Cisco NCS 540 Series User manual

ARP Commands
All commands applicable for the Cisco NCS 5500 Series Router are also supported on the Cisco NCS 540
Series Router that is introduced from Cisco IOS XR Release 6.3.2. References to earlier releases in Command
History tables apply to only the Cisco NCS 5500 Series Router.
Note
This chapter describes the commands used to configure and monitor the Address Resolution Protocol (ARP)
on NCS 5000 routers.
For detailed information about ARP concepts, configuration tasks, and examples, refer to the IP Addresses
and Services Configuration Guide for Cisco NCS 5500 Series Routers.
•arp, on page 1
•arp gratuitous ignore, on page 3
•arp learning, on page 3
•arp purge-delay, on page 4
•arp timeout, on page 5
•clear arp-cache, on page 6
•local-proxy-arp, on page 7
•priority-timeout, on page 8
•proxy-arp, on page 9
•route distance, on page 10
•route metric, on page 11
•show arp, on page 11
•show arp traffic, on page 15
arp
To add a permanent entry in the Address Resolution Protocol (ARP) cache, use the arp command in XR
Config mode. To remove an entry from the ARP cache, enter the no form of this command.
arp [vrf vrf-name]ip-address hardware-address encapsulation-type [alias]
no arp [vrf vrf-name]ip-address hardware-address encapsulation-type [alias]
Syntax Description (Optional) Specifies VPN routing and forwarding (VRF) instance.vrf
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(Optional) VRF instance that identifies a VPN.vrf-name
IPv4 (network layer) address for which a permanent entry is added to the ARP cache.
Enter the IPv4 address in a four-part dotted-decimal format that corresponds to the local
data-link address (a 32-bit address).
ip-address
Hardware (data link layer) address that the IPv4 address is linked to. Enter the local
data-link address (a 48-bit address), such as 0800.0900.1834.
hardware-address
Encapsulation type. The encapsulation types are:
• arpa
• srp
• srpa
• srpb
For Ethernet interfaces, this is typically the arpa keyword.
encapsulation-type
(Optional) Causes the software to respond to ARP requests as if it were the owner of
both the specified IP address and hardware address, whether proxy ARP is enabled or
not.
alias
Command Default No entries are permanently installed in the ARP cache.
Command Modes XR Config mode
Command History ModificationRelease
This command was introduced.Release 6.0
Usage Guidelines The software uses ARP cache entries to translate 32-bit IP addresses into 48-bit hardware addresses.
Because most hosts support dynamic resolution, you generally need not specify static ARP cache entries.
Static entries are permanent entries that map a network layer address (IPv4 address) to a data-link layer address
(MAC address). If the alias keyword is specified when creating the entry, the interface to which the entry
is attached will act as if it is the owner of the specified addresses, that is, it will respond to ARP request packets
for this network layer address with the data link layer address in the entry.
The software does not respond to any ARP requests received for the specified IP address unless proxy ARP
is enabled on the interface on which the request is received. When proxy ARP is enabled, the software responds
to ARP requests with its own local interface hardware address.
To remove all nonstatic entries from the ARP cache, enter the clear arp-cache, on page 6 in XR EXEC mode.
Task ID OperationsTask
ID
read,
write
cef
Examples The following is an example of a static ARP entry for a typical Ethernet host:
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arp

RP/0/RP0/CPU0:router# configure
RP/0/RP0/CPU0:router(config)# arp 192.168.7.19 0800.0900.1834 arpa
arp gratuitous ignore
To ignore receipt of gratuitous Address Resolution Protocol (ARP) packets, use the arp gratuitous ignore
command in interface configuration mode. To receipt gratuitous ARP packets, use the no form of this command.
arp gratuitous ignore
no arp gratuitous ignore
Syntax Description This command has no keywords or arguments.
Command Default Disabled
Command Modes Interface configuration
Command History ModificationRelease
This command was introduced.Release
6.0
Usage Guidelines No specific guidelines impact the use of this command.
Task ID OperationsTask
ID
writecef
Examples This example shows how to configure arp gratuitous ignore command:
RP/0/# configure
RP/0/(config)# interface HundredGigE 0/1/0/0
RP/0/(config-if)# arp gratuitous ignore
arp learning
To enable the dynamic learning of ARP entries for a local subnet or all subnets, use the arp learning command.
To disable this command, use the no prefix or the disable option for this command.
arp learning local
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arp gratuitous ignore

