Command Reference, Cisco IOS XE Everest 16.5.x (Catalyst 9300 Switches)

clear ip nhrp

To clear all dynamic entries from the Next Hop Resolution Protocol (NHRP) cache, use the clear ip nhrp command in user EXEC or privileged EXEC mode.

clear ip nhrp [vrf {vrf-name | global}] [dest-ip-address [dest-mask] | tunnel number | counters [interface tunnel number] | stats [tunnel number [vrf {vrf-name | global}]]]

Syntax Description


vrf	(Optional) Deletes entries from the NHRP cache for the specified virtual routing and forwarding (VRF) instance.
`vrf-name`	(Optional) Name of the VRF address family to which the command is applied.
global	(Optional) Specifies the global VRF instance.
`dest-ip-address`	(Optional) Destination IP address. Specifying this argument clears NHRP mapping entries for the specified destination IP address.
`dest-mask`	(Optional) Destination network mask.
counters	(Optional) Clears the NHRP counters.
interface	(Optional) Clears the NHRP mapping entries for all interfaces.
tunnel `number`	(Optional) Removes the specified interface from the NHRP cache.
stats	(Optional) Clears all IPv4 statistic information for all interfaces.

Command Modes

User EXEC (>)

Privileged EXEC (#)

Command History


Release	Modification
Cisco IOS XE Denali 16.3.1	This command was introduced.

Usage Guidelines

The clear ip nhrp command does not clear any static (configured) IP-to-NBMA address mappings from the NHRP cache.

Examples

The following example shows how to clear all dynamic entries from the NHRP cache for an interface:


Switch# clear ip nhrp

Related Commands


Command	Description
show ip nhrp	Displays NHRP mapping information.

debug nhrp

To enable Next Hop Resolution Protocol (NHRP) debugging, use the debug nhrp command in privileged EXEC mode. To disable debugging output, use the no form of this command.

debug nhrp [attribute | cache | condition {interface tunnel number | peer {nbma {ipv4-nbma-address| nbma-name | ipv6-nbma-address} } | umatched | vrf vrf-name} | detail | error | extension | group | packet | rate]

no debug nhrp [attribute | cache | condition {interface tunnel number | peer {nbma {ipv4-nbma-address| nbma-name | ipv6-nbma-address} } unmatched | vrf vrf-name} | detail | error | extension | group | packet | rate ]

Syntax Description

attribute

(Optional) Enables NHRP attribute debugging operations.

cache

(Optional) Enables NHRP cache debugging operations.

condition

(Optional) Enables NHRP conditional debugging operations.

interface tunnel number

(Optional) Enables debugging operations for the tunnel interface.

nbma

(Optional) Enables debugging operations for the non-broadcast multiple access (NBMA) network.

ipv4-nbma-address

(Optional) Enables debugging operations based on the IPv4 address of the NBMA network.

nbma-name

(Optional) NBMA network name.

IPv6-address

(Optional) Enables debugging operations based on the IPv6 address of the NBMA network.

Note

The IPv6-address argument is not supported in Cisco IOS XE Denali 16.3.1.

vrf vrf-name

(Optional) Enables debugging operations for the virtual routing and forwarding instance.

detail

(Optional) Displays detailed logs of NHRP debugs.

error

(Optional) Enables NHRP error debugging operations.

extension

(Optional) Enables NHRP extension processing debugging operations.

group

(Optional) Enables NHRP group debugging operations.

packet

(Optional) Enables NHRP activity debugging.

rate

(Optional) Enables NHRP rate limiting.

routing

(Optional) Enables NHRP routing debugging operations.

Command Default

NHRP debugging is not enabled.

Command Modes

Privileged EXEC (#)

Command History


Release	Modification
Cisco IOS XE Denali 16.3.1	This command was introduced.

Usage Guidelines

Note

In Cisco IOS XE Denali 16.3.1, this command supports only IPv4; the IPv6-nbma-address argument although available on the switch, will not work if configured.

Use the debug nhrp detail command to view the NHRP attribute logs.

The Virtual-Access number keyword-argument pair is visible only if the virtual access interface is available on the device.

Examples

The following sample output from the debug nhrp command displays NHRP debugging output for IPv4:


Switch# debug nhrp

Aug  9 13:13:41.486: NHRP: Attempting to send packet via DEST 10.1.1.99
Aug  9 13:13:41.486: NHRP: Encapsulation succeeded.  Tunnel IP addr 10.11.11.99
Aug  9 13:13:41.486: NHRP: Send Registration Request via Tunnel0 vrf 0, packet size: 105
Aug  9 13:13:41.486:       src: 10.1.1.11, dst: 10.1.1.99
Aug  9 13:13:41.486: NHRP: 105 bytes out Tunnel0
Aug  9 13:13:41.486: NHRP: Receive Registration Reply via Tunnel0 vrf 0, packet size: 125
Aug  9 13:13:41.486: NHRP: netid_in = 0, to_us = 1

Related Commands


Command	Description
show ip nhrp	Displays NHRP mapping information.

ip address

To set a primary or secondary IP address for an interface, use the ip address command in interface configuration mode. To remove an IP address or disable IP processing, use the no form of this command.

ip address ip-address mask [secondary [vrf vrf-name]]

no ip address ip-address mask [secondary [vrf vrf-name]]

Syntax Description

ip-address

IP address.

mask

Mask for the associated IP subnet.

secondary

(Optional) Specifies that the configured address is a secondary IP address. If this keyword is omitted, the configured address is the primary IP address.

