Table Of Contents

Network Stack IPv4 and IPv6 Commands on Cisco IOS XR Software

clear ipv6 neighbors

icmp ipv4 rate-limit unreachable

ipv4 address (network)

ipv4 assembler max-packets

ipv4 assembler timeout

ipv4 conflict-policy

ipv4 directed-broadcast

ipv4 helper-address

ipv4 mask-reply

ipv4 mtu

ipv4 redirects

ipv4 source-route

ipv4 unnumbered (point-to-point)

ipv4 unreachables disable

ipv4 virtual address

ipv6 address

ipv6 address link-local

ipv6 conflict-policy

ipv6 enable

ipv6 hop-limit

ipv6 icmp error-interval

ipv6 mtu

ipv6 nd dad attempts

ipv6 nd managed-config-flag

ipv6 nd ns-interval

ipv6 nd other-config-flag

ipv6 nd prefix

ipv6 nd ra-interval

ipv6 nd ra-lifetime

ipv6 nd reachable-time

ipv6 nd redirects

ipv6 nd scavenge-timeout

ipv6 nd suppress-ra

ipv6 neighbor

ipv6 unreachables disable

local pool

show arm conflicts

show arm database

show arm router-ids

show arm registrations producers

show arm summary

show arm vrf-summary

show clns statistics

show ipv4 interface

show local pool

show ipv4 traffic

show ipv6 interface

show ipv6 neighbors

show ipv6 neighbors summary

show ipv6 traffic

show mpa client

show mpa groups

show mpa ipv4

show mpa ipv6

Network Stack IPv4 and IPv6 Commands on Cisco IOS XR Software

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This chapter describes the commands available in the Cisco IOS XR software to configure and monitor features related to IP Version 4 (IPv4) and IP Version 6 (IPv6).

For detailed information about network stack concepts, configuration tasks, and examples, refer to the Implementing Network Stack IPv4 and IPv6 on Cisco IOS XR Software configuration module.

clear ipv6 neighbors

To delete all entries in the IPv6 neighbor discovery cache, except static entries, use the clear ipv6 neighbors command in EXEC mode.

clear ipv6 neighbors [location node-id]

Syntax Description

location node-id

(Optional) The designated node. The node-id argument is entered in the rack/slot/module notation.

Defaults

No default behavior or values

Command Modes

EXEC

Command History

Release	Modification
Release 2.0	This command was introduced on the Cisco CRS-1.
Release 3.0	No modification.
Release 3.2	This command was supported on the Cisco XR 12000 Series Router.
Release 3.3.0	No modification.
Release 3.4.0	No modification.
Release 3.5.0	No modification.
Release 3.6.0	No modification.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

If the location option is specified, only the neighbor entries specified in the location node-id keyword and argument are cleared.

Task ID

Task ID	Operations
network	read, write
IPv6	execute

Examples

In the following example, only the highlighted entry is deleted:

RP/0/RP0/CPU0:router# clear ipv6 neighbors ? 

location specify a node name 

RP/0/RP0/CPU0:router# show ipv6 neighbor

IPv6 Address Age Link-layer Addr State Interface 

8888::3 - 1234.2345.9877 REACH POS 0/0/0/0

8888::8 - 1234.2345.9877 REACH POS0 /0/0/0

fe80::205:1ff:fe9f:6400 1335 0005.019f.6400 STALE POS 0/0/0/0

fe80::206:d6ff:fece:3808 1482 0006.d6ce.3808 STALE POS 0/0/0/0

fe80::200:11ff:fe11:1112 1533 0000.1111.1112 STALE POS 0/2/0/2 

RP/0/RP0/CPU0:router# clear ipv6 neighbors location 0/2/0 

RP/0/RP0/CPU0:router# show ipv6 neighbor 

IPv6 Address Age Link-layer Addr State Interface 

8888::3 - 1234.2345.9877 REACH POS 0/0/0/0 

8888::8 - 1234.2345.9877 REACH POS 0/0/0/0 

fe80::205:1ff:fe9f:6400 1387 0005.019f.6400 STALE POS 0/0/0/0 

fe80::206:d6ff:fece:3808 1534 0006.d6ce.3808 STALE POS 0/0/0/0 

icmp ipv4 rate-limit unreachable

To limit the rate that IPv4 Internet Control Message Protocol (ICMP) destination unreachable messages are generated, use the icmp ipv4 rate-limit unreachable command in global configuration mode. To remove the rate limit, use the no form of this command.

icmp ipv4 rate-limit unreachable [DF] milliseconds

no icmp ipv4 rate-limit unreachable [DF] milliseconds

Syntax Description

DF	(Optional) Limits the rate at which ICMP destination unreachable messages are sent when code 4 fragmentation is needed and data fragmentation is (DF) set, as specified in the IP header of the ICMP destination unreachable message.
milliseconds	Time period (in milliseconds) between the sending of ICMP destination unreachable messages. Range is 1 to 4294967295.

