世界蜜月圣地:IP ROUTE 0.0.0.0 0.0.0.0 VLAN 3 10.10.10.101 不但限制下一跳地址为10.10.10.101，还限定出口端口必须是vlan 3.（防止如果端口VLAN3当掉之

IP ROUTE 0.0.0.0 0.0.0.0 VLAN 3 10.10.10.101 不但限制下一跳地址为10.10.10.101，还限定出口端口必须是vlan 3.（防止如果端口VLAN3当掉之后，路由器通过其他路径到达10.10.10.101，从而可以通过10.10.10.101到达网络0.0.0.0 0.0.0.0）。

文档里还说明了ip route 0.0.0.0 0.0.0.0 Ethernet 1/2这样的命令的坏处：需借助proxy-arp, 导致高CPU利用率和很大的ARP cache 表。

Adding a static route to an Ethernet or other broadcast interface (for example, ip route 0.0.0.0 0.0.0.0 Ethernet 1/2) will cause the route to be inserted into the routing table only when the interface is up. This configuration is not generally recommended. When the next hop of a static route points to an interface, the router considers each of the hosts within the range of the route to be directly connected through that interface, and therefore it will send ARP requests to any destination addresses that route through the static route.

The practical implication of configuring "ip route 0.0.0.0 0.0.0.0 Ethernet 1/2" is that the router will consider all of the destinations that the router does not know how to reach through some other route as directly connected to Ethernet 1/2. So the router will send an ARP request for each host for which it receives packets on this network segment. This configuration can cause high processor utilization and a very large ARP cache (along with attendant memory allocation failures). Configuring a default route or other static route that directs the router to forward packets for a large range of destinations to a connected broadcast network segment can cause your router to reload.

Specifying a numerical next hop that is on a directly connected interface will prevent the router from using Proxy ARP. However, if the interface with the next hop goes down and the numerical next hop can be reached through a recursive route, you may specify both the next hop and interface (for example "ip route 0.0.0.0 0.0.0.0 Ethernet1/2 10.1.2.3") with a static route to prevent routes from passing through an unintended interface.