Note

If the secondary address is used for a VRF table configuration with the vrf keyword, the vrf keyword must be specified also.

vrf

(Optional) Name of the VRF table. The vrf-name argument specifies the VRF name of the ingress interface.

Command Default

No IP address is defined for the interface.

Command Modes

Interface configuration (config-if)

Command History


Release	Modification
	This command was introduced.

Usage Guidelines

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

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

You can disable IP processing on a particular interface by removing its IP address with the no ip address command. If the software detects another host using one of its IP addresses, it will print 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 the system never generates datagrams other than routing updates with secondary source addresses. IP broadcasts and Address Resolution Protocol (ARP) requests are handled properly, as are interface routes in the IP routing table.

Secondary IP 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 300 host addresses. Using secondary IP addresses on the devices or access servers 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, device-based network. Devices on an older, bridged segment can be easily made aware that many subnets are on that segment.
Two subnets of a single network might otherwise be separated by another network. This situation is not permitted when subnets are in use. In these instances, the first network is extended , or layered on top of the second network using secondary addresses.

Note

If any device on a network segment uses a secondary address, all other devices on that same segment must also use a secondary address from the same network or subnet. Inconsistent use of secondary addresses on a network segment can very quickly cause routing loops.
When you are routing using the Open Shortest Path First (OSPF) algorithm, ensure that all secondary addresses of an interface fall into the same OSPF area as the primary addresses.
If you configure a secondary IP address, you must disable sending ICMP redirect messages by entering the no ip redirects command, to avoid high CPU utilization.

Examples

In the following example, 192.108.1.27 is the primary address and 192.31.7.17 is the secondary address for GigabitEthernet interface 1/0/1:

Device# enable 
Device# configure terminal
Device(config)# interface GigabitEthernet 1/0/1
Device(config-if)# ip address 192.108.1.27 255.255.255.0
Device(config-if)# ip address 192.31.7.17 255.255.255.0 secondary

Related Commands


Command	Description
match ip route-source	Specifies a source IP address to match to required route maps that have been set up based on VRF connected routes.
route-map	Defines the conditions for redistributing routes from one routing protocol into another, or to enable policy routing.
set vrf	Enables VPN VRF selection within a route map for policy-based routing VRF selection.
show ip arp	Displays the ARP cache, in which SLIP addresses appear as permanent ARP table entries.
show ip interface	Displays the usability status of interfaces configured for IP.
show route-map	Displays static and dynamic route maps.

ip address dhcp

To acquire an IP address on an interface from the DHCP, use the ip address dhcp command in interface configuration mode. To remove any address that was acquired, use the no form of this command.

ip address dhcp [client-id interface-type number] [hostname hostname]

no ip address dhcp [client-id interface-type number] [hostname hostname]

Syntax Description


client-id	(Optional) Specifies the client identifier. By default, the client identifier is an ASCII value. The client-id `interface-type` `number` option sets the client identifier to the hexadecimal MAC address of the named interface.
`interface-type`	(Optional) Interface type. For more information, use the question mark (?) online help function.
`number`	(Optional) Interface or subinterface number. For more information about the numbering syntax for your networking device, use the question mark (?) online help function.
hostname	(Optional) Specifies the hostname.
`hostname`	(Optional) Name of the host to be placed in the DHCP option 12 field. This name need not be the same as the hostname entered in global configuration mode.

Command Default

The hostname is the globally configured hostname of the device. The client identifier is an ASCII value.

Command Modes

Interface configuration (config-if)

Usage Guidelines

The ip address dhcp command allows any interface to dynamically learn its IP address by using the DHCP protocol. It is especially useful on Ethernet interfaces that dynamically connect to an Internet service provider (ISP). Once assigned a dynamic address, the interface can be used with the Port Address Translation (PAT) of Cisco IOS Network Address Translation (NAT) to provide Internet access to a privately addressed network attached to the device.

The ip address dhcp command also works with ATM point-to-point interfaces and will accept any encapsulation type. However, for ATM multipoint interfaces you must specify Inverse ARP via the protocol ip inarp interface configuration command and use only the aa15snap encapsulation type.

Some ISPs require that the DHCPDISCOVER message have a specific hostname and client identifier that is the MAC address of the interface. The most typical usage of the ip address dhcp client-id interface-type number hostname hostname command is when interface-type is the Ethernet interface where the command is configured and interface-type number is the hostname provided by the ISP.

