4.1. ARP Commands

Command Purpose

To add a permanent entry in the Address Resolution Protocol (ARP) cache, use the arp command in Global Config mode.

To remove an entry from the ARP cache, use the no form of this command.

Prerequisites

Command Syntax

arp ( vrf VRF-NAME | ) IP-ADDRESS HARDWARE-ADDRESS

no arp ( vrf VRF-NAME | ) IP-ADDRESS

Command Mode

Global Config

Default

No entries are permanently installed in the ARP cache.

Usage

Because most hosts support dynamic resolution, you generally need not specify static ARP cache entries.

To remove all none static entries from the ARP cache, use the clear arp-cache privileged EXEC command.

Examples

The following is an example of add a static ARP entry for a typical Ethernet host:

Switch# configure terminal
Switch(config)# arp 10.31.7.19 0058.3f00.1834

Related Commands

clear arp-cache

Command Purpose

When an interface requests a mapping for an address not in the cache, system will send ARP request message on the associated network requesting the address mapping. Usually, 3 request messages will be sent until the system got a response. To configure the ARP request delay interval between 2 messages, use arp retry-interval command in interface configuration mode. To restore the default value, use the no form of this command.

Prerequisites

Command Syntax

arp retry-interval SECONDS

no arp retry-interval

Command Mode

Interface Configuration

Default

1 second

Usage

This command is ignored when issued on interfaces that do not use ARP. The show interface EXEC command displays the ARP retry interval value. The value as seen in the following example from the show interface command:

ARP timeout 01:00:00, ARP retry interval 1s

Examples

The following example sets the ARP retry interval to 3 seconds:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# no switchport
Switch(config-if)# arp retry-interval 3

Related Commands

show interface

Command Purpose

Use this command to set the arp timeout value. Use the no form of this command to restore the default value.

Prerequisites

Command Syntax

arp timeout SECONDS

no arp timeout

Command Mode

Interface Configuration

Default

3600 seconds (1 hour)

Usage

This command is ignored when issued on interfaces that do not use ARP. The show interface EXEC command displays the ARP timeout value. The value as seen in the following example from the show interface command:

ARP timeout 01:00:00, ARP retry interval 1s

Examples

The following example sets the ARP timeout to 1200 seconds to allow entries to time out more quickly than the default:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# no switchport
Switch(config-if)# arp timeout 1200

Related Commands

show interface

Command Purpose

To set that deal with the arp packet as layer3 packet. To disable arp as-layer-3, use the no form of this command.

Prerequisites

Command Syntax

arp as-layer-3 enable

no arp as-layer-3 enable

Command Mode

Global Config

Default

Disable

Usage

vlan classifier and IGMP Snooping affected by the CLI.

Enable, vlan classifier activate base ip, the arp packet matched source ip address will classifier to specified vlan. Otherwise, not classifier to specified vlan.

Enable, ip source guard enable the ip check on the port, the arp packet matched source ip address will not filter. Ohterwise, will filter.

Examples

The following example show how to enable arp as-layer-3:

Switch# configure terminal
Switch(config)# arp as-layer-3 enable

Related Commands

N/A

Command Purpose

To enable fake arp global, use the no form of this command.To disable arp fake global, use the no form of this command.

Prerequisites

Command Syntax

arp fake global enable

no arp fake global enable

Command Mode

Global Config

Default

Disable

Usage

Not effect until both enable global and interface arp fake.

Examples

The following example show how to enable global fake arp:

Switch# configure terminal
Switch(config)# arp fake global enable

Related Commands

arp fake enable

Command Purpose

To enable fake arp on interface, use the no form of this command.

Prerequisites

Command Syntax

arp fake enable

no arp fake enable

Command Mode

Interface Configuration

Default

Enable

Usage

If enable, the interface receive IP packets that not match any ARP entry will create an fake ARP entry. Before interface received ARP reply, the IP packets matched the fake ARP entry will be dropped. After interface received ARP reply, will create active ARP entry instead of fake ARP entry.

Examples

The following example show how to enable fake arp:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# arp fake enable

Related Commands

arp fake global enable

Command Purpose

To configure how long a fake entry remains in the ARP cache, use the arp fake timeout command in interface configuration mode. To restore the default value, use the no form of this command.

Prerequisites

Command Syntax

arp fake timeout SECONDS

no arp fake timeout

Command Mode

Interface Configuration

Default

5 seconds

Usage

When switch was attached, can let the fake ARP entry to time out later.

