set ip default next-hop and set ip next-hop commands.的不同：

The set ip default next-hop command verifies the existence of the destination IP address in the routing table, and…

  • if the destination IP address      exists, the command does not policy route the packet, but forwards the      packet based on the routing table.

  • if the destination IP address      does not exist, the command policy routes the packet by sending it to the      specified next hop.

The set ip next-hop command verifies the existence of the next hop specified, and…

  • if the next hop exists in the      routing table, then the command policy routes the packet to the next hop.

  • if the next hop does not exist      in the routing table, the command uses the normal routing table to forward      the packet.

set ip default next-hop命令验证目的IP是否存在路由，并且：

1、如果目的地址有路由，那么就不对流量实施策略，而基于路由表去转发数据流量。

2、如果目的地址没有路由，那么就针对流量实施策略，将流量转发到策略指定的下一跳。

set ip next-hop 命令验证指定的下一跳是否存在，并且：

1、如果下一跳在路由表中存在，那就执行策略将流量转到下一跳。

2、如果下一跳不在路由表中存在，那就使用正常的路由表转发数据流量。

 

来自 <https://www.cisco.com/c/en/us/support/docs/ip/ip-routed-protocols/47121-pbr-cmds-ce.html#caseone>