Defaults

The default value is one ICMP destination unreachable message every 500 milliseconds.

Command Modes

Global configuration

Command History

Release	Modification
Release 2.0	This command was introduced on the Cisco CRS-1.
Release 3.0	No modification.
Release 3.2	This command was supported on the Cisco XR 12000 Series Router.
Release 3.3.0	No modification.
Release 3.4.0	No modification.
Release 3.5.0	No modification.
Release 3.6.0	No modification.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

The Cisco IOS XR software maintains two timers: one for general destination unreachable messages and one for DF destination unreachable messages. Both share the same time limits and defaults. If the DF option is not configured, the icmp ipv4 rate-limit unreachable command sets the time values for DF destination unreachable messages. If the DF option is configured, its time values remain independent from those of general destination unreachable messages.

Task ID

Task ID	Operations
ipv4	read, write
network	read, write

Examples

The following example shows how to set the rate of the ICMP destination unreachable message to one message every 10 milliseconds:

RP/0/RP0/CPU0:router(config)# icmp ipv4 rate-limit unreachable 10

ipv4 address (network)

To set a primary or secondary IPv4 address for an interface, use the ipv4 address command in interface configuration mode. To remove an IPv4 address, use the no form of this command.

ipv4 address ipv4-address mask [secondary]

no ipv4 address ipv4-address mask [secondary]

Syntax Description

ipv4-address	IPv4 address.
mask	Mask for the associated IP subnet. The network mask can be specified in either of two ways: •The network mask can be a four-part dotted decimal address. For example, 255.0.0.0 indicates that each bit equal to 1 means the corresponding address bit belongs to the network address. •The network mask can be indicated as a slash (/) and number. For example, /8 indicates that the first 8 bits of the mask are ones, and the corresponding bits of the address are network address.
secondary	(Optional) Specifies that the configured address is a secondary IPv4 address. If this keyword is omitted, the configured address is the primary IPv4 address.

Defaults

No IPv4 address is defined for the interface.

Command Modes

Interface configuration

Command History

Release	Modification
Release 2.0	This command was introduced on the Cisco CRS-1.
Release 3.0	No modification.
Release 3.2	This command was supported on the Cisco XR 12000 Series Router.
Release 3.3.0	No modification.
Release 3.4.0	No modification.
Release 3.5.0	No modification.
Release 3.6.0	No modification

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

An interface can have one primary IPv4 address and multiple secondary IPv4 addresses. Packets generated by the software always use the primary IPv4 address. Therefore, all networking devices on a segment should share the same primary network number.

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Note The same IPv4 address configured on two different interfaces causes an error message to display that indicates the conflict. The interface located in the highest rack, slot, module, instance, and port is disabled.

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Hosts can determine subnet masks using the IPv4 Internet Control Message Protocol (ICMP) mask request message. Networking devices respond to this request with an ICMP mask reply message.

You can disable IPv4 processing on a particular interface by removing its IPv4 address with the no ipv4 address command. If the software detects another host using one of its IPv4 addresses, it will display an error message on the console.

The optional secondary keyword allows you to specify an unlimited number of secondary addresses. Secondary addresses are treated like primary addresses, except that the system never generates datagrams other than routing updates with secondary source addresses. IPv4 broadcasts and Address Resolution Protocol (ARP) requests are handled properly, as are interface routes in the IP routing table.

Secondary IPv4 addresses can be used in a variety of situations. The following are the most common applications:

•There may not be enough host addresses for a particular network segment. For example, your subnetting allows up to 254 hosts per logical subnet, but on one physical subnet you need to have 300 host addresses. Using secondary IPv4 addresses on the networking devices allows you to have two logical subnets using one physical subnet.

