I Commands
This chapter describes the Cisco NX-OS Layer 3 interfaces commands that begin with I.
ip address
To set a primary or secondary IP address for an interface, use the ip address command. To remove an IP address or disable IP processing, use the no form of this command.
ip address ip-address mask [ secondary ]
no ip address ip-address mask [ secondary ]
Syntax Description
Command Default
Command Modes
Interface configuration mode
Subinterface configuration mode
Command History
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Usage Guidelines
Note
Before you use this command, make sure that you use the no switchport command on the interface to use the Layer 3 features.
An interface can have one primary IP address and one secondary IP address.
You can disable IP processing on a particular interface by removing its IP address with the no ip address command.
The optional secondary keyword allows you to specify a secondary IP address. 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, as are interface routes in the IP routing table.
Note When you are routing using the Open Shortest Path First (OSPF) algorithm, ensure that the secondary address of an interface fall into the same OSPF area as the primary addresses.
Examples
This example shows how to configure the IP address 192.168.0.27 as the primary address and 192.168.0.5 as the secondary address for Ethernet interface 1/5:
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Saves the configuration change to the startup configuration file. |
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ip arp
To configure a static Address Resolution Protocol (ARP) entry, use the ip arp command. To remove a static ARP entry, use the no form of this command.
Syntax Description
Command Default
Command Modes
Command HistoryInterface configuration mode
Subinterface configuration mode
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Usage Guidelines
Use this command on Layer 3 interfaces and Layer 3 subinterfaces.
Examples
This example shows how to configure a static ARP entry on interface Ethernet 1/2:
This example shows how to configure a static ARP entry on a subinterface:
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ip arp gratuitous
To enable gratuitous Address Resolution Protocol (ARP), use the ip arp gratuitous command. To disable gratuitous ARP, use the no form of this command.
ip arp gratuitous { request | update }
no ip arp gratuitous { request | update }
Syntax Description
Enables sending gratuitous ARP requests when a duplicate address is detected. |
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Command Default
Command Modes
Command History
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Examples
This example shows how to disable gratuitous ARP request on interface Ethernet 2/1:
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ip arp timeout
To configure an Address Resolution Protocol (ARP) timeout, use the ip arp timeout command. To revert to the default value, use the no form of this command.
Syntax Description
Time (in seconds) that an entry remains in the ARP cache. Valid values are from 60 to 28800, and the default is 1500. |
Command Default
Command Modes
Command History
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Examples
This example shows how to configure the ARP timeout value to 120 seconds:
This example shows how to revert to the default ARP timeout value of 1500 seconds:
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Displays the ARP configuration, including the default configurations. |
ip directed-broadcast
To enable the translation of a directed broadcast to physical broadcasts, use the ip directed-broadcast command. To disable this function, use the no form of this command.
Syntax Description
Command Default
Command Modes
Subinterface configuration mode
Command History
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Usage Guidelines
An IP directed broadcast is an IP packet whose destination address is a valid broadcast address for some IP subnet but which originates from a node that is not itself part of that destination subnet.
A device that is not directly connected to its destination subnet forwards an IP directed broadcast in the same way it would forward unicast IP packets destined to a host on that subnet. When a directed broadcast packet reaches a device that is directly connected to its destination subnet, that packet is broadcast on the destination subnet. The destination address in the IP header of the packet is rewritten to the configured IP broadcast address for the subnet, and the packet is sent as a link-layer broadcast.
If directed broadcast is enabled for an interface, incoming IP packets whose addresses identify them as directed broadcasts intended for the subnet to which that interface is attached are broadcast on that subnet.
If the no ip directed-broadcast command has been configured for an interface, directed broadcasts destined for the subnet to which that interface is attached are dropped, rather than being broadcast.
Note Because directed broadcasts, and particularly Internet Control Message Protocol (ICMP) directed broadcasts, have been abused by malicious persons, we recommend that you disable the ip directed-broadcast command on any interface where directed broadcasts are not needed. We also recommend that you use access lists to limit the number of broadcast packets.
