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Configuring Static Routing
This chapter describes how to configure static routing on the switch.
This chapter includes the following sections:
• Information About Static Routing, page 10-1
• Licensing Requirements for Static Routing, page 10-3
• Prerequisites for Static Routing, page 10-3
• Guidelines and Limitations, page 10-3
• Default Settings, page 10-4
• Configuring Static Routing, page 10-4
• Verifying the Static Routing Configuration, page 10-6
• Configuration Examples for Static Routing, page 10-6
• Additional References, page 10-7
Information About Static Routing
Routers forward packets using either route information from route table entries that you manually
configure or the route information that is calculated using dynamic routing algorithms.
Static routes, which define explicit paths between two routers, cannot be automatically updated; you
must manually reconfigure static routes when network changes occur. Static routes use less bandwidth
than dynamic routes. No CPU cycles are used to calculate and analyze routing updates.
You can supplement dynamic routes with static routes where appropriate. You can redistribute static
routes into dynamic routing algorithms but you cannot redistribute routing information calculated by
dynamic routing algorithms into the static routing table.
You should use static routes in environments where network traffic is predictable and where the network
design is simple. You should not use static routes in large, constantly changing networks because static
routes cannot react to network changes. Most networks use dynamic routes to communicate between
routers but may have one or two static routes configured for special cases. Static routes are also useful
for specifying a gateway of last resort (a default router to which all unroutable packets are sent).
This section includes the following topics:
• Administrative Distance, page 10-2
• Directly Connected Static Routes, page 10-2
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Information About Static Routing
• Fully Specified Static Routes, page 10-2
• Floating Static Routes, page 10-2
• Remote Next Hops for Static Routes, page 10-3
• BFD, page 10-3
• Virtualization Support, page 10-3
Administrative Distance
An administrative distance is the metric used by routers to choose the best path when there are two or
more routes to the same destination from two different routing protocols. An administrative distance
guides the selection of one routing protocol (or static route) over another, when more than one protocol
adds the same route to the unicast routing table. Each routing protocol is prioritized in order of most to
least reliable using an administrative distance value.
Static routes have a default administrative distance of 1. A router prefers a static route to a dynamic route
because the router considers a route with a low number to be the shortest. If you want a dynamic route
to override a static route, you can specify an administrative distance for the static route. For example, if
you have two dynamic routes with an administrative distance of 120, you would specify an
administrative distance that is greater than 120 for the static route if you want the dynamic route to
override the static route.
Directly Connected Static Routes
You need to specify only the output interface (the interface on which all packets are sent to the
destination network) in a directly connected static route. The router assumes the destination is directly
attached to the output interface and the packet destination is used as the next hop address. The next hop
can be an interface, only for point-to-point interfaces. For broadcast interfaces, the next-hop must be an
IPv4or IPv6 address.
Fully Specified Static Routes
You must specify either the output interface (the interface on which all packets are sent to the destination
network) or the next-hop address in a fully specified static route. You can use a fully specified static route
when the output interface is a multi-access interface and you need to identify the next-hop address. The
next-hop address must be directly attached to the specified output interface.
Floating Static Routes
A floating static route is a static route that the router uses to back up a dynamic route. You must configure
a floating static route with a higher administrative distance than the dynamic route that it backs up. In
this instance, the router prefers a dynamic route to a floating static route. You can use a floating static
route as a replacement if the dynamic route is lost.
Note By default, a router prefers a static route to a dynamic route because a static route has a smaller
administrative distance than a dynamic route.
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Virtualization Support
Remote Next Hops for Static Routes
You can specify the next-hop address of a neighboring router that is not directly connected to the router
for static routes with remote (nondirectly attached) next hops. If a static route has remote next hops
during data-forwarding, the next hops are recursively used in the unicast routing table to identify the
corresponding directly attached next hop(s) that have reachability to the remote next hops.
BFD
Bidirectional forwarding detection (BFD) is supported for Static Routes. BFD is a detection protocol
that provides fast forwarding-path failure detection times. BFD provides subsecond failure detection
between two adjacent devices and can be less CPU-intensive than protocol hello messages because some
of the BFD load can be distributed onto the data plane on supported modules. See the Cisco Nexus 5500
Series NX-OS Interfaces Configuration Guide, Release 6.0 for more information.
Virtualization Support
Static routes support Virtual Routing and Forwarding instances (VRFs).
Licensing Requirements for Static Routing
The following table shows the licensing requirements for this feature:
Prerequisites for Static Routing
Static routing has the following prerequisites:
• The next-hop address for a static route must be reachable or the static route will not be added to the
unicast routing table.
