterB] ping -a 10.1.3.1 10.1.1.1
Ping 10.1.1.1 (10.1.1.1) from 10.1.3.1: 56 data bytes, press CTRL_C to break
56 bytes from 10.1.1.1: icmp_seq=0 ttl=255 time=11.000 ms
56 bytes from 10.1.1.1: icmp_seq=1 ttl=255 time=1.000 ms
56 bytes from 10.1.1.1: icmp_seq=2 ttl=255 time=0.000 ms
56 bytes from 10.1.1.1: icmp_seq=3 ttl=255 time=0.000 ms
56 bytes from 10.1.1.1: icmp_seq=4 ttl=255 time=0.000 ms

--- Ping statistics for 10.1.1.1 ---
5 packet(s) transmitted, 5 packet(s) received, 0.0% packet loss
round-trip min/avg/max/std-dev = 0.000/2.400/11.000/4.317 ms

The output shows that Router B can successfully ping Router A.