Cisco WS-C2980G-A Software Guide - Page 416

Configuring Permanent and Static ARP Entries

Page 416 highlights

Configuring Permanent and Static ARP Entries Chapter 27 Administering the Switch This example shows how to define two IP aliases, sparc, which refers to IP address 172.20.52.3, and cat4003, which refers to IP address 172.20.52.71. This example also shows how to verify the currently defined IP aliases: Console> (enable) set ip alias sparc 172.20.52.3 IP alias added. Console> (enable) set ip alias cat4003 172.20.52.71 IP alias added. This example shows what happens when you use the IP aliases with the ping command: Console> (enable) show ip alias default 0.0.0.0 sparc 172.20.52.3 cat5509 172.20.52.71 Console> (enable) ping sparc sparc is alive Console> (enable) ping cat4003 cat4003 is alive Console> (enable) Configuring Permanent and Static ARP Entries To enable your Catalyst LAN switch to communicate with devices that do not respond to Address Resolution Protocol (ARP) requests, you can configure a static or permanent ARP entry that maps the IP addresses of those devices to their MAC addresses. You can configure an ARP entry so that it does not age out, by configuring it as either static or permanent. When you configure a static ARP entry using the set arp static command, the entry is removed from the ARP cache after a system reset. When you configure a permanent ARP by using the set arp permanent command, the ARP entry is retained even after a system reset. Because most hosts support dynamic resolution, you usually do not need to specify static or permanent ARP cache entries. When a device does not respond to ARP requests, you can configure an ARP entry to be statically or permanently entered into the ARP cache so that those devices can still be reached. To configure a static or permanent ARP entry, perform this task in privileged mode: Step 1 Step 2 Step 3 Task Command Configure a static or permanent ARP entry. set arp [dynamic | permanent | static] {ip_addr hw_addr} (Optional) Specify the ARP aging time. set arp agingtime seconds Verify the ARP configuration. show arp This example shows how to define a static ARP entry: Console> (enable) set arp static 20.1.1.1 00-80-1c-93-80-40 Static ARP entry added as 20.1.1.1 at 00-80-1c-93-80-40 on vlan 1 Console> (enable) This example shows how to define a permanent ARP entry: Console> (enable) set arp permanent 10.1.1.1 00-80-1c-93-80-60 Permanent ARP entry added as 10.1.1.1 at 00-80-1c-93-80-60 on vlan 1 Console> (enable) 27-8 Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide-Release 8.1 78-15486-01

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27-8
Catalyst 4500 Series, Catalyst 2948G, Catalyst 2980G Switches Software Configuration Guide
Release 8.1
78-15486-01
Chapter 27
Administering the Switch
Configuring Permanent and Static ARP Entries
This example shows how to define two IP aliases,
sparc
, which refers to IP address 172.20.52.3, and
cat4003
, which refers to IP address 172.20.52.71. This example also shows how to verify the currently
defined IP aliases:
Console> (enable)
set ip alias sparc 172.20.52.3
IP alias added.
Console> (enable)
set ip alias cat4003 172.20.52.71
IP alias added.
This example shows what happens when you use the IP aliases with the
ping
command:
Console> (enable)
show ip alias
default
0.0.0.0
sparc
172.20.52.3
cat5509
172.20.52.71
Console> (enable)
ping sparc
sparc is alive
Console> (enable)
ping cat4003
cat4003 is alive
Console> (enable)
Configuring Permanent and Static ARP Entries
To enable your Catalyst LAN switch to communicate with devices that do not respond to Address
Resolution Protocol (ARP) requests, you can configure a static or permanent ARP entry that maps the
IP addresses of those devices to their MAC addresses. You can configure an ARP entry so that it does
not age out, by configuring it as either static or permanent. When you configure a static ARP entry using
the
set arp static
command, the entry is removed from the ARP cache after a system reset. When you
configure a permanent ARP by using the
set arp permanent
command, the ARP entry is retained even
after a system reset.
Because most hosts support dynamic resolution, you usually do not need to specify static or permanent
ARP cache entries. When a device does not respond to ARP requests, you can configure an ARP entry
to be statically or permanently entered into the ARP cache so that those devices can still be reached.
To configure a static or permanent ARP entry, perform this task in privileged mode:
This example shows how to define a static ARP entry:
Console> (enable)
set arp static 20.1.1.1 00-80-1c-93-80-40
Static ARP entry added as 20.1.1.1 at 00-80-1c-93-80-40 on vlan 1
Console> (enable)
This example shows how to define a permanent ARP entry:
Console> (enable)
set arp permanent 10.1.1.1 00-80-1c-93-80-60
Permanent ARP entry added as
10.1.1.1
at 00-80-1c-93-80-60 on vlan 1
Console> (enable)
Task
Command
Step 1
Configure a static or permanent ARP entry.
set arp
[
dynamic
|
permanent
|
static
] {
ip_addr
hw_addr
}
Step 2
(Optional) Specify the ARP aging time.
set arp agingtime
seconds
Step 3
Verify the ARP configuration.
show arp