Guidelines and Limitations
Static routing has the following configuration guidelines and limitations:
• You can specify an interface as the next-hop address for a static route only for point-to-point
interfaces such as GRE tunnels.
Product License Requirement
Cisco NX-OS Static routing requires no license. Any feature not included in a license package is bundled with the Cisco
NX-OS system images and is provided at no extra charge to you. For a complete explanation of the Cisco
NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.
Note Make sure the LAN Base Services license is installed on the switch to enable Layer 3 interfaces.
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Default Settings
Default Settings
Table 10-1 lists the default settings for static routing parameters.
Configuring Static Routing
This section includes the following topics:
• Configuring a Static Route, page 10-4
• Configuring Virtualization, page 10-5
Note If you are familiar with the Cisco IOS CLI, be aware that the Cisco NX-OS commands for this feature
might differ from the Cisco IOS commands that you would use.
Configuring a Static Route
You can configure a static route on the router.
SUMMARY STEPS
1. configure terminal
2. ip route {ip-prefix | ip-addr ip-mask} {[next-hop | nh-prefix] | [interface next-hop | nh-prefix]} [tag
tag-value [pref]]
3. (Optional) show ip static-route
4. (Optional) copy running-config startup-config
Table 10-1 Default Static Routing Parameters
Parameters Default
administrative distance 1
RIP feature disabled
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Configuring Static Routing
DETAILED STEPS
This example shows how to configure a static route:
switch# configure terminal
switch(config)# ip route 192.0.2.0/8 192.0.2.10
switch(config)# copy running-config startup-config
Use the no ip static-route command to remove the static route.
Configuring Virtualization
You can configure a static route in a VRF.
SUMMARY STEPS
1. configure terminal
2. vrf context vrf-name
3. ip route {ip-prefix | ip-addr ip-mask} {next-hop | nh-prefix | interface} [tag tag-value [pref]]
4. (Optional) show ip static-route vrf vrf-name
5. (Optional) copy running-config startup-config
Command Purpose
Step 1
configure terminal
Example:
switch# configure terminal
switch(config)#
Enters configuration mode.
Step 2
ip route {ip-prefix | ip-addr ip-mask}
{[next-hop | nh-prefix] | [interface
next-hop | nh-prefix]}
[tag tag-value
[pref]
Example:
switch(config)# ip route 192.0.2.0/8
ethernet 1/2 192.0.2.4
Configures a static route and the interface for this
static route. You can optionally configure the next-hop
address. The preference value sets the administrative
distance. The range is from 1 to 255. The default is 1.
Step 3
show {ip static-route
Example:
switch(config)# show ip static-route
(Optional) Displays information about static routes.
Step 4
copy running-config startup-config
Example:
switch(config)# copy running-config
startup-config
(Optional) Saves this configuration change.
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Verifying the Static Routing Configuration
DETAILED STEPS
This example shows how to configure a static route:
switch# configure terminal
switch(config)# vrf context StaticVrf
switch(config-vrf)# ip route 192.0.2.0/8 192.0.2.10
switch(config-vrf)# copy running-config startup-config
Verifying the Static Routing Configuration
To display the static routing configuration information, use this command:
Configuration Examples for Static Routing
This example shows how to configure static routing:
configure terminal
ip route 192.0.2.0/8 192.0.2.10
copy running-config startup-config
Command Purpose
Step 1
configure terminal
Example:
switch# configure terminal
switch(config)#
Enters configuration mode.
Step 2
vrf context vrf-name
Example:
switch(config)# vrf context StaticVrf
Creates a VRF and enters VRF configuration mode.
Step 3
ip route {ip-prefix | ip-addr ip-mask}
{next-hop | nh-prefix | interface} [tag
tag-value [pref]
Example:
switch(config-vrf)# ip route 192.0.2.0/8
ethernet 1/2
Configures a static route and the interface for this
static route. You can optionally configure the next-hop
address. The preference value sets the administrative
distance. The range is from 1 to 255. The default is 1.
Step 4
show ip static-route vrf vrf-name
Example:
switch(config-vrf)# show ip static-route
(Optional) Displays information on static routes.
Step 5
copy running-config startup-config
Example:
switch(config-vrf)# copy running-config
startup-config
(Optional) Saves this configuration change.
Command Purpose
show ip static-route Displays the configured static routes.
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Additional References
This example shows how to configure static routing for IPv6:
configure terminal
ipv6 route 43::/64 42::2
copy running-config startup-config
Additional References
For additional information related to implementing static routing, see the following sections:
• Related Documents, page 10-7
Related Documents
Related Topic Document Title
Static Routing CLI Cisco Nexus 5000 Series Command Reference, Cisco NX-OS
Releases 4.x, 5.x
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Additional References