•Many older networks were built using Level 2 bridges. The judicious use of secondary addresses can aid in the transition to a subnetted, router-based network. Routers on an older, bridged segment can be easily made aware that there are many subnets on that segment.

Task ID

Task ID	Operations
ipv4	read, write
network	read, write

Examples

The following example shows how to set 192.168.1.27 as the primary address and 192.168.7.17 and 192.168.8.17 as the secondary addresses on POS interface 0/1/1/0:

RP/0/RP0/CPU0:router(config)# interface POS 0/1/1/0

RP/0/RP0/CPU0:router(config-if)# ipv4 address 192.168.1.27 255.255.255.0

RP/0/RP0/CPU0:router(config-if)# ipv4 address 192.168.7.17 255.255.255.0 secondary

RP/0/RP0/CPU0:router(config-if)# ipv4 address 192.168.8.17 255.255.255.0 secondary

Related Commands

Command	Description
show ipv4 interface	Lists a summary of IPv4 information and status for the interface.

ipv4 assembler max-packets

To configure the maximum number of packets that are allowed in assembly queues, use the ipv4 assembler max-packets command in global configuration mode. To disable this feature, use the no from of this command.

ipv4 assembler max-packets percentage value

no ipv4 assembler max-packets percentage value

Syntax Description

percentage value

Percentage of total packets available in the system. The range is from 1 to 50.

Command Modes

Global configuration

Command History

Release	Modification
Release 3.6.0	This command was introduced on the Cisco CRS-1 and Cisco XR 12000 Series Router.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

Task ID

Task ID	Operations
ipv4	read, write
network	read, write

Examples

The following example shows how to configure the maximum number of packets for the assembly queue:

RP/0/RP0/CPU0:router(config)# ipv4 assembler max-packets 35

Related Commands

Command	Description
ipv4 assembler timeout	Configures the number of seconds an assembly queue can hold before a timeout occurs.

ipv4 assembler timeout

To configure the number of seconds an assembly queue can hold before a timeout occurs, use the ipv4 assembler timeout command in global configuration mode. To disable this feature, use the no form of this command.

ipv4 assembler timeout seconds

no ipv4 assembler timeout seconds

Syntax Description

seconds

Number of seconds an assembly queue can hold before a timeout occurs. The range is from 1 to 120.

Command Modes

Global configuration

Command History

Release	Modification
Release 3.6.0	This command was introduced on the Cisco CRS-1 and Cisco XR 12000 Series Router.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

Task ID

Task ID	Operations
ipv4	read, write
network	read, write

Examples

The following example shows how to configure an assembly queue before a timeout occurs:

RP/0/RP0/CPU0:router(config)# ipv4 assembler timeout 88

Related Commands

Command	Description
ipv4 assembler max-packets	Configures the maximum number of packets that are allowed in assembly queues.

ipv4 conflict-policy

To enable IP Address Repository Manager (IPARM) conflict resolution, use the ipv4 conflict-policy command in global configuration mode. To disable the IPARM conflict resolution, use the no form of the command.

ipv4 conflict-policy {highest-ip | longest-prefix | static}

no ipv4 conflict-policy {highest-ip | longest-prefix | static}

Syntax Description

highest-ip	Keeps the highest ip address in the conflict set.
longest-prefix	Keeps the longest prefix match in the conflict set.
static	Keeps the existing interface running across new address configurations.

Defaults

The precedence rule adopted is loopback > physical > other virtual interfaces. Within virtual interfaces, there is an alphabetical preference, for example, loopback1 > loopback2 and bundle-ether > bundle-pos > tunnel. Among physical interfaces, the lower rack or slot takes control.

Command Modes

Global configuration

Command History

Release	Modification
Release 3.2	This command was introduced on the Cisco CRS-1.

Release 3.3.0	No modification.
Release 3.4.0	No modification.
Release 3.5.0	No modification.
Release 3.6.0	No modification.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

Use ipv4 conflict-policy command to set an IPARM policy that resolves a conflict in the configured addresses. The policy tells IPARM what address to select from the addresses in conflict. The policy then forces the address in conflict to become inactive.

