Why is it advisable to enter a next hop

Term of the Day. Best of Techopedia weekly. News and Special Offers occasional. Next Hop. Techopedia Explains Next Hop. What Does Next Hop Mean? Techopedia Explains Next Hop The Internet consists of thousands of different networks of every size and shape.

Synonyms Next Optimal Router. Figure 2 illustrates the issue. For each block, the network, broadcast, and gateway addresses are not available for server IP addressing, which results in three IP addresses being used inefficiently. In addition, the blocks consume unused IP addresses for future expansion. This issue can be resolved by configuring the interface on the router with an address from the reserved IPv4 prefix for shared address space RFC and by using static routes pointed at interfaces.

The shared address space address range is The interface in the router gets allocated an IP address from the RFC space, so it is not consuming publicly routable address space, and connectivity is handled with static routes on an interface. The interface in the server is configured with a publicly routable address, but the router interfaces are not.

Network and broadcast addresses are consumed out of the RFC space rather than the publicly routable address space. Figure 3 shows the efficient use of IP address space. In this configuration, each customer gets allocated individual IP addresses per server. There is a static route that can be configured as a host route. The interface in the router gets allocated an IP address from the RFC space, so it does not consume publicly routable address space, and connectivity is handled with static routes out to an interface.

With this configuration, no publicly routable IP addresses are wasted. This example shows a single host route per server, which is a mapping. This could equate to a large number of static host routes, if maintained. For scaling purposes, we need to support nonhost routes in this environment. If Customer C were allocated server IPs from You can control the importation of static routes into the routing and forwarding tables in a number of ways.

Primary ways include assigning one or more of the following attributes to the route:. By default, static routes are not retained in the forwarding table when the routing process shuts down. When the routing process starts up again, any routes configured as static routes must be added to the forwarding table again.

To avoid this latency, routes can be flagged as retain , so that they are kept in the forwarding table even after the routing process shuts down.

Retention ensures that the routes are always in the forwarding table, even immediately after a system reboot. Static routes are eligible for readvertisement by other routing protocols by default. In a stub area where you might not want to readvertise these static routes under any circumstances, you can flag the static routes as no-readvertise. Generally, only active routes are included in the routing and forwarding tables.

If a static route's next-hop address is unreachable, the route is marked passive , and it is not included in the routing or forwarding tables. To force a route to be included in the routing tables regardless of next-hop reachability, you can flag the route as passive.

If a route is flagged passive and its next-hop address is unreachable, the route is included in the routing table, and all traffic destined for the route is rejected.

This example shows how to prevent a static route from being readvertised into OSPF, thereby preventing the route from appearing in the routing and forwarding tables. You always keep the static route in the routing table as long as you have a route to the next hop.

In this problem scenario, you might expect that since the primary link is down, you should have the floating static route with administrative distance installed in the routing table on R1. However, the floating static route is not installed in the routing table since the regular static route remains in the routing table. The next hop address Configure a static route on R1 where the next hop cannot be recursive to another static route.

Cisco recommends that you configure both the outbound interface and the next hop address for a static route. In the case of a serial interface, the specification of the outbound interface is sufficient because a serial interface is a point-to-point interface. If the outbound interface is an Ethernet interface, then you must configure both the outbound interface and the next hop address.

Cisco highly recommends that you specify the outbound interface and the next hop IP address when you configure static routes. When the outbound interface is a point-to-point type of link for example, a serial link , the specification of the next hop address is not needed. Skip to content Skip to search Skip to footer. Available Languages. Download Options. Updated: June 4, Contents Introduction. Introduction This document describes the basic concept of static routes. Background Information Static routes are used for a variety of reasons and are often used when there is no dynamic route to the destination IP address, or when you want to override the dynamically learned route.

Asked 10 years, 9 months ago. Active 9 years, 11 months ago. Viewed 4k times. A static route can either be created by specifying the next hop What is the best practice in this situation? Improve this question. I agree with joeqwerty's answer; there really isn't a best practice here, the use of a next hop address vs. One minor point; it's actually possible to specify both a next hop IP address and an outgoing interface. Such a static route will only be valid if the outgoing interface is up and a route to the next hop exists via that interface.

Add a comment. Active Oldest Votes. Improve this answer. Vlad H Vlad H 3 3 bronze badges. So to make sure I understand. If I use the interface the router will send an ARP for every packet which would be really bad if it's the gateway of last resort.

This is partially mitigated with ip cef and completely eliminated when using the next hop ip address?