Dell EMC Configuration Guide for the S3100 Series 9.14.2.4

Overview

When a router receives a packet, the router decides where to forward the packet based on the destination address in the packet, which is used to look up an entry in a routing table. However, in some cases, there may be a need to forward the packet based on other criteria: size, source, protocol type, destination, and so on. For example, a network administrator might want to forward a packet that uses transmission control protocol (TCP) across a different next-hop than packets using Internet control message protocol (ICMP). In these situations, you can a configure switch route packet according to a policy applied to interfaces.

In another scenario, when the packet comes from one source and wants to go to another destination, then route it to this next-hop or onto that specific interface. This permits routing over different links or towards different networks even while the destination is the same but depending on where the packet originates.

To enable PBR, create a redirect list. Redirect lists are defined by rules or routing policies. You can define following parameters in routing policies or rules:

• IP address of the forwarding router (next-hop IP address)
• Protocol as defined in the header
• Source IP address and mask
• Destination IP address and mask
• Source port
• Destination port
• TCP Flags

After you apply a redirect-list to an interface, all traffic passing through it is subjected to the rules defined in the redirect-list.

Traffic is forwarded based on the following:

• Next-hop addresses are verified. If the specified next hop is reachable, traffic is forwarded to the specified next-hop.
• If the specified next-hops are not reachable, the normal routing table is used to forward the traffic.
• Dell EMC Networking OS supports multiple next-hop entries in the redirect lists.
• Redirect-lists are applied at Ingress.

PBR with Redirect-to-Tunnel Option:

You can provide a tunnel ID for a redirect rule. In this case, the resolved next hop is the tunnel interface IP. The qualifiers of the rule pertain to the inner IP details. You must provide a tunnel ID for the next hop to be a tunnel interface. If you do not provide the tunnel destination IP as the next hop, the next hop is treated as an IPv4 next hop and not a tunnel next hop.

PBR with Multiple Tracking Option:

PBR with the multiple tracking option enabled extends and introduces the capabilities of object tracking to verify the next hop IP address before forwarding the traffic to the next hop. The multiple tracking options feature is most suitable for routers which have multiple devices as the next hop (primarily indirect next-hops and/or Tunnel Interfaces). These options allow you to backup Indirect next-hop with another. Choose the specific Indirect next-hop and/or Tunnel interface which is available by sending ICMP pings to verify the reach ability and/or check the Tunnel interface UP or DOWN status, and then route traffic out to that next-hop and/or Tunnel Interface