Task ID

Task ID	Operations
ipv4	read, write
ip-services	read, write

Examples

The following example shows how to enable the static policy for conflict resolution:

RP/0/RP0/CPU0:router(config)# ipv6 conflict-policy static

Related Commands

Command	Description
show arm conflicts	Displays the IPv4 or IPv6 address conflict information.

ipv4 directed-broadcast

To enable forwarding of IPv4 directed broadcasts on an interface, use the ipv4 directed-broadcast command in interface configuration mode. To disable forwarding of IPv4 directed broadcast on an interface, use the no form of this command.

ipv4 directed-broadcast

no ipv4 directed-broadcast

Syntax Description

This command has no arguments or keywords.

Defaults

By default, directed broadcasts are dropped.

Command Modes

Interface configuration

Command History

Release	Modification
Release 2.0	This command was introduced on the Cisco CRS-1.
Release 3.0	No modification.
Release 3.2	This command was supported on the Cisco XR 12000 Series Router.
Release 3.3.0	No modification.
Release 3.4.0	No modification.
Release 3.5.0	No modification.
Release 3.6.0	No modification.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

A directed broadcast is a packet sent to a specific network. IPv4 directed broadcasts are dropped and not forwarded. Dropping IPv4 directed broadcasts makes routers less susceptible to denial-of-service (DoS) attacks.

Task ID

Task ID	Operations
ipv4	read, write
network	read, write

Examples

The following example shows how to enable the forwarding of IPv4 directed broadcasts on POS interface 0/1/1/0:

RP/0/RP0/CPU0:router(config)# interface POS 0/1/1/0

RP/0/RP0/CPU0:router(config-if)# ipv4 directed-broadcast

Related Commands

Command	Description
show ipv4 interface	Displays statistics for all interfaces configured for IPv4.
show ipv4 interface	Lists a summary of IPv4 information and status for the interface.
ipv4 unnumbered (point-to-point)	Enables IP processing on a point-to-point interface without assigning an explicit IP address to the interface.

ipv4 helper-address

To configure the address to which the software forwards User Datagram Protocol (UDP) broadcasts, including BOOTP, received on an interface, use the ipv4 helper-address command in interface configuration mode. To remove an IPv4 helper address, use the no form of this command.

ipv4 helper-address [vrf vrf-name] | [destination-address]

no ipv4 helper-address [vrf vrf-name] | [destination-address]

Syntax Description

vrf	(Optional) Displays VPN routing and forwarding (VRF) instance information.
vrf-name	(Optional) Name of a VRF.
destination-address	Destination broadcast or host address to be used when UDP broadcasts are forwarded. There can be more than one helper address per interface.

Defaults

IPv4 helper addresses are disabled. Default vrf is assumed if the vrf is not specified.

Command Modes

Interface configuration

Command History

Release	Modification
Release 2.0	This command was introduced on the Cisco CRS-1.
Release 3.0	No modification.
Release 3.2	This command was supported on the Cisco XR 12000 Series Router.
Release 3.3.0	The vrf keyword and vrf-name argument were added.
Release 3.4.0	No modification.
Release 3.5.0	No modification.
Release 3.6.0	No modification.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

Use this command with the forward-protocol udp command in global configuration mode, which specifies by port number the broadcast packets that are forwarded. UDP is enabled by default for well-known ports. The ipv4 helper-address command specifies the destination to which the UDP packets are forwarded.

One common application that requires IPv4 helper addresses is Dynamic Host Configuration Protocol (DHCP), which is defined in RFC 1531. DHCP protocol information is carried inside of BOOTP packets. To enable BOOTP broadcast forwarding for a set of clients, configure an IPv4 helper address on the networking device interface physically closest to the client. The IPv4 helper address should specify the address of the DHCP server. If you have multiple servers, you can configure one IPv4 helper address for each server. Because BOOTP packets are forwarded by default, DHCP information can now be forwarded by the networking device. The DHCP server now receives broadcasts from the DHCP clients.

Task ID

Task ID	Operations
ipv4	read, write
network	read, write

Examples

The following example shows how to specify that all UDP broadcast packets received on POS interface 0/1/1/0 are forwarded to 192.168.1.0:

RP/0/RP0/CPU0:router(config)# interface POS 0/1/1/0

RP/0/RP0/CPU0:router(config-if)# ipv4 helper-address 192.168.1.0

Related Commands

Command	Description
forward-protocol udp	Specifies which ports the networking device forwards to when forwarding broadcast packets.

ipv4 mask-reply

To enable the Cisco IOS XR software to respond to IPv4 Internet Control Message Protocol (ICMP) mask requests by sending ICMP mask reply messages, use the ipv4 mask-reply command in interface configuration mode. To restore the default, use the no form of this command.

ipv4 mask-reply

no ipv4 mask-reply

Syntax Description

This command has no arguments or keywords.