A client identifier (DHCP option 61) can be a hexadecimal or an ASCII value. By default, the client identifier is an ASCII value. The client-id interface-type number option overrides the default and forces the use of the hexadecimal MAC address of the named interface.

If a Cisco device is configured to obtain its IP address from a DHCP server, it sends a DHCPDISCOVER message to provide information about itself to the DHCP server on the network.

If you use the ip address dhcp command with or without any of the optional keywords, the DHCP option 12 field (hostname option) is included in the DISCOVER message. By default, the hostname specified in option 12 will be the globally configured hostname of the device. However, you can use the ip address dhcp hostname hostname command to place a different name in the DHCP option 12 field than the globally configured hostname of the device.

The no ip address dhcp command removes any IP address that was acquired, thus sending a DHCPRELEASE message.

You might need to experiment with different configurations to determine the one required by your DHCP server. The table below shows the possible configuration methods and the information placed in the DISCOVER message for each method.

Table 1. Configuration Method and Resulting Contents of the DISCOVER Message
Configuration Method	Contents of DISCOVER Messages
ip address dhcp	The DISCOVER message contains “cisco- `mac-address` -Eth1” in the client ID field. The `mac-address` is the MAC address of the Ethernet 1 interface and contains the default hostname of the device in the option 12 field.
ip address dhcp hostname `hostname`	The DISCOVER message contains “cisco- `mac-address` -Eth1” in the client ID field. The `mac-address` is the MAC address of the Ethernet 1 interface, and contains `hostname` in the option 12 field.
ip address dhcp client-id ethernet 1	The DISCOVER message contains the MAC address of the Ethernet 1 interface in the client ID field and contains the default hostname of the device in the option 12 field.
ip address dhcp client-id ethernet 1 hostname `hostname`	The DISCOVER message contains the MAC address of the Ethernet 1 interface in the client ID field and contains `hostname` in the option 12 field.

Examples

In the examples that follow, the command ip address dhcp is entered for Ethernet interface 1. The DISCOVER message sent by a device configured as shown in the following example would contain “cisco- mac-address -Eth1” in the client-ID field, and the value abc in the option 12 field.


hostname abc
!
interface GigabitEthernet 1/0/1
 ip address dhcp

The DISCOVER message sent by a device configured as shown in the following example would contain “cisco- mac-address -Eth1” in the client-ID field, and the value def in the option 12 field.


hostname abc
!
interface GigabitEthernet 1/0/1
 ip address dhcp hostname def

The DISCOVER message sent by a device configured as shown in the following example would contain the MAC address of Ethernet interface 1 in the client-id field, and the value abc in the option 12 field.


hostname abc
!
interface Ethernet 1
 ip address dhcp client-id GigabitEthernet 1/0/1

The DISCOVER message sent by a device configured as shown in the following example would contain the MAC address of Ethernet interface 1 in the client-id field, and the value def in the option 12 field.


hostname abc
!
interface Ethernet 1
 ip address dhcp client-id GigabitEthernet 1/0/1 hostname def

Related Commands


Command	Description
ip dhcp pool	Configures a DHCP address pool on a Cisco IOS DHCP server and enters DHCP pool configuration mode.

ip address pool (DHCP)

To enable the IP address of an interface to be automatically configured when a Dynamic Host Configuration Protocol (DHCP) pool is populated with a subnet from IP Control Protocol (IPCP) negotiation, use the ip address pool command in interface configuration mode. To disable autoconfiguring of the IP address of the interface, use the no form of this command.

ip address pool name

no ip address pool

Syntax Description


`name`	Name of the DHCP pool. The IP address of the interface will be automatically configured from the DHCP pool specified in `name` .

Command Default

IP address pooling is disabled.

Command Modes

Interface configuration

Usage Guidelines

Use this command to automatically configure the IP address of a LAN interface when there are DHCP clients on the attached LAN that should be serviced by the DHCP pool on the device. The DHCP pool obtains its subnet dynamically through IPCP subnet negotiation.

Examples

The following example specifies that the IP address of GigabitEthernet interface 1/0/1 will be automatically configured from the address pool named abc:


ip dhcp pool abc
  import all
  origin ipcp
!
interface GigabitEthernet 1/0/1
  ip address pool abc

Related Commands


Command	Description
show ip interface	Displays the usability status of interfaces configured for IP.

ip nhrp map

To statically configure the IP-to-nonbroadcast multiaccess (NBMA) address mapping of IP destinations connected to an NBMA network, use the ip nhrp map command in interface configuration mode. To remove the static entry from Next Hop Resolution Protocol (NHRP) cache, use the no form of this command.

ip nhrp map ip-address {ip-nbma-address | destination-mask [ip-nbma-address | ipv6-nbma-address] | ipv6-nbma-address}

no ip nhrp map ip-address {ip-nbma-address | destination-mask [ip-nbma-address | ipv6-nbma-address] | ipv6-nbma-address}

Syntax Description

ip-address

IP address of the destinations reachable through the NBMA network. This address is mapped to the NBMA address.

ip-nbma-address

NBMA address that is directly reachable through the NBMA network. The address format varies depending on the medium; for example, ATM has a Network Service Access Point (NSAP) address, Ethernet has a MAC address, and Switched Multimegabit Data Service (SMDS) has an E.164 address. This address is mapped to the IP address.

destination-mask

Destination address mask.

ipv6-nbma-address

IPv6 NBMA address.