Examples
This example shows how to enable forwarding of IP directed broadcasts on Ethernet interface 2/1:
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interface ethernet (Layer 3)
To configure a Layer 3 Ethernet IEEE 802.3 routed interface, use the interface ethernet command.
interface ethernet [ chassis_ID /] slot /[ QSFP-module /] port [. subintf-port-no ]
Syntax Description
Command Default
Command Modes
Global configuration mode
Interface configuration mode
Command History
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Usage Guidelines
You must use the no switchport command in the interface configuration mode to configure the interface as a Layer 3 routed interface. When you configure the interface as a Layer 3 interface, all Layer 2 specific configurations on this interface are deleted.
Use the switchport command to convert a Layer 3 interface into a Layer 2 interface. When you configure the interface as a Layer 2 interface, all Layer 3 specific configurations on this interface are deleted.
Examples
This example shows how to enter configuration mode for a Layer 3 Ethernet interface 1/5:
switch(config)# interface ethernet 1/5
switch(config-if)# no switchport
switch(config-if)# ip address 10.1.1.1/24
switch(config-if)#
This example shows how to enter configuration mode for a host interface on a Fabric Extender:
switch(config)# interface ethernet 101/1/1
switch(config-if)# no switchport
switch(config-if)# ip address 10.1.1.1/24
switch(config-if)#
This example shows how to configure a Layer 3 subinterface for Ethernet interface 1/5 in the global configuration mode:
switch(config)# interface ethernet 1/5.2
switch(config-if)# no switchport
switch(config-subif)# ip address 10.1.1.1/24
switch(config-subif)#
This example shows how to configure a Layer 3 subinterface in interface configuration mode:
switch(config)# interface ethernet 1/5
switch(config-if)# interface ethernet 1/5.1
switch(config-subif)# ip address 10.1.1.1/24
switch(config-subif)#
This example shows how to convert a Layer 3 interface to a Layer 2 interface:
switch(config)# interface ethernet 1/5
switch(config-if)# no switchport
switch(config-if)# ip address 10.1.1.1/24
switch(config-if)# switchport
switch(config-if)#
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Displays all configured Fabric Extender chassis connected to the switch. |
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Displays various parameters of an Ethernet IEEE 802.3 interface. |
ip local-proxy-arp
To enable the local proxy Address Resolution Protocol (ARP) feature, use the ip local-proxy-arp command. To disable this feature, use the no form of this command.
Syntax Description
Command Default
Command Modes
Interface configuration mode
Subinterface configuration mode
Command History
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Usage Guidelines
Before the local proxy ARP feature can be used, you must enable the IP proxy ARP feature by using the ip proxy-arp command. The IP proxy ARP feature is disabled by default.
Note This command is not applicable to Layer 3 loopback interfaces.
Examples
This example shows how to enable the local proxy ARP:
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interface loopback
To create a loopback interface and enter interface configuration mode, use the interface loopback command. To remove a loopback interface, use the no form of this command.
Syntax Description
Command Default
Command Modes
Command History
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Usage Guidelines
Use the interface loopback command to create or modify loopback interfaces.
From the loopback interface configuration mode, the following parameters are available:
- description —Provides a description of the purpose of the interface.
- ip —Configures IP features, such as the IP address for the interface, Address Resolution Protocol (ARP) attributes, load balancing, Unicast Reverse Path Forwarding (RPF) or IP Source Guard.
- logging —Configure logging of events.
- shutdown —Shut down traffic on the interface.
Examples
This example shows how to create a loopback interface:
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Displays information about the traffic on the specified loopback interface. |
interface port-channel
To create an EtherChannel interface and enter interface configuration mode, use the interface port-channel command. To remove an EtherChannel interface, use the no form of this command.
interface port-channel channel-number [. subintf-channel-no ]
no interface port-channel channel-number [. subintf-channel-no ]
Syntax Description
Channel number that is assigned to this EtherChannel logical interface. The range is from 1 to 4096. |
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(Optional) Port number of the EtherChannel subinterface. The range is from 1 to 4093. |
Command Default
Command Modes
Global configuration mode
Interface configuration mode
Command History
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Usage Guidelines
A port can belong to only one channel group.
When you use the interface port-channel command for Layer 2 interfaces, follow these guidelines:
- If you are using CDP, you must configure it only on the physical interface and not on the EtherChannel interface.
- If you do not assign a static MAC address on the EtherChannel interface, a MAC address is automatically assigned. If you assign a static MAC address and then later remove it, the MAC address is automatically assigned.
