Traffic Forwarding Component
The traffic forwarding component imports traffic to a tunnel and forwards traffic over the tunnel. Although the information advertisement, path selection, and path establishment components are used to establish a CR-LSP in an MPLS TE tunnel, a CR-LSP (unlike an LDP LSP) cannot automatically import traffic. The traffic forwarding component must be used to import traffic to the CR-LSP before it forwards traffic based on labels.
Static Route
Static route is the simplest method for directing traffic to a CR-LSP in an MPLS TE tunnel. A TE static route works in the same way as a common static route and has a TE tunnel interface as an outbound interface.
Auto Route
An Interior Gateway Protocol (IGP) uses an auto route related to a CR-LSP in a TE tunnel that functions as a logical link to calculate a path. The tunnel interface is used as an outbound interface in the auto route. The TE tunnel is considered a P2P link with a specified metric value. The following auto routes are supported:
IGP shortcut: A route related to a CR-LSP is not advertised to neighbor nodes, preventing other nodes from using the CR-LSP.
Forwarding adjacency: A route related to a CR-LSP is advertised to neighbor nodes, allowing these nodes to use the CR-LSP.
Forwarding adjacency allows tunnel information to be advertised based on IGP neighbor relationships.
If the forwarding adjacency is used, nodes on both ends of a CR-LSP must be in the same area.
The following example demonstrates the IGP shortcut and forwarding adjacency.
- The auto route is not used. LSRE uses LSRD as the next hop in a route to LSRA and a route to LSRB; LSRG uses LSRF as the next hop in a route to LSRA and a route to LSRB.
- The auto route is used. Either IGP shortcut or forwarding adjacency can be configured:
The IGP shortcut is used to advertise the route of Tunnel 1. LSRE uses LSRD as the next hop in the route to LSRA and the route to LSRB; LSRG uses Tunnel 1 as the outbound interface in the route to LSRA and the route to LSRB. LSRG, unlike LSRE, uses Tunnel 1 in IGP path calculation.
The forwarding adjacency is used to advertise the route of Tunnel 1. LSRE uses LSRG as the next hop in the route to LSRA and the route to LSRB; LSRG uses Tunnel 1 as the outbound interface in the route to LSRA and the route to LSRB. Both LSRE and LSRG use Tunnel 1 in IGP path calculation.
Policy-based Routing
The policy-based routing (PBR) allows the system to select routes based on user-defined policies, improving security and load balancing traffic. If PBR is enabled on an MPLS network, IP packets are forwarded over specific CR-LSPs based on PBR rules.
MPLS TE PBR, the same as IP unicast PBR, is implemented based on a set of matching rules and behaviors. The rules and behaviors are defined using an apply clause, in which the outbound interface is a specific tunnel interface. If packets do not match PBR rules, they are properly forwarded using IP; if they match PBR rules, they are forwarded over specific CR-LSPs.
Tunnel Policy
- Select-seq mode: The system selects tunnels for VPN traffic in the specified tunnel selection sequence.
- Tunnel binding mode: A CR-LSP is bound to a destination address in a tunnel policy. This policy applies only to CR-LSPs.
