Routing policy decision sequence

General information

Routing policy statements and routing policy statement entries are compared against incoming packets in the following sequence.

1. The routing packets arrive.

2. The first routing policy is analyzed.

3. The first entry in the routing policy statement is analyzed. Entries are compared in sequence based on the Entry ID, from lowest to highest.

   If a match is found based on the first routing policy statement entry, the specified action is performed. You can use the Action parameter to specify the continued evaluation of route policy entries, or additional policy statements.

4. If no match is found, the packet is compared against the second routing policy statement entry. If a match is found based on the second routing policy statement entry, the specified action is performed.

5. If no match is found, the packet is compared sequentially against all remaining routing policy statements and routing policy statement entries. If a match is found, the specified action is performed.

6. If the packet does not match any routing policy statements or entries, the default action is performed.

   The following figure shows how routes are analyzed using routing policies.

Figure 54-1: Routing policy analysis workflow

No action/default action routing policy decision sequence

When no action or default action in a routing policy is matched on a packet, then the routing protocols determine the default action for the packet. The action can be specified for the protocol. If the action is not specified, there are default routing protocol import and export actions performed, as described in the following table.

Table 54-5: Default routing protocol actions

Protocol	Default import route action	Default export route options
BGP	All routes from BGP peers are accepted and forwarded to the BGP route selection process.	All active internal BGP routes are advertised to BGP peers. All non-BGP learned routes are not advertised to BGP peers.
IS-IS	IS-IS route acceptance cannot be configured. All IS-IS routes are accepted from IS-IS neighbors.	All internal IS-IS routes are advertised to all IS-IS neighbors. All non-IS-IS learned routes are not advertised to IS-IS neighbors.
OSPF	OSPF route acceptance cannot be configured. All OSPF routes are accepted from OSPF neighbors.	All OSPF routes are advertised to all OSPF neighbors. All non-OSPF learned routes are not advertised to OSPF neighbors.
RIP	All RIP-learned routes are accepted from RIP peers.	All non-RIP learned routes are not advertised to RIP peers.