no arp learning local
arp learning disable
no arp learning disable
Syntax Description Enables the dynamic learning of ARP entries for local subnets.
When arp learning local is configured on an interface or sub-interface, it learns only the ARP
entries from ARP packets on the same subnet.
local
Disables the dynamic learning of all ARP entries.disable
Command Default This command has no keywords or arguments.
Command Modes Sub-interface configuration mode
RP/0/RP0/CPU0:router(config)#interface GigabitEthernet 0/0/0/1
RP/0/RP0/CPU0:router(config-if)# ipv4 address 12.1.3.4 255.255.255.0
RP/0/RP0/CPU0:router(config-if)# arp learning local
RP/0/RP0/CPU0:router(config-if)# no shut
RP/0/RP0/CPU0:router(config-if)# commit
RP/0/RP0/CPU0:router(config)# interface GigabitEthernet 0/0/0/1
RP/0/RP0/CPU0:router(config-if)# ipv4 address 12.1.3.4 255.255.255.0
RP/0/RP0/CPU0:router(config-if)# arp learning disable
RP/0/RP0/CPU0:router(config-if)# commit
arp purge-delay
To delay purging Address Resolution Protocol (ARP) entries when an interface goes down, use the arp
purge-delay command in interface configuration mode. To turn off the purge delay feature, use the no form
of this command.
arp purge-delay value
no arp purge-delay value
Syntax Description Sets the purge delay time in seconds. Range is 1 to 65535.value
Command Default Default value is off.
Command Modes Interface configuration
Command History ModificationRelease
This command was introduced.Release 6.0
Usage Guidelines Use the arp purge-delay command to delay purging ARP entries when an interface goes down. If the interface
comes up within the delay time, then the ARP entries are restored to prevent packet loss with Equal Cost
Multipath (ECMP) configured.
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ARP Commands
arp purge-delay

Task ID OperationsTask
ID
read,
write
cef
Examples The following is an example of setting the purge delay to 50 seconds:
RP/0/# configure
RP/0/(config)# interface HundredGigE 0/0/0/0
RP/0/(config-if)# arp purge-delay 50
arp timeout
To specify the duration of dynamic entries learned on an interface remain in the Address Resolution Protocol
(ARP) cache, enter the arp timeout command in interface configuration mode. To remove the arp timeout
command from the configuration file and restore the system to its default condition with respect to this
command, enter the no form of this command.
arp timeout seconds
no arp timeout seconds
Syntax Description Indicates the time, in seconds, for which an entry remains in the ARP cache. Range is 30 to
4294967295.
seconds
Command Default Entries remain in the ARP cache for 14,400 seconds (4 hours).
Command Modes Interface configuration
Command History ModificationRelease
This command was supported.Release 6.0
Usage Guidelines This command is ignored when issued on interfaces that do not use ARP. Also, ARP entries that correspond
to the local interface or that are statically configured by the user never time out.
The arp timeout command applies only to the interface that is entered. When the timeout is changed for an
interface the change applies only to that interface.
The show interfaces command displays the ARP timeout value in hours:minutes:seconds, as follows:
ARP type: ARPA, ARP Timeout 04:00:00
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arp timeout

Task ID OperationsTask
ID
read,
write
cef
Examples The following example shows how to set the ARP timeout to 3600 seconds to allow entries to time
out more quickly than the default:
RP/0/#configure
RP/0/(config)#interface HundredGigE 0/0/0/0
RP/0/(config-if)# arp timeout 3600
clear arp-cache
To delete all dynamic entries from the Address Resolution Protocol (ARP) cache, clear the fast-switching
cache, and clear the IP route cache, use the clear arp-cache command in .
clear arp-cache {traffic type interface-path-id|location node-id}
Syntax Description Deletes traffic statistics on the specified interface.traffic
Interface type. For more information, use the question mark (?) online help function.
t ype
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.
• 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.
interface- path-id
Clears the ARP entries for a specified location. The node-id argument is entered in the
rack/slot/module notation.
location node-id
Command Default No default behavior or values
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clear arp-cache

Command Modes
Command History ModificationRelease
This command was introduced.Release
6.0
Usage Guidelines When issued without keywords or arguments, the clear arp-cache command clears all entries in the ARP
cache.
Task ID OperationsTask
ID
executecef
Examples The following example shows how to remove traffic statistic entries from the ARP cache that match
the specified interface:
RP/0/# clear arp-cache traffic tengige 0/1/0/0 location 0/1/CPU0
The following example shows how to remove entries from the ARP cache that match the specified
location:
RP/0/# clear arp-cache location 0/1/CPU0
local-proxy-arp
To enable local proxy Address Resolution Protocol (ARP) on an interface, enter the local-proxy-arp command
in interface configuration mode. To disable local proxy ARP on the interface, enter the no form of this
command.
local-proxy-arp
no local-proxy-arp
Syntax Description This command has no keywords or arguments.
Command Default Local proxy ARP is disabled on all interfaces.
Command Modes Interface configuration
Command History ModificationRelease
This command was introduced.Release 6.0
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local-proxy-arp

