JUNOS Enterprise Switching

Static Routing

Although the use of static routing is often frowned upon and considered bad form, there are many practical applications for static routes, along with their aggregate/generated counterparts.

Static routing suffers from a general lack of dynamism (although Bidirectional Forwarding Detection [BFD] can mitigate this issue), which often leads to loss of connectivity or inefficient forwarding during network outages due to their static, nailed-up nature. Static routes can quickly become maintenance and administration burdens for networks that have frequent adds, moves, or changes. With that said, static routing is often used at the network edge to support attachment to stub networks, which, given their single point of entry/egress, are well suited to the simplicity of a static route.

Next Hop Types

Static routes support various next hop types, some that actually forward traffic and others that black-hole matching packets. Here are the specifics for each type of next hop:

Discard

A discard next hop results in the silent discard of matching traffic. Silent here refers to the fact that no ICMP error message is generated back to the source of the packet. You normally choose a discard next hop when the goal is to advertise a single aggregate that represents a group of prefixes, with the expectation that any traffic attracted by the aggregate route will longest-match against one of the more specific routes, and therefore will be forwarded according to the related next hop, rather than ...