Contents
- IPv6 Routing: Static Routing
- Finding Feature Information
- Prerequisites for IPv6 Routing: Static Routing
- Restrictions for IPv6 Routing: Static Routing
- Information About IPv6 Routing: Static Routing
- Static Routes
- Directly Attached Static Routes
- Recursive Static Routes
- Fully Specified Static Routes
- Floating Static Routes
- How to Configure IPv6 Static Routing
- Configuring a Static IPv6 Route
- Configuring a Recursive IPv6 Static Route to Use a Default IPv6 Static Route
- Configuring a Floating Static IPv6 Route
- Verifying Static IPv6 Route Configuration and Operation
- Configuration Examples for IPv6 Static Routing
- Example: Configuring Manual Summarization
- Example: Configuring Traffic Discard
- Example: Configuring a Fixed Default Route
- Example: Configuring a Floating Static Route
- Additional References
- Feature Information for IPv6 Routing: Static Routing
IPv6 Routing: Static Routing
This feature provides static routing for IPv6. Static routes are manually configured and define an explicit path between two networking devices.
- Finding Feature Information
- Prerequisites for IPv6 Routing: Static Routing
- Restrictions for IPv6 Routing: Static Routing
- Information About IPv6 Routing: Static Routing
- How to Configure IPv6 Static Routing
- Configuration Examples for IPv6 Static Routing
- Additional References
- Feature Information for IPv6 Routing: Static Routing
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table at the end of this module.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Prerequisites for IPv6 Routing: Static Routing
Before configuring the device with a static IPv6 route, you must enable the forwarding of IPv6 packets using the ipv6 unicast-routing global configuration command, enable IPv6 on at least one interface, and configure an IPv6 address on that interface.
Restrictions for IPv6 Routing: Static Routing
You should not configure static configurations over dynamic interfaces, because static configurations will be lost during reboot or when the user disconnects and reconnects the device.
Information About IPv6 Routing: Static Routing
- Static Routes
- Directly Attached Static Routes
- Recursive Static Routes
- Fully Specified Static Routes
- Floating Static Routes
Static Routes
Networking devices forward packets using route information that is either manually configured or dynamically learned using a routing protocol. Static routes are manually configured and define an explicit path between two networking devices. Unlike a dynamic routing protocol, static routes are not automatically updated and must be manually reconfigured if the network topology changes. The benefits of using static routes include security and resource efficiency. Static routes use less bandwidth than dynamic routing protocols and no CPU cycles are used to calculate and communicate routes. The main disadvantage to using static routes is the lack of automatic reconfiguration if the network topology changes.
Static routes can be redistributed into dynamic routing protocols but routes generated by dynamic routing protocols cannot be redistributed into the static routing table. No algorithm exists to prevent the configuration of routing loops that use static routes.
Static routes are useful for smaller networks with only one path to an outside network and to provide security for a larger network for certain types of traffic or links to other networks that need more control. In general, most networks use dynamic routing protocols to communicate between networking devices but may have one or two static routes configured for special cases.
Directly Attached Static Routes
In directly attached static routes, only the output interface is specified. The destination is assumed to be directly attached to this interface, so the packet destination is used as the next-hop address. This example shows such a definition:
ipv6 route 2001:DB8::/32 ethernet1/0
The example specifies that all destinations with address prefix 2001:DB8::/32 are directly reachable through interface Ethernet1/0.
Directly attached static routes are candidates for insertion in the IPv6 routing table only if they refer to a valid IPv6 interface; that is, an interface that is both up and has IPv6 enabled on it.
Recursive Static Routes
In a recursive static route, only the next hop is specified. The output interface is derived from the next hop. This definition is shown in the following example:
ipv6 route 2001:DB8::/32 2001:DB8:3000:1
This example specifies that all destinations with address prefix 2001:DB8::/32 are reachable via the host with address 2001:DB8:3000:1.
A recursive static route is valid (that is, it is a candidate for insertion in the IPv6 routing table) only when the specified next hop resolves, either directly or indirectly, to a valid IPv6 output interface, provided the route does not self-recurse, and the recursion depth does not exceed the maximum IPv6 forwarding recursion depth.
A route self-recurses if it is itself used to resolve its own next hop. For example, suppose we have the following routes in the IPv6 routing table:
IPv6 Routing Table - 9 entries
Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP
U - Per-user Static route
I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea
O - OSPF intra, OI - OSPF inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
R 2001:DB8::/32 [130/0]
via ::, Serial2/0
B 2001:DB8:3000:0/16 [200/45]
Via 2001:DB8::0104
The following examples defines a recursive IPv6 static route:
ipv6 route 2001:DB8::/32 2001:0BD8:3000:1
This static route will not be inserted into the IPv6 routing table because it is self-recursive. The next hop of the static route, 2001:DB8:3000:1, resolves via the BGP route 2001:DB8:3000:0/16, which is itself a recursive route (that is, it only specifies a next hop). The next hop of the BGP route, 2001:DB8::0104, resolves via the static route. Therefore, the static route would be used to resolve its own next hop.
