Chapter 2 Cisco version 6 Static Routing

2.2.1.5 The difference between an Ethernet multi-access network and a point-to-point serial network is

that a point-to-point serial network has only one other device on that network, the router at the other end of the link. With Ethernet networks, there may be many different devices sharing the same multi-access network, including hosts and even multiple routers. By only designating the Ethernet exit interface in the static route, the router will not have sufficient information to determine which device is the next-hop device, hence the necessity of using a fully-specified route, only if CEF is not enabled.

2.2.1.2 Fully specified static route

The next-hop IP address and exit interface are specified

2.1.2.3 Default static routes are used:

When no other routes in the routing table match the packet destination IP address. In other words, when a more specific match does not exist. A common use is when connecting a company's edge router to the ISP network. When a router has only one other router to which it is connected. In this situation, the router is known as a stub router.

2.1.2.3 Configuring a default static route creates

a Gateway of Last Resort.

2.2.1.4 Configuring a directly connected static route with an exit interface

allows the routing table to resolve the exit interface in a single search, instead of two searches.

2.1.2.6 Default Static Routes

are commonly used with edge routers to connect to the ISP network.

2.1.2.5 Floating static routes

are static routes that are used to provide a backup path to a primary static or dynamic route, in the event of a link failure.

2.1.2.6 Floating Static Route

backs up a route already discovered by a dynamic routing protocol.

2.1.2.3 A default route

can be dynamically learned or statically configured.

2.2.1.1. The following parameters are required to configure static routing:

network-address - Destination network address of the remote network to be added to the routing table, often this is referred to as the prefix. subnet-mask - Subnet mask, or just mask, of the remote network to be added to the routing table. The subnet mask can be modified to summarize a group of networks. One or both of the following parameters must also be used: ip-address - The IP address of the connecting router to use to forward the packet to the remote destination network. Commonly referred to as the next hop. exit-intf - The outgoing interface to use to forward the packet to the next hop. The distance parameter is used to create a floating static route by setting an administrative distance that is higher than a dynamically learned route.

2.1.1.1 Unlike a dynamic routing protocol,

static routes are not automatically updated and must be manually reconfigured any time the network topology changes.

2.2.1.4 Although the routing table entry indicates "directly connected",

the administrative distance of the static route is still 1. Only a directly connected interface can have an administrative distance of 0.

2.2.1.3 Next-hop routes cause

the router to do a recursive lookup, which consumes resources.

2.1.2.5 Floating static routes

use a slightly higher administrative distance than Enhanced Interior Gateway Protocol, so in the event of EIGRP failing the floating static route can be used by the router.

2.1.2.6 Standard Static Routes are

useful when connecting to stub networks

2.2.1.4 For point-to-point interfaces,

you can use static routes that point to the exit interface or to the next-hop address.

2.1.1.2 Disadvantages of Static Routing:

Initial configuration and maintenance is time-consuming. Configuration is error-prone, especially in large networks. Administrator intervention is required to maintain changing route information. Does not scale well with growing networks; maintenance becomes cumbersome. Requires complete knowledge of the whole network for proper implementation.

2.1.1.1 A router can learn about remote networks in one of two ways:

Manually - Remote networks are manually entered into the route table using static routes. Dynamically - Remote routes are automatically learned using a dynamic routing protocol.

2.2.1.2 Next-hop route

Only the next-hop IP address is specified

2.2.1.2 Directly connected static route

Only the router exit interface is specified

2.1.1.3 Static routing has three primary uses:

Providing ease of routing table maintenance in smaller networks that are not expected to grow significantly. Routing to and from stub networks. A stub network is a network accessed by a single route, and the router has only one neighbor. Using a single default route to represent a path to any network that does not have a more specific match with another route in the routing table. Default routes are used to send traffic to any destination beyond the next upstream router.

2.1.1.2 Advantages of Static Routing:

Static routes are not advertised over the network, resulting in better security. Static routes use less bandwidth than dynamic routing protocols, no CPU cycles are used to calculate and communicate routes. The path a static route uses to send data is known.

2.1.2.4 To reduce the number of routing table entries, multiple static routes can be summarized into a single static route if:

The destination networks are contiguous and can be summarized into a single network address. The multiple static routes all use the same exit interface or next-hop IP address.

2.2.1.1 ip route Command Syntax

ip route network-address subnet-mask {ip-address | exit-intf} distance (optional)

2.1.2.3 A default static route

is simply a static route with 0.0.0.0/0 as the destination IPv4 address.

2.2.1.4 For multipoint/broadcast interfaces,

it is more suitable to use static routes that point to a next-hop address.

2.1.2.6 Default Static Routes

matches all packets and sends them to a specific default gateway.