Usage Guidelines When local proxy ARP is enabled, the networking device responds to ARP requests that meet all the following
conditions:
• The target IP address in the ARP request, the IP address of the ARP source, and the IP address of the
interface on which the ARP request is received are on the same Layer 3 network.
• The next hop for the target IP address is through the same interface as the request is received.
Typically, local proxy ARP is used to resolve MAC addresses to IP addresses in the same Layer 3 network
such as, private VLANs that are Layer 2-separated. Local proxy ARP supports all types of interfaces supported
by ARP and unnumbered interfaces.
Using the no form of the command removes the specified command from the configuration file and restores
the system to its default condition with respect to the command.
Task ID OperationsTask
ID
read,
write
cef
priority-timeout
To configure the timer to time out a high-priority Direct Attached Gateway Redundancy (DAGR) route and
reverting to normal priority, use the priority-timeout command in DAGR peer interface configuration mode.
priority-timeout time
Syntax Description Time in seconds after which a high-priority route reverts to a normal priority route. The range of values
is 1 to 10000.
time
Command Default Default for time is 20 seconds.
Command Modes DAGR peer interface configuration
Command History ModificationRelease
This command was introduced.Release 6.0
Usage Guidelines To use this command, you must be in a user group associated with a task group that includes the proper task
IDs. If you suspect user group assignment is preventing you from using a command, contact your AAA
administrator for assistance.
When this function is applied, the DAGR group configuration is updated in the database.
The new timer values take effect the next time the timer is set. No immediate timer restarts are triggered on
the basis of this event.
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ARP Commands
priority-timeout

Task ID OperationsTask
ID
writecef
Examples The following example configures a priority timeout of 25 seconds:
RP/0/(config-if-dagr-peer)# priority-timeout 25
RP/0/(config-if-dagr-peer)#
proxy-arp
To enable proxy Address Resolution Protocol (ARP) on an interface, enter the proxy-arp command in interface
configuration mode. To disable proxy ARP on the interface, enter the no form of this command.
proxy-arp
no proxy-arp
Syntax Description This command has no keywords or arguments.
Command Default Proxy ARP is disabled on all interfaces.
Command Modes Interface configuration
Command History ModificationRelease
This command was introduced.Release 6.0
Usage Guidelines When proxy ARP is disabled, the networking device responds to ARP requests received on an interface only
if one of the following conditions is met:
• The target IP address in the ARP request is the same as the interface IP address on which the request is
received.
• The target IP address in the ARP request has a statically configured ARP alias.
When proxy ARP is enabled, the networking device also responds to ARP requests that meet all of the following
conditions:
• The target IP address is not on the same physical network (LAN) on which the request is received.
• The networking device has one or more routes to the target IP address.
• All of the routes to the target IP address go through interfaces other than the one on which the request
is received.
Using the no form of the command removes the specified command from the configuration file and restores
the system to its default condition with respect to the command.
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proxy-arp

Task ID OperationsTask
ID
read,
write
cef
Examples The following example shows how to enable proxy ARP on HundredGigE interface 0/0/0/0:
RP/0/#(config)# interface HundredGigE 0/0/0/0
RP/0/#(config-if)# proxy-arp
route distance
To configure route distance for a given Direct Attached Gateway Redundancy (DAGR) group, use the route
distance command in DAGR peer interface configuration mode.
route distance normal normal-distance priority priority-distance
Syntax Description Sets normal route (administrative) distance. Range is 0 to 256.
normal normal-distance
Sets priority route (administrative) distance. Range is 0 to 256.
priority priority-distance
Command Default Default for normal-distance default is 150 and the default for priority-distance is 5.
Command Modes DAGR peer interface configuration
Command History ModificationRelease
This command was introduced.Release
6.0
Usage Guidelines The default setting for a priority distance takes precedence over that of a typical Internet Gateway Protocol
(IGP). The normal distance setting does not.
When this setting is applied, the DAGR group is updated in the database.
Task ID OperationsTask
ID
writecef
Examples The following example configures a DAGR group peer with a normal route distance of 48 and priority
route distance of 5:
RP/0/(config-if-dagr-peer)# route distance normal 48 priority 5
RP/0/(config-if-dagr-peer)#
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route distance