Cisco MPLS over GRE: Настройка и руководство по использованию (EN)

Restrictions for MPLS over GRE

Configuring MPLS over GRE Prerequisites for MPLS over GRE, on page 1 Restrictions for MPLS over GRE, on page 1 Information About MPLS over GRE, on page 2 How to Configure MPLS over GRE, on page 3 Configuration Examples for MPLS over GRE, on page 5 Additional References for MPLS over GRE, on page 8 Feature History for MPLS over GRE, on page 8 Prerequisites for MPLS over GRE Ensure that the following routing protocols are configured and working properly. • Label Distribution Protocol (LDP)—for MPLS label distribution.

• Routing protocol (ISIS or OSFP) between the core devices P1-P-P2 • MPLS between PE1-P1 and PE2-P2 • Since the ingress traffic enters the IP core from MPLS network and egress traffic leaves the IP core to enter the MPLS network, it is recommended to use QoS group value for defining QoS policies as we traverse the protocol boundary. Restrictions for MPLS over GRE • GRE Tunneling : • L2VPN over mGRE and L3VPN over mGRE is not supported. • The tunnel source can only be a loopback or a Layer 3 interface. These interfaces could either be physical interfaces or etherchannels.

• Tunnel interface supports Static Routes, Enhanced Interior Gateway Routing Protocol (EIGRP) and Open Shortest Path First (OSPF) routing protocols. • GRE Options - Sequencing, Checksum and Source Route are not supported. Configuring MPLS over GRE 1

Стр. 1

PE-to-PE Tunneling

• IPv6 generic routing encapsulation (GRE) is not supported. • Carrier Supporting Carrier (CSC) is not supported. • Tunnel source cannot be a subinterface. Information About MPLS over GRE The MPLS over GRE feature provides a mechanism for tunneling Multiprotocol Label Switching (MPLS) packets over a non-MPLS network. This feature allows you to create a generic routing encapsulation (GRE) tunnel across a non-MPLS network. The MPLS packets are encapsulated within the GRE tunnel packets, and the encapsulated packets traverse the non-MPLS network through the GRE tunnel.

When GRE tunnel packets are received at the other side of the non-MPLS network, the GRE tunnel packet header is removed and the inner MPLS packet is forwarded to its final destination. The core network between the end-points of the GRE tunnel uses ISIS or OSPF routing protocol whereas the GRE tunnel uses OSPF or EIGRP. PE-to-PE Tunneling The provider-edge-to-provider-edge (PE-to-PE) tunneling configuration provides a scalable way to connect multiple customer networks across a non-MPLS network. With this configuration, traffic that is destined to multiple customer networks is multiplexed through a single generic routing encapsulation (GRE) tunnel.

A similar nonscalable alternative is to connect each customer network through separate GRE tunnels (for example, connecting one customer network to each GRE tunnel). Note The PE device on one side of the non-MPLS network uses the routing protocols (that operate within the non-MPLS network) to learn about the PE device on the other side of the non-MPLS network. The learned routes that are established between the PE devices are then stored in the main or default routing table. The opposing PE device uses OSPF or EIGRP to learn about the routes that are associated with the customer networks that are behind the PE devices. These learned routes are not known to the non-MPLS network.

The following figure shows an end-to-end IP core from one PE device to another through the GRE tunnel that spans the non-MPLS network. Figure 1: PE-to-PE Tunneling Configuring MPLS over GRE Information About MPLS over GRE Configuring MPLS over GRE 2

Стр. 2

Configuring the MPLS over GRE Tunnel Interface

P-to-PE Tunneling The provider-to-provider-edge (P-to-PE) tunneling configuration provides a way to connect a PE device (P1) to a Multiprotocol Label Switching (MPLS) segment (PE-2) across a non-MPLS network. In this configuration, MPLS traffic that is destined to the other side of the non-MPLS network is sent through a single generic routing encapsulation (GRE) tunnel. Figure 2: P-to-PE Tunneling P-to-P Tunneling As shown in the figure below, the provider-to-provider (P-to-P) configuration provides a method of connecting two Multiprotocol Label Switching (MPLS) segments (P1 to P2) across a non-MPLS network.

In this configuration, MPLS traffic that is destined to the other side of the non-MPLS network is sent through a single generic routing encapsulation (GRE) tunnel. Figure 3: P-to-P Tunneling How to Configure MPLS over GRE The following section provides the various configuration steps for MPLS over GRE: Configuring the MPLS over GRE Tunnel Interface To configure the MPLS over GRE feature, you must create a generic routing encapsulation (GRE) tunnel to span the non-MPLS networks. You must perform the following procedure on the devices located at both ends of the GRE tunnel. Configuring MPLS over GRE P-to-PE Tunneling Configuring MPLS over GRE 3

Стр. 3

Configuring the MPLS over GRE Tunnel Interface

Procedure Configuring MPLS over GRE Configuring the MPLS over GRE Tunnel Interface Command or Action Purpose Step 1 enable Example: Device> enable Enables privileged EXEC mode. • Enter your password if prompted. Step 2 configure terminal Example: Device# configure terminal Enters global configuration mode. Step 3 interface tunnel tunnel-number Example: Device(config)# interface tunnel 1 Creates a tunnel interface and enters interface configuration mode. Step 4 ip address ip-address mask Example: Device(config-if)# ip address 10.0.0.1 255.255.255.0 Assigns an IP address to the tunnel interface. Step 5 tunnel source source-address Example:

Device(config-if)# tunnel source 10.1.1.1 Specifies the tunnel’s source IP address. Step 6 tunnel destination destination-address Example: Device(config-if)# tunnel destination 10.1.1.2 Specifies the tunnel’s destination IP address. Step 7 mpls ip Example: Device(config-if)# mpls ip Enables Multiprotocol Label Switching (MPLS) on the tunnel’s physical interface. Step 8 end Example: Device(config-if)# end Returns to privileged EXEC mode. Configuring MPLS over GRE 4

Стр. 4