Policy Based Routing

Explanation

Normal policy based routing (PBR) is used to route packets that pass through the device. Packets that are generated by the router (itself) are not normally policy-routed. To control these packets, local PBR should be used. For example: Router(config)# ip local policy route-map map-tag (compared with normal PBR: Router(config-if)# ip policy route-map map-tag)

Reference: http://www.cisco.com/c/en/us/td/docs/ios/12_2/qos/configuration/guide/fqos_c/qcfpbr.html

Question 2

Explanation

The set command specifies the action(s) to take on the packets that match the criteria. You can specify any or all of the following:

* precedence: Sets precedence value in the IP header. You can specify either the precedence number or name.
* df: Sets the “Don’t Fragment” (DF) bit in the ip header.
* vrf: Sets the VPN Routing and Forwarding (VRF) instance.
* next-hop: Sets next hop to which to route the packet.
* next-hop recursive: Sets next hop to which to route the packet if the hop is to a router which is not adjacent.
* interface: Sets output interface for the packet.
* default next-hop: Sets next hop to which to route the packet if there is no explicit route for this destination.
* default interface: Sets output interface for the packet if there is no explicit route for this destination.

(Reference: http://www.cisco.com/en/US/docs/ios/12_2/qos/configuration/guide/qcfpbr_ps1835_TSD_Products_Configuration_Guide_Chapter.html)

Question 3

Explanation

The “show route-map “route-map name” displays the policy routing match counts so we can learn if PBR reacts to packets sourced from 172.16.0.0/16 or not.

Question 4

Explanation

First we should check the access-list log, if the hit count does not increase then no packets are matched the access-list -> the policy based routing match counts will not increase.