Examples

The following example sets the ARP fake timeout to 100 seconds to allow entries to time out:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# arp fake timeout 100

Related Commands

N/A

Command Purpose

To refresh dynamically created entries from the Address Resolution Protocol (ARP) cache, use the clear arp-cache command in privileged EXEC mode.

Prerequisites

Command Syntax

clear arp-cache ( ( vrf VRF-NAME | ) interface IFNAME | )

Command Mode

Privileged EXEC

Default

No default behavior or values.

Usage

This command updates the dynamically learned IP address and MAC address mapping information in the ARP table to ensure the validity of those entries. If the refresh operation encounters any stale entries (dynamic ARP entries that have expired but have not yet been aged out by an internal, timer-driven process), those entries are aged out of the ARP table immediately as opposed to at the next refresh interval.

Use this command without any arguments or keywords to refresh all ARP cache entries for all enabled interfaces.

Examples

The following example shows how to refresh all dynamically learned ARP cache entries for all enabled interfaces:

Switch# clear arp-cache

Related Commands

show ip arp

Command Purpose

To refresh the specific dynamically created entry from the Address Resolution Protocol (ARP) cache, use the clear ip arp command in privileged EXEC mode.

Prerequisites

Command Syntax

clear ip arp ( vrf VRF-NAME | ) IP-ADDRESS

Command Mode

Privileged EXEC

Default

No default behavior or values.

Usage

This command updates the specific dynamically learned IP address and MAC address mapping information in the ARP table. If the refresh operation encounters any stale entries (dynamic ARP entries that have expired but have not yet been aged out by an internal, timer-driven process), the entry is aged out of the ARP table immediately as opposed to at the next refresh interval.

Examples

The following example shows how to refresh the dynamically learned ARP entries 10.10.10.10:

Switch# clear ip arp 10.10.10.10

Related Commands

show ip arp

Command Purpose

To clear ARP packets statistics processed by system, use the clear ip arp statistics command in privileged EXEC mode.

Prerequisites

Command Syntax

clear ip arp ( vrf VRF-NAME | ) statistics

Command Mode

Privileged EXEC

Default

No default behavior or values.

Usage

This command use to clear ARP packets statistics.

Examples

The following example shows how to clear ARP packets statistcs:

Switch# clear ip arp statistics

Related Commands

show ip arp summary

Command Purpose

To display the entries in the Address Resolution Protocol (ARP) table, use the show ip arp command in privileged EXEC mode.

Prerequisites

Command Syntax

show ip arp ( ( vrf VRF-NAME | ) interface INTERFACE-NAME | )

Command Mode

Privileged EXEC

Default

None

Usage

To display all entries in the ARP cache, use this command without any arguments or keywords.

Examples

The following is sample output from the show ip arp command:

Switch# show ip arp

Protocol Address Age (min) Hardware Addr Interface
Internet 1.1.1.1 - 0058.3f57.0c00 eth-0-1
Internet 2.2.2.1 - 0058.3f57.0c00 eth-0-2
Internet 3.3.3.1 - 0058.3f57.0c00 eth-0-3
Internet 10.0.20.1 - 0058.3f57.0c00 eth-0-10
Internet 10.0.20.254 - 0058.3f00.0101 eth-0-10

Related Commands

clear ip arp

Command Purpose

To display the total number of Address Resolution Protocol (ARP) table entries, the number of ARP table entries for each ARP entry mode, and the number of ARP table entries for each interface on the router, use the show ip arp summary command in privileged EXEC mode.

Prerequisites

Command Syntax

show ip arp ( vrf VRF-NAME | ) summary

Command Mode

Privileged EXEC

Default

None

Usage

Use this command to display high-level statistics about the ARP table entries:

Examples

The following is sample output from the show ip arp summary command:

Switch# show ip arp summary

Gratuitous ARP learning is disabled
2 IP ARP entries, with 0 of them incomplete
(Static:1, Dyamic:0, Interface:1)
ARP Pkt Received is: 0
ARP Pkt Send number is: 1
ARP Pkt Dicard number is: 0

Related Commands

clear ip arp statistics

Command Purpose

To turn on the ARP debug, use debugs arp command in EXEC mode. To turn off the ARP debug, use the no form of this command.

Prerequisites

Command Syntax

debug arp ( vrf VRF-NAME | )

Command Mode

Privileged EXEC

Default

None

Usage

Use this command to debug ARP packets received and send; also for debug ARP entry creating, updating and deleting.