Note

This argument is not supported in Cisco IOS XE Denali 16.3.1.

Command Default

No static IP-to-NBMA cache entries exist.

Command Modes

Interface configuration(config-if)

Command History


Release	Modification
Cisco IOS XE Denali 16.3.1	This command was introduced.

Usage Guidelines

In Cisco IOS XE Denali 16.3.1, NHRP supports only hub-to-spoke communication; spoke-to-spoke communication is not supported.

Note

In Cisco IOS XE Denali 16.3.1, this command supports only IPv4; the ipv6-nbma-address argument although available on the switch, will not work if configured.

Configure at least one static mapping to reach the next-hop server. To statistically configure multiple IP-to-NBMA address mappings, configure this command multiple times.

When using the routing protocols, Open Shortest Path First (OSPF) or Enhanced Interior Gateway Routing Protocol (EIGRP), configure the ip ospf network point-to-multipoint (when OSPF is used for hub-to-spoke communication) and ip split-horizon eigrp (when EIGRP is used) commands on the tunnel to allow the traffic.

Examples

In the following example, this station in a multipoint tunnel network is statically configured to be served by two next-hop servers 10.0.0.1 and 10.0.1.3. The NBMA address for 10.0.0.1 is statically configured as 192.0.2.1 and the NBMA address for 10.0.1.3 is 198.51.100.1.


Switch(config)# interface tunnel 0
Switch(config-if)# ip nhrp nhs 10.0.0.1
Switch(config-if)# ip nhrp nhs 10.0.1.3
Switch(config-if)# ip nhrp map 10.0.0.1 192.0.2.1
Switch(config-if)# ip nhrp map 10.0.1.3 198.51.100.1

Related Commands


Command	Description
clear ip nhrp	Clears all dynamic entries from the NHRP cache.
debug nhrp	Enables NHRP debugging.
interface	Configures an interface and enters interface configuration mode.
ip split-horizon eigrp	Enables EIGRP split horizon.
ip ospf network point-to-multipoint	Configures the OSPF network type to point-to-multipoint.

ip nhrp map multicast

To configure nonbroadcast multiaccess (NBMA) addresses used as destinations for broadcast or multicast packets to be sent over a tunnel network, use the ip nhrp map multicast command in interface configuration mode. To remove the destinations, use the no form of this command.

ip nhrp map multicast {ip-nbma-address| ipv6-nbma-address | dynamic}

no ip nhrp map multicast {ip-nbma-address| ipv6-nbma-address | dynamic}

Syntax Description

ip-nbma-address

NBMA address that is directly reachable through the NBMA network. The address format varies depending on the medium that you are using.

ipv6-nbma-address

IPv6 NBMA address.

Note

This argument is not supported in Cisco IOS XE Denali 16.3.1.

dynamic

Dynamically learns destinations from client registrations on the hub.

Command Default

No NBMA addresses are configured as destinations for broadcast or multicast packets.

Command Modes

Interface configuration (config-if)

Command History


Release	Modification
Cisco IOS XE Denali 16.3.1	This command was introduced.

Usage Guidelines

Note

In Cisco IOS XE Denali 16.3.1, this command supports only IPv4; the ipv6-nbma-address argument although available on the switch, will not work if configured.

This command applies only to tunnel interfaces. This command is useful for supporting broadcasts over a tunnel network when the underlying network does not support IP multicast. If the underlying network does support IP multicast, you should use the tunnel destination command to configure a multicast destination for transmission of tunnel broadcasts or multicasts.

When multiple NBMA addresses are configured, the system replicates the broadcast packet for each address.

Examples

In the following example, if a packet is sent to 10.255.255.255, it is replicated to destinations 10.0.0.1 and 10.0.0.2:


Switch(config)# interface tunnel 0
Switch(config-if)# ip address 10.0.0.3 255.0.0.0
Switch(config-if)# ip nhrp map multicast 10.0.0.1
Switch(config-if)# ip nhrp map multicast 10.0.0.2

Related Commands


Command	Description
debug nhrp	Enables NHRP debugging.
interface	Configures an interface and enters interface configuration mode.
tunnel destination	Specifies the destination for a tunnel interface.

ip nhrp network-id

To enable the Next Hop Resolution Protocol (NHRP) on an interface, use the ip nhrp network-id command in interface configuration mode. To disable NHRP on the interface, use the no form of this command.

ip nhrp network-id number

no ip nhrp network-id [number]

Syntax Description


`number`	Globally unique, 32-bit network identifier from a nonbroadcast multiaccess (NBMA) network. The range is from 1 to 4294967295.

