Static Routing

Static routes

Two ways a router learns about remote networks

Static routes are not automatically updated and must be reconfigured

What happens to static routes when the topology changes

Automatically

Dynamic routing adapts to topology changes

Administrator intervention

Static routing requires this when topology changes

Simple and complex topologies

Dynamic routing is suitable for

Simple topologies

Static routing is suitable for

CPU, memory, link bandwidth

Dynamic routing uses these resources

Smaller networks not expected to grow;

routing to and from stub networks;

a single default route

Three uses for static routes

Stub network

A network accessed by a single route and has one neighbor

Default route

Route that represents a path to any network not found in the routing table

Standard static route

Static route used to connect to a specific network

Default static route

Static route that matches all packets when no specific route matches

0.0.0.0/0

Destination IPv4 address used by a default static route

A Gateway of Last Resort

What a default static route creates

Summary static route

Static route that summarizes multiple static routes into one network address

Floating static route

Static route used to provide a backup path

1

Default administrative distance of a static route

90

EIGRP administrative distance

110

OSPF administrative distance

120

RIP administrative distance

ip route

Command used to configure an IPv4 static route

ip route network-address subnet-mask {ip-address | exit-intf}

Basic IPv4 static route syntax

network-address

Parameter representing the destination network

ip-address

Parameter commonly referring to the next-hop router's IP address

exit-intf

Parameter used to specify the outgoing interface

Next-hop IP address; router exit interface; next-hop IP address and exit interface

Three ways a next hop can be identified

Next-hop static route

Static route where only the next-hop IP address is specified

Recursive lookup

Process requiring two routing table lookups for a next-hop static route

Directly connected static route

Static route where only the router exit interface is specified

Fully specified static route

Static route where both next-hop IP address and exit interface are specified

Cisco Express Forwarding (CEF)

Cisco forwarding technology that provides optimized lookup

Forwarding Information Base (FIB) and adjacency table

Two tables used by CEF

Recursive lookup

What CEF eliminates for next-hop IP address lookups

show ip route static

Command that displays only static routes

S

Routing table code that indicates a static route

*

Symbol indicating a candidate default route

None of the bits are required to match

Meaning of /0 in a default route entry

ipv6 unicast-routing

Command that enables a router to forward IPv6 packets

ipv6 route

IPv6 static route command

Next-hop static IPv6 route; directly connected static IPv6 route; fully specified static IPv6 route

Three IPv6 static route types

::/0

IPv6 default static route destination

32-bit mask

IPv4 host route mask length

128-bit mask

IPv6 host route mask length

L

Routing table symbol for a local route

ping

Command used to test connectivity

traceroute

Command used to trace the path through the network

show ip route

Command used to examine the IPv4 routing table

show ip interface brief

Command used to verify interface status

show cdp neighbors detail

Command used to view neighboring Cisco devices in detail

Incorrect static route

Common problem shown when a traceroute loops between routers