It is not normally useful to manually configure a self-recursive static route, although it is not prohibited. However, a recursive static route that has been inserted in the IPv6 routing table may become self-recursive as a result of some transient change in the network learned through a dynamic routing protocol. If this occurs, the fact that the static route has become self-recursive will be detected and it will be removed from the IPv6 routing table, although not from the configuration. A subsequent network change may cause the static route to no longer be self-recursive, in which case it will be reinserted in the IPv6 routing table.
Fully Specified Static Routes
In a fully specified static route, both the output interface and the next hop are specified. This form of static route is used when the output interface is a multi-access one and it is necessary to explicitly identify the next hop. The next hop must be directly attached to the specified output interface. The following example shows a definition of a fully specified static route:
ipv6 route 2001:DB8:/32 ethernet1/0 2001:DB8:3000:1
A fully specified route is valid (that is, a candidate for insertion into the IPv6 routing table) when the specified IPv6 interface is IPv6-enabled and up.
Floating Static Routes
Floating static routes are static routes that are used to back up dynamic routes learned through configured routing protocols. A floating static route is configured with a higher administrative distance than the dynamic routing protocol it is backing up. As a result, the dynamic route learned through the routing protocol is always used in preference to the floating static route. If the dynamic route learned through the routing protocol is lost, the floating static route will be used in its place. The following example defines a floating static route:
ipv6 route 2001:DB8:/32 ethernet1/0 2001:DB8:3000:1 210
Any of the three types of IPv6 static routes can be used as a floating static route. A floating static route must be configured with an administrative distance that is greater than the administrative distance of the dynamic routing protocol, because routes with smaller administrative distances are preferred.
 Note | By default, static routes have smaller administrative distances than dynamic routes, so static routes will be used in preference to dynamic routes. |
How to Configure IPv6 Static Routing
- Configuring a Static IPv6 Route
- Configuring a Recursive IPv6 Static Route to Use a Default IPv6 Static Route
- Configuring a Floating Static IPv6 Route
- Verifying Static IPv6 Route Configuration and Operation
Configuring a Static IPv6 Route
1.
enable
2.
configure
terminal
3.
ipv6
route
ipv6-prefix
/
prefix-length
ipv6-address
|
interface-type
interface-number
ipv6-address]} [administrative-distance] [administrative-multicast-distance |
unicast|
multicast] [tag
tag]
DETAILED STEPS
Configuring a Recursive IPv6 Static Route to Use a Default IPv6 Static Route
By default, a recursive IPv6 static route will not resolve using the default route (::/0). Perform this task to restore legacy behavior and allow resolution using the default route.
1.
enable
2.
configure
terminal
3.
ipv6
route
static
resolve
default
DETAILED STEPS
Configuring a Floating Static IPv6 Route
1.
enable
2.
configure
terminal
3.
ipv6
route
ipv6-prefix
/
prefix-length
{ipv6-address |
interface-type
interface-number
ipv6-address]} [administrative-distance] [administrative-multicast-distance |
unicast |
multicast] [tag
tag]
DETAILED STEPS
Verifying Static IPv6 Route Configuration and Operation
1.
enable
3.
debug
ipv6
routing
DETAILED STEPS
Configuration Examples for IPv6 Static Routing
Static routes may be used for a variety of purposes. Common usages include the following:
In many cases, alternative mechanisms exist within Cisco software to achieve the same objective. Whether to use static routes or one of the alternative mechanisms depends on local circumstances.
- Example: Configuring Manual Summarization
- Example: Configuring Traffic Discard
- Example: Configuring a Fixed Default Route
- Example: Configuring a Floating Static Route
Example: Configuring Manual Summarization
The following example shows a static route being used to summarize local interface prefixes advertised into RIP. The static route also serves as a discard route, discarding any packets received by the device to a 2001:DB8:1::/48 destination not covered by a more specific interface prefix.