Defaults

IPv4 mask replies are not sent.

Command Modes

Interface configuration

Command History

Release	Modification
Release 2.0	This command was introduced on the Cisco CRS-1.
Release 3.0	No modification.
Release 3.2	This command was supported on the Cisco XR 12000 Series Router.
Release 3.3.0	No modification.
Release 3.4.0	No modification.
Release 3.5.0	No modification.
Release 3.6.0	No modification.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

This command enables the Cisco IOS XR software to respond to IPv4 ICMP mask requests by sending ICMP mask reply messages.

Task ID

Task ID	Operations
ipv4	read, write
network	read, write

Examples

The following example enables the sending of ICMP mask reply messages on POS interface 0/1/1/0:

RP/0/RP0/CPU0:router(config)# interface POS 0/1/1/0 

RP/0/RP0/CPU0:router(config-if)# ipv4 mask-reply

ipv4 mtu

To set the maximum transmission unit (MTU) size of IPv4 packets sent on an interface, use the ipv4 mtu command in interface configuration mode. To restore the default MTU size, use the no form of this command.

ipv4 mtu bytes

no ipv4 mtu

Syntax Description

bytes

MTU in bytes. Range is 68 to 65535 bytes for IPv4 packets. The maximum MTU size that can be set on an interface depends on the interface medium.

Defaults

If no MTU size is configured for IPv4 packets sent on an interface, the interface derives the MTU from the Layer 2 MTU.

Command Modes

Interface configuration

Command History

Release	Modification
Release 2.0	This command was introduced on the Cisco CRS-1.
Release 3.0	No modification.
Release 3.2	This command was supported on the Cisco XR 12000 Series Router.
Release 3.3.0	No modification.
Release 3.4.0	No modification.
Release 3.5.0	No modification.
Release 3.6.0	No modification.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

The router will fragment any IPv4 packet that exceeds the MTU set for the interface.

The maximum MTU size that can be set on an interface depends on the interface medium. If the Layer 2 MTU is smaller than the Layer 3 MTU, the Cisco IOS XR software uses the Layer 2 MTU value for the Layer 3 MTU. Conversely, if the Layer 3 MTU is smaller than the Layer 2 MTU, the software uses Layer 3 MTU value. In other words the Cisco IOS XR software uses the lower of the two values for the MTU.

All devices on a physical medium must have the same protocol MTU to operate.

---

Note Changing the MTU value (with the mtu interface configuration command) can affect the IPv4 MTU value. If the current IPv4 MTU value is the same as the MTU value, and you change the MTU value, the IPv4 MTU value will be modified automatically to match the new MTU. However, the reverse is not true; changing the IPv4 MTU value has no effect on the value for the mtu command.

---

Task ID

Task ID	Operations
ipv4	read, write
network	read, write

Examples

The following example shows how to set the maximum IPv4 packet size for POS interface 0/1/1/0 to 300 bytes:

RP/0/RP0/CPU0:router(config)# interface POS 0/1/1/0

RP/0/RP0/CPU0:router(config-if)# ipv4 mtu 300

Related Commands

Command	Description
show ipv4 interface	Displays the MTU status of interfaces configured for IPv4.

ipv4 redirects

To enable the sending of IPv4 Internet Control Message Protocol (ICMP) redirect messages if the software is forced to resend a packet through the same interface on which it was received, use the ipv4 redirects command in interface configuration mode. To restore the default, use the no form of this command.

ipv4 redirects

no ipv4 redirects

Syntax Description

This command has no arguments or keywords.

Defaults

ICMP redirect messages are disabled by default on the interface unless the Hot Standby Router Protocol (HSRP) is configured.

Command Modes

Interface configuration

Command History

Release	Modification
Release 2.0	This command was introduced on the Cisco CRS-1.
Release 3.0	No modification.
Release 3.2	This command was supported on the Cisco XR 12000 Series Router.
Release 3.3.0	No modification.
Release 3.4.0	No modification.
Release 3.5.0	No modification.
Release 3.6.0	No modification.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

If HSRP is configured on an interface, ICMP redirect messages are disabled by default on that interface.

