Public IP Route Recursion to an SR Tunnel

Public BGP Route Recursion to an SR Tunnel

When users access the Internet, if IP forwarding is implemented for packets, core devices between the users and the Internet are forced to learn a large number of Internet routes. This puts huge strain on the core devices and negatively impacts their performance. To solve this problem, non-labeled public BGP or static route recursion to an SR tunnel can be configured on the user access device, so that packets can be forwarded over the SR tunnel when users access the Internet, preventing problems induced by insufficient performance, heavy load, and service processing on core devices.

On the network shown in Figure 1, public BGP route recursion to an SR LSP can be achieved through the following process:

An IGP and SR are deployed on each PE and P in E2E mode, and an SR LSP is established.
A BGP peer relationship is established between the PEs for them to learn the routes of each other.
The BGP route recurses to the SR LSP on PE1.

Figure 1 Public BGP route recursion to an SR LSP
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On the network shown in Figure 2, public BGP route recursion to an SR-MPLS TE tunnel can be achieved through the following process:

An IGP and SR are deployed on each PE and P in E2E mode, and an SR-MPLS TE tunnel is established.
A BGP peer relationship is established between the PEs for them to learn the routes of each other.
A tunnel policy is configured on the PEs so that the BGP route recurses to the SR-MPLS TE tunnel on PE1.

Figure 2 Public BGP route recursion to an SR-MPLS TE tunnel

Static Route Recursion to an SR Tunnel

If the next hop of a static route cannot be directly reached, route recursion is required. If such a route recurses to an SR tunnel, packets transmitted over the route can then be forwarded based on labels.

On the network shown in Figure 3, static route recursion to an SR LSP can be achieved through the following process:

An IGP and SR are deployed on each PE and P in E2E mode, and an SR LSP destined for PE2's loopback interface address is established on PE1.
A static route is configured on PE1, and PE2's loopback interface address is specified as the next hop of the route.
After receiving an IP packet, PE1 encapsulates a label into the packet and forwards the packet over the SR LSP.

Figure 3 Static route recursion to an SR LSP
Click to enlarge

On the network shown in Figure 4, static route recursion to an SR-MPLS TE tunnel can be achieved through the following process:

An IGP and SR are deployed on each PE and P in E2E mode, and an SR-MPLS TE tunnel destined for PE2's loopback interface address is established on PE1.
A static route is configured on PE1, and PE2's loopback interface address is specified as the next hop of the route.
A tunnel policy is configured on the PEs so that the static route recurses to the SR-MPLS TE tunnel. After receiving an IP packet, PE1 encapsulates labels into the packet and forwards the packet over the SR-MPLS TE tunnel.

Figure 4 Static route recursion to an SR-MPLS TE tunnel