Shulou(Shulou.com)06/01 Report--

I. Introduction to GRE

Generic Routing Encapsulation (GRE) is a lightweight tunneling protocol developed by Cisco (currently network vendors basically support GRE protocol). It is capable of encapsulating various network protocols (IP and non-IP) within tunnels. The reason why GRE is called Lightweight Tunneling Protocol is because the GRE header is small, so the encapsulation efficiency is high. However, GRE does not have any security mechanism. It is transmitted in plaintext. Tunnl IP information can be seen through packet capture. IPSec is generally used to encrypt GRE.

GRE is a typical three-layer tunneling encapsulation technology, and its packet format is as follows:

GRE packet actual format

II. GRE Basic Experimental Topology

2.1 GRE Tunnel Test Logical Topology

2.2 GRE tunnel test equipment naming and IP address assignment information

2.3 Test topology and software version description

This test uses the GNS3 IOU L3 image for testing, version i86bi-linux-l3-adventerprisek9-15.5.2T

2.4 GRE logical topology diagram

III. Basic network configuration

HQ-Route Basic Network Configuration

interface Loopback0

ip address 192.168.10.1 255.255.255.0

interface Ethernet0/0

ip address 20.20.10.10 255.255.255.0

ip route 0.0.0.0 0.0.0.0 20.20.10.1

end

ISP-Route Basic Network Configuration

interface Ethernet0/0

ip address 20.20.10.1 255.255.255.0

interface Ethernet0/1

ip address 20.20.20.1 255.255.255.0

end

BR-Route Basic Network Configuration

interface Loopback0

ip address 192.168.20.1 255.255.255.0

interface Ethernet0/1

ip address 20.20.20.10 255.255.255.0

ip route 0.0.0.0 0.0.0.0 20.20.20.1

end

IV. GRE and Dynamic Routing Configuration

After configuring the basic network, you can start configuring gre tunnel and configure ospf dynamic routing.

4.1 Configure GRE Tunnl

HQ-Route

interface Tunnel0

ip address 172.16.10.1 255.255.255.252

tunnel source 20.20.10.10

tunnel destination 20.20.20.10

BR-Route

interface Tunnel0

ip address 172.16.10.2 255.255.255.252

tunnel source 20.20.20.10

tunnel destination 20.20.10.10

4.2 configure OSPF

HQ-Route

router ospf 100

router-id 172.16.10.1

network 172.16.10.0 0.0.0.3 area 0

network 192.168.10.0 0.0.0.255 area 0

BR-Route

router ospf 100

router-id 172.16.10.2

network 172.16.10.0 0.0.0.3 area 0

network 192.168.20.0 0.0.0.255 area 0

V. GRE Tunneling and Connectivity Testing

LO0 address in BR-Route with source ping in HQ-Route

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