Task ID

Task ID	Operations
ipv4	read, write
network	read, write

Examples

The following example shows how to disable the sending of ICMP IPv4 redirect messages on POS interface 0/1/1/0:

RP/0/RP0/CPU0:router(config)# interface POS 0/1/1/0

RP/0/RP0/CPU0:router(config-if)# ipv4 redirects

ipv4 source-route

To allow the processing of any IPv4 datagrams containing a source-route header option, use the ipv4 source-route command in global configuration mode. To have the software discard any IP datagram that contains a source-route option, use the no form of this command.

ipv4 source-route

no ipv4 source-route

Syntax Description

This command has no arguments or keywords.

Defaults

The software discards any IPv4 datagrams containing a source-route header option.

Command Modes

Global configuration

Command History

Release	Modification
Release 2.0	This command was introduced on the Cisco CRS-1.
Release 3.0	No modification.
Release 3.2	This command was supported on the Cisco XR 12000 Series Router.
Release 3.3.0	No modification.
Release 3.4.0	No modification.
Release 3.5.0	The following sections were modified: •Command description •Defaults •Usage Guidelines
Release 3.6.0	No modification.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

By default, any IPv4 datagram which contains a source-route header option is discarded.

Task ID

Task ID	Operations
ipv4	read, write
network	read, write

Examples

The following example shows how to allow the processing of any IPv4 datagrams containing a source-route header option:

RP/0/RP0/CPU0:router(config)# ipv4 source-route

ipv4 unnumbered (point-to-point)

To enable IPv4 processing on a point-to-point interface without assigning an explicit IPv4 address to that interface, use the ipv4 unnumbered command in interface configuration mode. To disable this feature, use the no form of this command.

ipv4 unnumbered interface-type interface-instance

no ipv4 unnumbered interface-type interface-instance

Syntax Description

interface-type

Interface type. For more information, use the question mark (?) online help function.

interface-instance

Either a physical interface instance or a virtual interface instance as follows: •Physical interface instance. Naming notation is rack/slot/module/port and a slash between values is required as part of the notation. –rack: Chassis number of the rack. –slot: Physical slot number of the modular services card or line card. –module: Module number. A physical layer interface module (PLIM) is always 0. –port: Physical port number of the interface. Note In references to a Management Ethernet interface located on a route processor card, the physical slot number is alphanumeric (RP0 or RP1) and the module is CPU0. Example: interface MgmtEth0/RP1/CPU0/0. •Virtual interface instance. Number range varies depending on interface type. For more information about the syntax for the router, use the question mark (?) online help function.

Defaults

IPv4 processing on a point-to-point interface is disabled unless an IPv4 address is assigned explicitly to that interface.

Command Modes

Interface configuration

Command History

Release	Modification
Release 2.0	This command was introduced on the Cisco CRS-1.
Release 3.0	No modification.
Release 3.2	This command was supported on the Cisco XR 12000 Series Router.
Release 3.3.0	No modification.
Release 3.4.0	No modification.
Release 3.5.0	No modification.
Release 3.6.0	No modification.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

Whenever the unnumbered interface generates a packet (for example, for a routing update), it uses the address of the specified interface as the source address of the IPv4 packet. It also uses the IPv4 address of the specified interface in determining which routing processes are sending updates over the unnumbered interface. Restrictions include the following:

•Packet-over-SONET (POS) interfaces using High-Level Data Link Control (HDLC), PPP, and tunnel interfaces can be unnumbered.

•You cannot use the ping EXEC command to determine whether the interface is up because the interface has no address. Simple Network Management Protocol (SNMP) can be used to remotely monitor interface status.

The interface you specify by the interface-type and interface-number arguments must be enabled (listed as "up" in the show interfaces command display).

If you are configuring Intermediate System-to-Intermediate System (IS-IS) across a POS interface, you should configure the POS interface as unnumbered. This strategy allows you to conform to RFC 1195, which states that IP addresses are not required on each interface.

Task ID

Task ID	Operations
ipv4	read, write
network	read, write

Examples

In the following example, POS interface 0/1/1/0 is assigned the loopback interface address 5:

RP/0/RP0/CPU0:router(config)# interface loopback 5

RP/0/RP0/CPU0:router(config-if)# ipv4 address 192.168.6.6 255.255.255.0

RP/0/RP0/CPU0:router(config)# interface POS 0/1/1/0

RP/0/RP0/CPU0:router(config-if)# ipv4 unnumbered loopback 5

ipv4 unreachables disable

To disable the generation of IPv4 Internet Control Message Protocol (ICMP) unreachable messages, use the ipv4 unreachables command in interface configuration mode. To re-enable the generation of ICMP unreachable messages, use the no form of this command.

ipv4 unreachables disable

no ipv4 unreachables disable

Syntax Description

This command has no arguments or keywords.

