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Chapter 2 Static Routes (Configure Static and Default Routes (Configure IP…

- - - - A router can learn about remote networks in one of two ways:
        
        Dynamically - Remote routes are automatically learned using a dynamic routing protocol.
        
        Manually - Remote networks are manually entered into the route table using static routes.
    - - Static routing provides some advantages over dynamic routing, including:
        
        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.
      - Static routing has the following disadvantages:
        
        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.
    - - 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.
  - - - Routes are to connect to a specific remote network.
    - - is a route that matches all packets and is used by the router if a packet does not match any other, more specific route in the routing table.
    - - 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.
    - - The floating static route is only used when the primary route (static or dynamic) is not available.
        
        To accomplish this, the floating static route is configured with a higher administrative distance than the primary route.
        
        If a link fails and the route disappears from the routing table, the router selects the floating static route as the best path to reach a network
- - - - Static routes are configured using the ip route global configuration command.
        
        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 | prefix length - 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
    - - The next hop can be identified by an IP address, exit interface, or both. How the destination is specified creates one of the three following route types:
        
        Next-hop route - Only the next-hop IP address is specified
        
        Directly connected static route - Only the router exit interface is specified
        
        Fully specified static route - The next-hop IP address and exit interface are specified
        
        In a recursive static route, only the next hop is specified. The output interface is derived from the next hop. This example shows such a definition:
        ipv6 route 2001:DB8::/32 2001:DB8:3000:1
      - with the use of the CEF forwarding mechanism, static routes with an exit interface are considered unnecessary. A single lookup is performed using a combination of the FIB and adjacency table stored in the data plane.
    - - show ip route | show ipv6 route
      - show ip route static | show ipv6 route static
      - show ip route network | show ipv6 route network
  - - - There are three ways a host route can be added to the routing table:
        
        Automatically installed when an IP address is configured on the router
        
        Configured as a static host route
        
        Host route automatically obtained through other methods (discussed in later courses)
  - - - Static routes are marked with “S” in the output of the routing table.
      - For IPv6 static routes, the next-hop address can be the link-local address of the adjacent router. However, you must specify an interface type and an interface number when using a link-local address as the next hop,
- - - - Common IOS troubleshooting commands include:
        
        ping
        
        ping 192.168.2.1 source g0/0 (this use the LN interface of R1 as the source)
        
        traceroute
        
        show ip route
        
        show ip interface brief
        
        show cdp neighbors detail