Policy-Based Routing Guidelines and Limitations

DE.

Policy-based routing (PBR) is a feature that allows the network administrator to define and apply policies for traffic forwarding based on certain criteria such as source address, protocol type, or packet size. PBR is commonly used to implement advanced routing policies and provide traffic engineering capabilities in the network. However, there are certain guidelines and limitations that should be considered when using PBR:

A. A policy-based routing map can have multiple match or set statements per route-map statement. This guideline is true. A route-map is a logical structure used to define the sequence of match and set statements that define a policy for traffic forwarding. A route-map statement can include multiple match or set statements to specify multiple conditions or actions to be applied to a packet. For example, a route-map statement can match on both the source and destination IP addresses and set the next-hop address and QoS markings.

B. A match command can refer to more than one ACL in a route map used for policy-based routing. This guideline is also true. An Access Control List (ACL) is a set of rules used to filter or classify packets based on their attributes such as source and destination IP addresses, protocol type, and port numbers. In PBR, an ACL can be used as a match criterion in a route-map statement to selectively apply the policy to the packets that match the specified criteria. A route-map statement can reference multiple ACLs to define more complex matching criteria.

C. Policy-based routing and WCCPv2 are not supported on the same interface if bank chaining is disabled. This guideline is true. Web Cache Communication Protocol version 2 (WCCPv2) is a protocol used to redirect web traffic to a cache server for content filtering and caching. In some cases, PBR and WCCPv2 may be used together to implement more advanced traffic control policies. However, if WCCPv2 bank chaining is disabled, PBR and WCCPv2 cannot be used on the same interface because they both rely on the same packet marking mechanism (IP Precedence or DSCP) to select the traffic to be redirected.

D. An ACL used in a policy-based routing route map cannot include a deny statement. This guideline is false. An ACL used in a route-map statement for PBR can include both permit and deny statements to define the matching criteria. The permit statement specifies the packets that should be forwarded according to the policy, while the deny statement specifies the packets that should be dropped or forwarded according to the normal routing table.

E. The same route map can be shared among different interfaces for policy-based routing as long as the interfaces belong to the same VRF instance. This guideline is also true. A Virtual Routing and Forwarding (VRF) instance is a mechanism used to create multiple virtual routing tables in a single physical device, allowing different customers or applications to share the same network infrastructure while maintaining their own routing domains. A route-map statement can be associated with a VRF instance and used to apply the same policy to multiple interfaces that belong to the same VRF. This allows for efficient policy deployment and management.