Contents
- Select. Network. …
- Add. a tunnel and enter the tunnel. …
- On the. Config. …
- Assign the tunnel interface to a. Virtual System. …
- Assign the tunnel interface to a. Security Zone. …
- Assign an IP address to the tunnel interface. ( …
- Click.
Generic Routing Encapsulation (GRE) is a tunneling protocol developed by Cisco that allows the encapsulation of a wide variety of network layer protocols inside point-to-point links. A GRE tunnel is used when packets need to be sent from one network to another over the Internet or an insecure network.
What does GRE tunneling mean? Encapsulating packets within other packets is called “tunneling.” GRE tunnels are usually configured between two routers, with each router acting like one end of the tunnel. The routers are set up to send and receive GRE packets directly to each other.
A GRE tunnel functions like a VPN but without the encryption; it transports packets from one endpoint to another through the public network. GRE tunnels typically use keepalive packets to determine if a tunnel is up.
GRE does add an additional 24-byte header of overhead. This overhead contains a new 20-byte IP header, which indicates the source and destination IP addresses of the GRE tunnel. The remaining 4 bytes are the GRE header itself. Additional GRE options can increase the GRE header by up to another 12 bytes.
- show ip interface.
- show ip route.
- show ip interface tunnel.
- show ip tunnel traffic.
- show interface tunnel.
- show statistics tunnel.
Generic routing encapsulation (GRE) provides a private path for transporting packets through an otherwise public network by encapsulating (or tunneling) the packets. GRE tunneling is accomplished through tunnel endpoints that encapsulate or de-encapsulate traffic.
GRE tunneling with the Key field allows the operators to have home networks that consist of multiple Virtual Private Networks (VPNs), which may have overlapping home addresses. When the tuple
| PARAMETER | GRE | IPSec |
|---|---|---|
| Standard | GRE is defined in RFC 2784 standard | IPSEC ESP is defined in RFC2406 |
Generic routing encapsulation (GRE) tunnels are not secure because Generic routing encapsulation (GRE) does not encrypt its Data payload. In real-time, Generic routing encapsulation (GRE) used together with other secure tunnelling protocols like IPSec to provide network security.
Generic Routing Encapsulation (GRE) is a protocol that encapsulates packets in order to route other protocols over IP networks. GRE is defined by RFC 2784. GRE was developed as a tunneling tool meant to carry any OSI Layer 3 protocol over an IP network.
GRE (IP protocol 47) is neither TCP (IP protocol 6) nor UDP (IP protocol 17). GRE does not contain any mechanism for reliability check like TCP (which guarantee that data will come valid and in order, or not at all) or UDP (which guarantee that data will come valid or not at all).
What are three features of a GRE tunnel? Creates non-secure tunnels between remote sites. Transports multiple Layer 3 protocols. Creates additional packet overhead.
Point-to-Point Tunneling Protocol (PPTP) uses TCP port 1723 and IP protocol 47 Generic Routing Encapsulation (GRE).
GRE was developed as a tunneling tool meant to carry any OSI Layer 3 protocol over an IP network. In essence, GRE creates a private point-to-point connection like that of a virtual private network (VPN).