Examples

The following is sample output from the debug arp command:

Switch# debug arp

Sep  7 03:34:08 SWITCH ARP-7: IP ARP: creating entry for IP address: 7.7.7.7, hw: e64d。0445。df00 
Sep  7 03:34:08 SWITCH ARP-7: IP ARP: send req src 7.7.7.7 e64d。0445。df00, dst 7.7.7.7 eth-0-1

Related Commands

show debugging arp

Command Purpose

To display the debugging status of ARP, use the show debugging arp command in EXEC mode.

Prerequisites

Command Syntax

show debugging arp ( vrf VRF-NAME | )

Command Mode

Privileged EXEC

Default

None

Usage

Use this command to display the debugging status of ARP.

Examples

The following is sample output from the show debugging arp command:

Switch# show debugging arp

ARP debugging status:
ARP packet debugging is on

Related Commands

debug arp

Command Purpose

The switch uses proxy ARP to help hosts determine MAC addresses of hosts on other networks or subnets.

To enable proxy Address Resolution Protocol (ARP) on an interface, use the proxy-arp enable command in interface configuration mode. To disable proxy ARP on the interface, use the no form of this command.

Prerequisites

Command Syntax

proxy-arp enable

Command Mode

Interface Configuration

Default

Proxy ARP is disabled by default.

Usage

When proxy ARP is disabled, a device will respond to ARP requests received on its interface only if the target IP address is the same as its IP address.

Examples

The following example enables proxy ARP on interface eth-0-1:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# no switchport
Switch(config-if)# no shutdown
Switch(config-if)#ip address 1.1.1.1/24
Switch(config-if)# proxy-arp enable

Related Commands

local-proxy-arp enable

Command Purpose

The local proxy ARP feature allow the L3 Device to response ARP request whose ARP Target address is in the same subnet the as the ARP request comes from (No Routing is required).

To enable local proxy Address Resolution Protocol (ARP) on an interface, use the local-proxy-arp enable command in interface configuration mode.

To disable proxy ARP on the interface, use the no form of this command.

Prerequisites

Command Syntax

local-proxy-arp enable

no local-proxy-arp enable

Command Mode

Interface Configuration

Default

Local proxy ARP is disabled by default.

Usage

Internet Control Message Protocol (ICMP) redirects are disabled on interfaces when the local proxy ARP feature is enabled. The main condition we need to enable local ARP proxy is that the switch enables port isolate.

Examples

The following example enables local proxy ARP on interface eth-0-1:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# no switchport
Switch(config-if)# no shutdown
Switch(config-if)# ip address 1.1.1.1/24
Switch(config-if)# local-proxy-arp enable

Related Commands

proxy-arp enable

Command Purpose

To enable the gratuitous Address Resolution Protocol (ARP) control on the router, use the gratuitous-arp-learning enable command in Global Config mode. To disable the ARP control, use the no form of this command.

Prerequisites

Command Syntax

gratuitous-arp-learning enable

no gratuitous-arp-learning enable

Command Mode

Global Config

Default

Gratuitous ARP learning is disabled by default.

Usage

None

Examples

The following example enables gratuitous ARP learning on interface eth-0-1:

Switch# configure terminal
Switch(config)# gratuitous-arp-learning enable

Related Commands

show ip arp summary

Command Purpose

To config the gratuitous ARP send interval, use the no form of this command to recover to default.

Prerequisites

Command Syntax

arp gratuitous-arp send interval SECONDS

no arp gratuitous-arp send interval

Command Mode

Interface Configuration

Default

60 seconds

Usage

None

Examples

The following example config gratuitous ARP send interval on interface eth-0-1:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# no switchport
Switch(config-if)# no shutdown
Switch(config-if)#ip address 1.1.1.1/24
Switch(config-if)#arp gratuitous-arp send interval 80

Related Commands

arp gratuitous-arp send enable

Command Purpose

To enable the gratuitous ARP send on the interface.

Prerequisites

Command Syntax

arp gratuitous-arp send enable

no arp gratuitous-arp send enable

Command Mode

Interface Configuration

Default

disbale

Usage

None

Examples

The following example enable gratuitous ARP oninterface eth-0-1:

Switch# configure terminal
Switch(config)# interface eth-0-1
Switch(config-if)# no switchport
Switch(config-if)# no shutdown
Switch(config-if)#ip address 1.1.1.1/24
Switch(config-if)#arp gratuitous-arp send enable

Related Commands

arp gratuitous-arp send interval