Device> enable
Device# configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Device(config)# interface ethernet0/0
Device(config-if)# ipv6 address 2001:DB8:2:1234/64
Device(config-if)# exit
Device(config)#
Device(config)# interface ethernet1/0
Device(config-if)# ipv6 address 2001:DB8:3:1234/64
Device(config-if)# exit
Device(config)# interface ethernet2/0
Device(config-if)# ipv6 address 2001:DB8:4:1234/64
Device(config-if)# exit
Device(config)# interface ethernet3/0
Device(config-if)# ipv6 address 2001:DB8::1234/64
Device(config-if)# ipv6 rip one enable
Device(config-if)# exit
Device(config)# ipv6 Device rip one
Device(config-rtr)# redistribute static
Device(config-rtr)# exit
Device(config)# ipv6 route 2001:DB8:1:1/48 null0
Device(config)# end
00:01:30: %SYS-5-CONFIG_I: Configured from console by console
Device# show ipv6 route static
IPv6 Routing Table - 3 entries
Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP
U - Per-user Static route
I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea, IS - ISIS summary
O - OSPF intra, OI - OSPF inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
S 2001:DB8:1::/48 [1/0]
via ::, Null0
Example: Configuring Traffic Discard
Configuring a static route to point at interface null0 may be used for discarding traffic to a particular prefix. For example, if it is required to discard all traffic to prefix 2001:DB8:42:1/64, the following static route would be defined:
Device> enable Device# configure terminal Enter configuration commands, one per line. End with CNTL/Z. Device(config)# ipv6 route 2001:DB8:42:1::/64 null0 Device(config)# end
Example: Configuring a Fixed Default Route
A default static route is often used in simple device topologies. In the following example, a device is connected to its local site via Ethernet0/0 and to the main corporate network via Serial2/0 and Serial3/0. All nonlocal traffic will be routed over the two serial interfaces.
Device(config)# interface ethernet0/0
Device(config-if)# ipv6 address 2001:DB8:17:1234/64
Device(config-if)# exit
Device(config)# interface Serial2/0
Device(config-if)# ipv6 address 2001:DB8:1:1234/64
Device(config-if)# exit
Device(config)# interface Serial3/0
Device(config-if)# ipv6 address 2001:DB8:2:124/64
Device(config-if)# exit
Device(config)# ipv6 route ::/0 Serial2/0
Device(config)# ipv6 route ::/0 Serial3/0
Device(config)# end
Device#
00:06:30: %SYS-5-CONFIG_I: Configured from console by console
Device# show ipv6 route static
IPv6 Routing Table - 7 entries
Codes: C - Connected, L - Local, S - Static, R - RIP, B - BGP
U - Per-user Static route
I1 - ISIS L1, I2 - ISIS L2, IA - ISIS interarea, IS - ISIS summary
O - OSPF intra, OI - OSPF inter, OE1 - OSPF ext 1, OE2 - OSPF ext 2
ON1 - OSPF NSSA ext 1, ON2 - OSPF NSSA ext 2
S ::/0 [1/0]
via ::, Serial2/0
via ::, Serial3/0
Example: Configuring a Floating Static Route
A floating static route often is used to provide a backup path in the event of connectivity failure. In the following example, the device has connectivity to the network core via Serial2/0 and learns the route 2001:DB8:1:1/32 via IS-IS. If the Serial2/0 interface fails, or if route 2001:DB8:1:1/32 is no longer learned via IS-IS (indicating loss of connectivity elsewhere in the network), traffic is routed via the backup ISDN interface.
Device> enable Device# configure terminal Enter configuration commands, one per line. End with CNTL/Z. Device(config)# interface ethernet0/0 Device(config-if)# ipv6 address 2001:DB8:17:1234/64 Device(config-if)# exit Device(config)# interface Serial2/0 Device(config-if)# ipv6 address 2001:DB8:1:1234/64 Device(config-if)# ipv6 router isis Device(config-if)# exit Device(config)# router isis Device(config-rtr)# net 42.0000.0000.0000.0001.00 Device(config-rtr)# exit Device(config)# interface BRI1/0 Device(config-if)# encapsulation ppp Device(config-if)# ipv6 enable Device(config-if)# isdn switch-type basic-net3 Device(config-if)# ppp authentication chap optional Device(config-if)# ppp multilink Device(config-if)# exit Device(config)# dialer-list 1 protocol ipv6 permit Device(config)# ipv6 route 2001:DB8:1::/32 BRI1/0 200 Device(config)# end Device# 00:03:07: %SYS-5-CONFIG_I: Configured from console by console 2001:DB8:5000:)/16, interface Ethernet3/0, distance 1
Additional References
Related Documents
Related Topic |
Document Title |
|---|---|
|
Cisco IOS commands |
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IPv6 addressing and connectivity |
IPv6 Configuration Guide |
|
IPv6 commands |
|
|
Cisco IOS IPv6 features |
|
IP Routing Protocol-Independent Features |
IP Routing Protocol-Independent Configuration Guide |
Standards and RFCs
Standard/RFC |
Title |
|---|---|
|
RFCs for IPv6 |
IPv6 RFCs |
MIBs
|
MIB |
MIBs Link |
|---|---|
|
|
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL: |
Technical Assistance
Description |
Link |
|---|---|
|
The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password. |
Feature Information for IPv6 Routing: Static Routing
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Feature Name |
Releases |
Feature Information |
|---|---|---|
|
IPv6 Routing: Static Routing |
12.0(22)S 12.2(2)T 12.2(14)S 12.2(17a)SX1 12.2(25)SG 12.2(28)SB 12.2(33)SRA Cisco IOS XE Release 2.1 |
Static routes are manually configured and define an explicit path between two networking devices. The following commands were introduced or modified: ipv6 route, ipv6 route static resolve default, show ipv6 route, show ipv6 static. |