Command Default

NHRP is disabled on an interface.

Command Modes

Interface configuration (config)

Command History


Release	Modification
Cisco IOS XE Denali 16.3.1	This command was introduced.

Usage Guidelines

In general, all NHRP stations within one logical NBMA network must be configured with the same network identifier.

Examples

The following example enables NHRP on the interface:


Switch(config-if)# ip nhrp network-id 1

Related Commands


Command	Description
clear ip nhrp	Clears all dynamic entries from the NHRP cache.
debug nhrp	Enables NHRP debugging.
interface	Configures an interface and enters interface configuration mode.

ip nhrp nhs

To specify the address of one or more Next Hop Resolution Protocol (NHRP) servers, use the ip nhrp nhs command in interface configuration mode. To remove the address, use the no form of this command.

ip nhrp nhs {nhs-address [nbma {nbma-address | FQDN-string}] [multicast] [priority value] [cluster value] | cluster value max-connections value | dynamic nbma {nbma-address | FQDN-string} [multicast] [priority value] [cluster value] | fallback seconds}

no ip nhrp nhs {nhs-address [nbma {nbma-address | FQDN-string}] [multicast] [priority value] [cluster value] | cluster value max-connections value | dynamic nbma {nbma-address | FQDN-string} [multicast] [priority value] [cluster value] | fallback seconds}

Syntax Description


`nhs-address`	Address of the next-hop server being specified.
nbma	(Optional) Specifies the nonbroadcast multiple access (NBMA) address or FQDN.
`nbma-address`	NBMA address.
`FQDN-string`	Next hop server (NHS) fully qualified domain name (FQDN) string.
multicast	(Optional) Specifies the use of NBMA mapping for broadcasts and multicasts.
priority `value`	(Optional) Assigns a priority to hubs to control the order in which spokes select hubs to establish tunnels. The range is from 0 to 255; 0 is the highest and 255 is the lowest priority.
cluster `value`	(Optional) Specifies NHS groups. The range is from 0 to 10.
max-connections `value`	Specifies the number of NHS elements from each NHS group that needs to be active. The range is from 0 to 255.
dynamic	Configures the spoke to learn the NHS protocol address dynamically.
fallback `seconds`	Specifies the duration, in seconds, for which the spoke must wait before falling back to an NHS of higher priority upon recovery.

Command Default

No next-hop servers are explicitly configured, so normal network layer routing decisions are used to forward NHRP traffic.

Command Modes

Interface configuration (config-if)

Command History


Release	Modification
Cisco IOS XE Denali 16.3.1	This command was introduced.

Usage Guidelines

Use the ip nhrp nhs command to specify the address of a next hop server and the networks it serves. Normally, NHRP consults the network layer forwarding table to determine how to forward NHRP packets. When next hop servers are configured, these next hop addresses override the forwarding path that would otherwise be used for NHRP traffic.

For any next hop server that is configured, you can specify multiple networks by repeating the ip nhrp nhs command with the same nhs-address argument, but with different IP network addresses.

Examples

The following example shows how to register a hub to a spoke using NBMA and FQDN:


Switch# configure terminal
Switch(config)# interface tunnel 1
Switch(config-if)# ip nhrp nhs 192.0.2.1 nbma examplehub.example1.com

The following example shows how to configure the desired max-connections value:


Switch# configure terminal
Switch(config)# interface tunnel 1
Switch(config-if)# ip nhrp nhs cluster 5 max-connections 100

The following example shows how to configure the NHS fallback time:


Switch# configure terminal
Switch(config)# interface tunnel 1
Switch(config-if)# ip nhrp nhs fallback 25

The following example shows how to configure NHS priority and group values:


Switch# configure terminal
Switch(config)# interface tunnel 1
Switch(config-if)# ip nhrp nhs 192.0.2.1 priority 1 cluster 2

Related Commands


Command	Description
ip nhrp map	Statically configures the IP-to-NBMA address mapping of IP destinations connected to an NBMA network.
show ip nhrp	Displays NHRP mapping information.

ipv6 nd cache expire

To configure the duration of time before an IPv6 neighbor discovery cache entry expires, use the ipv6 nd cache expire command in the interface configuration mode. To remove this configuration, use the no form of this command.

ipv6 nd cache expire expire-time-in-seconds [refresh]

no ipv6 nd cache expire expire-time-in-seconds [refresh]

Syntax Description


`expire-time-in-seconds`	The time range is from 1 through 65536 seconds. The default is 14400 seconds or 4 hours.
refresh	(Optional) Automatically refreshes the neighbor discovery cache entry.

Command Modes

Interface configuration (config-if)

Command History


Release	Modification
	This command was introduced.

Usage Guidelines

By default, a neighbor discovery cache entry is expired and deleted if it remains in the STALE state for 14,400 seconds or 4 hours. The ipv6 nd cache expire command allows the expiry time to vary and to trigger auto refresh of an expired entry before the entry is deleted.