- The MAC address of the EtherChannel is the address of the first operational port added to the channel group. If this first-added port is removed from the channel, the MAC address comes from the next operational port added, if there is one.
You must use the no switchport command in the interface configuration mode to configure the EtherChannel interface as a Layer 3 interface. When you configure the interface as a Layer 3 interface, all Layer 2 specific configurations on this interface are deleted.
Use the switchport command to convert a Layer 3 EtherChannel interface into a Layer 2 interface. When you configure the interface as a Layer 2 interface, all Layer 3 specific configurations on this interface are deleted.
You can configure one or more subinterfaces on a port channel made from routed interfaces.
Examples
This example shows how to create an EtherChannel group interface with channel-group number 50:
This example shows how to create a Layer 3 EtherChannel group interface with channel-group number 10:
This example shows how to configure a Layer 3 EtherChannel subinterface with channel-group number 1 in interface configuration mode:
This example shows how to configure a Layer 3 EtherChannel subinterface with channel-group number 20.1 in global configuration mode:
Related Commands
ip port-unreachable
To enable the generation of Internet Control Message Protocol (ICMP) port unreachable messages, use the ip port-unreachable command. To disable this function, use the no form of this command.
Syntax Description
Command Default
Command Modes
Subinterface configuration mode
Command History
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Examples
This example shows how to enable the generation of ICMP port unreachable messages, as appropriate, on an interface:
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ip proxy-arp
To enable proxy Address Resolution Protocol (ARP) on an interface, use the ip proxy-arp command. To disable proxy ARP on the interface, use the no form of this command.
Syntax Description
Command Default
Command Modes
Subinterface configuration mode
Command History
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Examples
This example shows how to enable proxy ARP:
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ip tcp path-mtu-discovery
To enable path maximum transmission unit (MTU) discovery on an IPv4 interface, use the ip tcp path-mtu discovery command. To disable this feature, use the no form of this command.
Syntax Description
Command Default
Command Modes
Command History
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Examples
This example shows how to enable path MTU discovery for IPv4:
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ip tcp synwait-time
To set a period of time the Cisco NX-OS software waits while attempting to establish a TCP connection before it times out, use the ip tcp synwait-time command. To restore the default time, use the no form of this command.
Syntax Description
Time, in seconds, the software waits while attempting to establish a TCP connection. It can be an integer from 5 to 300 seconds. |
Command Default
Command Modes
Command History
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Usage Guidelines
Examples
This example shows how to configure the switch software to continue attempting to establish a TCP connection for 10 seconds:
This example shows how to disable TCP synchronization on interfaces:
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ip unreachables
To enable the generation of Internet Control Message Protocol (ICMP) unreachable messages, use the ip unreachables command. To disable this function, use the no form of this command.
Syntax Description
Command Default
Command Modes
Subinterface configuration mode
Command History
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Examples
This example shows how to enable the generation of ICMP unreachable messages on an interface:
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ipv6 nd
To configure IPv6 neighbor discovery (ND), use the ipv6 nd command. To remove the IPv6 ND configuration, use the no form of this command.
ipv6 nd {hop-limit hop-limit | managed-config-flag | mtu | ns-interval ns-interval | other-config-flag | prefix {A:B::C:D/LEN | default {0-4294967295 | infinite {infinite [no-autoconfig | no-onlink | off-link]}| no-advertise}} | ra-interval ra-interval | ra-lifetime ra-lifetime | reachable-time reachable-time | redirects | retrans-timer retrans-timer | suppress-ra [mtu]}
no ipv6 nd {hop-limit hop-limit | managed-config-flag | mtu mtu-size | ns-interval ns-interval | other-config-flag | prefix {A:B::C:D/LEN | default {0-4294967295 | infinite {infinite [no-autoconfig | no-onlink | off-link]}| no-advertise}} | ra-interval ra-interval | ra-lifetime ra-lifetime | reachable-time reachable-time | redirects | retrans-timer retrans-timer | suppress-ra [mtu]}
Syntax Description
Defaults
hop-limit–64
mtu–1500
ns-interval–1000
ra-interval–600
reachable-time–0
retrans-timer–0
Command Modes
Command History
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Usage Guidelines
Examples
This example shows how to configure IPv6 neighbor discovery:
This example shows how to remove IPv6 neighbor discovery:
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