Filter Based Forwarding (FBF) / Policy Based Routing (PBR) on XRE (EX-8200 VC) with routing-instance type ‘forwarding’

Filter Based Forwarding (FBF) / Policy Based Routing (PBR) on XRE (EX-8200 VC) with routing-instance type ‘forwarding’

When a router receives a packet, it normally decides where to forward it based on the destination address in the packet, which is then used to look up an entry in a routing table. However, in certain cases, there may be a need to forward the packet based on other criteria.

For example, a network administrator might want to forward a packet based on the source address. This permits routing of packets originating from different sources to different networks, even when the destinations are the same and can be useful when interconnecting several private networks.

To achieve filter based forwarding (FBF) or Cisco Policy Based Routing (PBR) with RVIs on EX8200 VC.

Note:

  • FBF for the forwarding routing-instance type is supported on 8200-VC, with RVI interface only (the next-hop must be reachable through RVI interface) using current Junos. It is not supported, if the next-hop is reachable through an L3 interface. Support for L3 interface may be introduced with certain 12.x JUNOS releases.
  • When ingress and egress ports are on different member swicthes and the packet is routed from the default routing-instance to another forwarding instance type, then the VLAN ID gets modified in such a way that the traffic is redirected to the default routing-instance for subsequent routing. This issue is addressed in PR721436 and has been fixed in Junos 11.2R5, 11.3R5, 11.4R2, and 12.1R1 or later.

filter-based-forwarding-fbf-policy-based-routing-pbr-xre-ex-8200-vc-routing-instance-type-forwarding

Here the next-hop is reachable in the sify_424 routing-instance from RVI vlan.4.

Resolved route 116.1.1/24 is successfully installed on the PFE.

If the L3 physical interface is used, instead of RVI, the route does not resolve on PFE and FBF support will not work.
Delete the RVI vlan.4 and assigned IP to ge-5/0/19.

Now next-hop is reachable from ge-5/0/19.

But PFE has a hold route for 116.1.1/24, as use of L3 IFL is not supported on 8200-VC.

 

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James Palmer

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