When the refresh keyword is used, a neighbor discovery cache entry is auto refreshed. The entry moves into the DELAY state and the neighbor unreachability detection process occurs, in which the entry transitions from the DELAY state to the PROBE state after 5 seconds. When the entry reaches the PROBE state, a neighbor solicitation is sent and then retransmitted as per the configuration.

Examples

The following example shows that the neighbor discovery cache entry is configured to expire in 7200 seconds or 2 hours:

Device> enable
Device# configure terminal
Device(config)# interface gigabitethernet 1/1/4
Device(config-if)# ipv6 nd cache expire 7200

Related Commands


Command	Description
ipv6 nd na glean	Configures neighbor discovery to glean an entry from an unsolicited neighbor advertisement.
ipv6 nd nud retry	Configures the number of times neighbor unreachability detection resends neighbor solicitations.
show ipv6 interface	Displays the usability status of interfaces that are configured for IPv6.

ipv6 nd na glean

To configure the neighbor discovery to glean an entry from an unsolicited neighbor advertisement, use the ipv6 nd na glean command in the interface configuration mode. To disable this feature, use the no form of this command.

ipv6 nd na glean

no ipv6 nd na glean

Command Modes

Interface configuration

Command History


Release	Modification
	This command was introduced.

Usage Guidelines

IPv6 nodes may emit a multicast unsolicited neighbor advertisement packet following the successful completion of duplicate address detection (DAD). By default, other IPv6 nodes ignore these unsolicited neighbor advertisement packets. The ipv6 nd na glean command configures the router to create a neighbor advertisement entry on receipt of an unsolicited neighbor advertisement packet (assuming no such entry already exists and the neighbor advertisement has the link-layer address option). Use of this command allows a device to populate its neighbor advertisement cache with an entry for a neighbor before data traffic exchange with the neighbor.

Examples

The following example shows how to configure neighbor discovery to glean an entry from an unsolicited neighbor advertisement:

Device> enable
Device# configure terminal
Device(config)# interface gigabitethernet 1/1/4
Device(config-if)# ipv6 nd na glean

Related Commands


Command	Description
ipv6 nd cache expire	Configures the duration of time before an IPv6 neighbor discovery cache entry expires.
ipv6 nd nud retry	Configures the number of times neighbor unreachability detection resends neighbor solicitations.
show ipv6 interface	Displays the usability status of interfaces that are configured for IPv6.

ipv6 nd nud retry

To configure the number of times the neighbor unreachability detection process resends neighbor solicitations, use the ipv6 nd nud retry command in the interface configuration mode. To disable this feature, use the no form of this command.

ipv6 nd nud retry base interval max-attempts {final-wait-time}

no ipv6 nd nud retry base interval max-attempts {final-wait-time}

Syntax Description


`base`	The neighbor unreachability detection process base value.
`interval`	The time interval, in milliseconds, between retries. The range is from 1000 to 32000.
`max-attempts`	The maximum number of retry attempts, depending on the base value. The range is from 1 to 128.
`final-wait-time`	The waiting time, in milliseconds, on the last probe. The range is from 1000 to 32000.

Command Modes

Interface configuration (config-if)

Command History


Release	Modification
	This command was introduced.

Usage Guidelines

When a device runs neighbor unreachability detection to resolve the neighbor detection entry for a neighbor again, it sends three neighbor solicitation packets 1 second apart. In certain situations, for example, spanning-tree events, or high-traffic events, or end-host reloads), three neighbor solicitation packets that are sent at an interval of 1 second may not be sufficient. To help maintain the neighbor cache in such situations, use the ipv6 nd nud retry command to configure exponential timers for neighbor solicitation retransmits.

The maximum number of retry attempts is configured using the max-attempts argument. The retransmit interval is calculated with the following formula:

tm^n

here,

t = Time interval
m = Base (1, 2, or 3)
n = Current neighbor solicitation number (where the first neighbor solicitation is 0).

Therefore, ipv6 nd nud retry 3 1000 5 command retransmits at intervals of 1,3,9,27,81 seconds. If the final wait time is not configured, the entry remains for 243 seconds before it is deleted.

The ipv6 nd nud retry command affects only the retransmit rate for the neighbor unreachability detection process, and not for the initial resolution, which uses the default of three neighbor solicitation packets sent 1 second apart.