Defaults

IPv4 ICMP unreachables messages are generated.

Command Modes

Interface configuration

Command History

Release	Modification
Release 2.0	This command was introduced on the Cisco CRS-1.
Release 3.0	No modification.
Release 3.2	This command was supported on the Cisco XR 12000 Series Router.
Release 3.3.0	No modification.
Release 3.4.0	No modification.
Release 3.5.0	No modification.
Release 3.6.0	No modification.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

If the software receives a nonbroadcast packet destined for itself that uses a protocol it does not recognize, it sends an ICMP protocol unreachable message to the source.

If the software receives a datagram that it cannot deliver to its ultimate destination because it knows of no route to the destination address, it replies to the originator of that datagram with an ICMP host unreachable message.

This command affects a number of ICMP unreachable messages.

Task ID

Task ID	Operations
ipv4	read, write
network	read, write

Examples

The following example shows how to disable the generation of ICMP unreachable messages on POS interface 0/1/1/0:

RP/0/RP0/CPU0:router(config)# interface POS 0/1/1/0

RP/0/RP0/CPU0:router(config-if)# ipv4 unreachables disable

ipv4 virtual address

To define an IPv4 virtual address for a network of management Ethernet interfaces, use the ipv4 virtual interface command in global configuration mode. To remove an IPv4 virtual address from the configuration, use the no form of this command.

ipv4 virtual address [vrf vrf-name] {ipv4-address/mask}

no ipv4 virtual address [vrf vrf-name] {ipv4-address/mask}

Syntax Description

vrf vrf-name	(Optional) Configures the virtual address on a per VPN routing and forwarding (VRF) basis for the management interfaces The vrf-name argument specifies the name of the VRF.
ipv4 address	Virtual IPv4 address and the mask that is to be unconfigured.
mask	Mask for the associated IP subnet. The network mask can be specified in either of two ways: •The network mask can be a four-part dotted-decimal address. For example, 255.0.0.0 indicates that each bit equal to 1 means the corresponding address bit belongs to the network address. •The network mask can be indicated as a slash (/) and number. For example, /8 indicates that the first 8 bits of the mask are ones, and the corresponding bits of the address are network address. A slash between numbers is required as part of the notation.

Defaults

No IPv4 virtual address is defined for the configuration.

Command Modes

Global configuration

Command History

Release	Modification
Release 2.0	This command was introduced on the Cisco CRS-1.
Release 3.0	No modification.
Release 3.2	This command was supported on the Cisco XR 12000 Series Router.
Release 3.3.0	No modification.
Release 3.4.0	No modification.
Release 3.5.0	No modification.
Release 3.6.0	The vrf keyword was added to support virtual addresses on a per VRF basis.

Usage Guidelines

To use this command, you must be in a user group associated with a task group that includes the proper task IDs. For detailed information about user groups and task IDs, see the Configuring AAA Services on Cisco IOS XR Software module of the Cisco IOS XR System Security Configuration Guide.

Configuring an IPv4 virtual address enables you to access the router from a single virtual address with a management network. An IPv4 virtual address persists across route processor (RP) failover situations.

Configuring an IPv4 virtual address enables you to access a dual RP router from a single address without prior knowledge of which RP is active. An IPv4 virtual address persists across RP failovers. For this to happen, the virtual IPv4 address must share a common IPv4 subnet with a Management Ethernet interface on both RPs. On a Cisco XR 12000 Series Router in which each RP has multiple Management Ethernet interfaces (two on PRP-1 or three on PRP-2), the virtual IPv4 address maps to whichever Management Ethernet interface on the active RP with which it shares a common IP subnet.

If you disable the ipv4 virtual address command with the vrf keyword, the virtual IP address is unconfigured for the corresponding VRF or for the default if no VRF is specified. This results in the removal of the entry for the virtual IP address in the VRF table and in the ARP cache.

The default VRF is chosen when no VRF is specified. The virtual IP address is activated on a management interface that is attached to a default VRF.

Task ID