Examples

The following example shows how to configure a fixed interval of 1 second and three retransmits:

Device> enable
Device# configure terminal
Device(config)# interface gigabitethernet 1/1/4
Device(config-if)# ipv6 nd nud retry 1 1000 3

The following example shows how to configure a retransmit interval of 1, 2, 4, and 8:

Device> enable
Device# configure terminal
Device(config)# interface gigabitethernet 1/1/4
Device(config-if)# ipv6 nd nud retry 2 1000 4

The following example shows how to configure the retransmit intervals of 1, 3, 9, 27, 81:

Device> enable
Device# configure terminal
Device(config)# interface gigabitethernet 1/1/4
Device(config-if)# ipv6 nd nud retry 3 1000 5

Related Commands


Command	Description
ipv6 nd cache expire	Configures the duration of time before an IPv6 neighbor discovery (ND) cache entry expires.
ipv6 nd na glean	Configures neighbor discovery to glean an entry from an unsolicited neighbor advertisement.
show ipv6 interface	Displays the usability status of interfaces that are configured for IPv6.

show ip nhrp nhs

To display Next Hop Resolution Protocol (NHRP) next hop server (NHS) information, use the show ip nhrp nhs command in user EXEC or privileged EXEC mode.

show ip nhrp nhs [interface] [detail] [redundancy [cluster number | preempted | running | waiting]]

Syntax Description


`interface`	(Optional) Displays NHS information currently configured on the interface. See the table below for types, number ranges, and descriptions.
detail	(Optional) Displays detailed NHS information.
redundancy	(Optional) Displays information about NHS redundancy stacks.
cluster `number`	(Optional) Displays redundancy cluster information.
preempted	(Optional) Displays information about NHS that failed to become active and is preempted.
running	(Optional) Displays NHSs that are currently in Responding or Expecting replies states.
waiting	(Optional) Displays NHSs awaiting to be scheduled.

Command Modes

User EXEC (>)

Privileged EXEC (#)

Command History


Release	Modification
Cisco IOS XE Denali 16.3.1	This command was introduced.

Usage Guidelines

The table below lists the valid types, number ranges, and descriptions for the optional interface argument.

Note

The valid types can vary according to the platform and interfaces on the platform.

Table 2. Valid Types, Number Ranges, and Interface Descriptions
Valid Types	Number Ranges	Interface Descriptions
ANI	0 to 1000	Autonomic-Networking virtual interface
Auto-Template	1 to 999	Auto-Template interface
Capwap	0 to 2147483647	Control and Provisioning of Wireless Access Points protocol (CAPWAP) tunnel interface
GMPLS	0 to 1000	Multiprotocol Label Switching (MPLS) interface
GigabitEthernet	0 to 9	GigabitEthernet IEEE 802.3z
InternalInterface	0 to 9	Internal interface
LISP	0 to 65520	Locator/ID Separation Protocol (LISP) virtual interface
loopback	0 to 2147483647	Loopback interface
Null	0 to 0	Null interface
PROTECTION_GROUP	0 to 0	Protection-group controller
Port-channel	1 to 128	Port channel interface
TenGigabitEthernet	0 to 9	TenGigabitEthernet interface
Tunnel	0 to 2147483647	Tunnel interface
Tunnel-tp	0 to 65535	MPLS Transport Profile interface
Vlan	1 to 4094	VLAN interface

Examples

The following is sample output from the show ip nhrp nhs detail command:


Switch# show ip nhrp nhs detail

Legend:
  E=Expecting replies
  R=Responding
Tunnel1:
  	10.1.1.1           E  req-sent 128  req-failed 1  repl-recv 0
Pending Registration Requests:
Registration Request: Reqid 1, Ret 64  NHS 10.1.1.1

The table below describes the significant field shown in the display.

Table 3. show ip nhrp nhs Field Descriptions
Field	Description
Tunnel1	Interface through which the target network is reached.

Related Commands


Command	Description
ip nhrp map	Statically configures the IP-to-NBMA address mapping of IP destinations connected to an NBMA network.
show ip nhrp	Displays NHRP mapping information.

show track

To display information about objects that are tracked by the tracking process, use the show track command in privileged EXEC mode.

Syntax Description


`object-number`	(Optional) Object number that represents the object to be tracked. The range is from 1 to 1000.
brief	(Optional) Displays a single line of information related to the preceding argument or keyword.
application	(Optional) Displays tracked application objects.
interface	(Optional) Displays tracked interface objects.
ip route	(Optional) Displays tracked IP route objects.
ip sla	(Optional) Displays tracked IP SLA objects.
ipv6 route	(Optional) Displays tracked IPv6 route objects.
list	(Optional) Displays the list of boolean objects.
resolution	(Optional) Displays resolution of tracked parameters.
summary	(Optional) Displays the summary of the specified object.
timers	(Optional) Displays polling interval timers.

Command Modes

Privileged EXEC (#)

Command History


Release	Modification
	This command was introduced.

Usage Guidelines

Use this command to display information about objects that are tracked by the tracking process. When no arguments or keywords are specified, information for all objects is displayed.

A maximum of 1000 objects can be tracked. Although 1000 tracked objects can be configured, each tracked object uses CPU resources. The amount of available CPU resources on a device is dependent upon variables such as traffic load and how other protocols are configured and run. The ability to use 1000 tracked objects is dependent upon the available CPU. Testing should be conducted on site to ensure that the service works under the specific site traffic conditions.

Examples

The following example shows information about the state of IP routing on the interface that is being tracked:


Device# show track 1

Track 1
 Interface GigabitEthernet 1/0/1 ip routing
 IP routing is Down (no IP addr)
  1 change, last change 00:01:08

The table below describes the significant fields shown in the displays.

Table 4. show track Field Descriptions
Field	Description
Track	Object number that is being tracked.
Interface GigabitEthernet 1/0/1 ip routing	Interface type, interface number, and object that is being tracked.
IP routing is	State value of the object, displayed as Up or Down. If the object is down, the reason is displayed.
1 change, last change	Number of times that the state of a tracked object has changed and the time (in hh:mm:ss ) since the last change.

Related Commands


Command	Description
show track resolution	Displays the resolution of tracked parameters.
track interface	Configures an interface to be tracked and enters tracking configuration mode.
track ip route	Tracks the state of an IP route and enters tracking configuration mode.

track

To configure an interface to be tracked where the Gateway Load Balancing Protocol (GLBP) weighting changes based on the state of the interface, use the track command in global configuration mode. To remove the tracking, use the no form of this command.

track object-number interface type number {line-protocol | ip routing|ipv6 routing}

no track object-number interface type number {line-protocol | ip routing|ipv6 routing}

Syntax Description


`object-number`	Object number in the range from 1 to 1000 representing the interface to be tracked.
interface `type` `number`	Interface type and number to be tracked.
line-protocol	Tracks whether the interface is up.
ip routing	Tracks whether IP routing is enabled, an IP address is configured on the interface, and the interface state is up, before reporting to GLBP that the interface is up.
ipv6 routing	Tracks whether IPv6 routing is enabled, an IP address is configured on the interface, and the interface state is up, before reporting to GLBP that the interface is up.

Command Default

The state of the interfaces is not tracked.

Command Modes

Global configuration (config)

Command History


Release	Modification
	This command was introduced..

Usage Guidelines

Use the track command in conjunction with the glbp weighting and glbp weighting track commands to configure parameters for an interface to be tracked. If a tracked interface on a GLBP device goes down, the weighting for that device is reduced. If the weighting falls below a specified minimum, the device will lose its ability to act as an active GLBP virtual forwarder.

A maximum of 1000 objects can be tracked. Although 1000 tracked objects can be configured, each tracked object uses CPU resources. The amount of available CPU resources on a device is dependent upon variables such as traffic load and how other protocols are configured and run. The ability to use 1000 tracked objects is dependent upon the available CPU. Testing should be conducted on site to ensure that the service works under the specific site traffic conditions.

Examples

In the following example, TenGigabitEthernet interface 0/0/1 tracks whether GigabitEthernet interfaces 1/0/1 and 1/0/3 are up. If either of the GigabitEthernet interface goes down, the GLBP weighting is reduced by the default value of 10. If both GigabitEthernet interfaces go down, the GLBP weighting will fall below the lower threshold and the device will no longer be an active forwarder. To resume its role as an active forwarder, the device must have both tracked interfaces back up, and the weighting must rise above the upper threshold.


Device(config)# track 1 interface GigabitEthernet 1/0/1 line-protocol 
Device(config-track)# exit
Device(config)# track 2 interface GigabitEthernet 1/0/3 line-protocol 
Device(config-track)# exit
Device(config)# interface TenGigabitEthernet 0/0/1 
Device(config-if)# ip address 10.21.8.32 255.255.255.0 
Device(config-if)# glbp 10 weighting 110 lower 95 upper 105 
Device(config-if)# glbp 10 weighting track 1
Device(config-if)# glbp 10 weighting track 2

Related Commands


Command	Description
glbp weighting	Specifies the initial weighting value of a GLBP gateway.
glbp weighting track	Specifies an object to be tracked that affects the weighting of a GLBP gateway.

Bias-Free Language

Results

Chapter: IP Commands

IP Commands

clear ip nhrp

Syntax Description

Command Modes

Command History

Usage Guidelines

Examples

Related Commands

debug nhrp

Syntax Description

Command Default

Command Modes

Command History

Usage Guidelines

Examples

Related Commands

ip address

Syntax Description

Command Default

Command Modes

Command History

Usage Guidelines

Examples

Related Commands

ip address dhcp

Syntax Description

Command Default

Command Modes

Usage Guidelines

Examples

Related Commands

ip address pool (DHCP)

Syntax Description

Command Default

Command Modes

Usage Guidelines

Examples

Related Commands

ip nhrp map

Syntax Description

Command Default

Command Modes

Command History

Usage Guidelines

Examples

Related Commands

ip nhrp map multicast

Syntax Description

Command Default

Command Modes

Command History

Usage Guidelines

Examples

Related Commands

ip nhrp network-id

Syntax Description

Command Default

Command Modes

Command History

Usage Guidelines

Examples

Related Commands

ip nhrp nhs

Syntax Description

Command Default

Command Modes

Command History

Usage Guidelines

Examples

Related Commands

ipv6 nd cache expire

Syntax Description

Syntax Description

Command Modes

Command History

Usage Guidelines