Configuring ARP
783
When Host A and Host B are not on the same subnet, Host A first sends an ARP
request to the gateway. The destination IP address in the ARP request is the IP
address of the gateway. After obtaining the MAC address of the gateway from an
ARP reply, Host A encapsulates the packet and sends it to the gateway.
Subsequently, the gateway broadcasts the ARP request, in which the destination IP
address is the one of Host B. After obtaining the MAC address of Host B from
another ARP reply, the gateway sends the packet to Host B.
ARP Mapping Table
After obtaining the destination MAC address, the device adds the IP-to-MAC
mapping into its own ARP mapping table. This mapping is used for forwarding
packets with the same destination in future.
An ARP mapping table contains ARP entries, which fall into two categories:
dynamic and static.
1
A dynamic entry is automatically created and maintained by ARP. It can get aged,
be updated by a new ARP packet, or be overwritten by a static ARP entry. When
the aging timer expires or the port goes down, the corresponding dynamic ARP
entry will be removed.
2
A static ARP entry is manually configured and maintained. It cannot get aged or be
overwritten by a dynamic ARP entry. It can be permanent or non-permanent.
■
A permanent static ARP entry can be directly used to forward packets. When
configuring a permanent static ARP entry, you must configure a VLAN and
outbound port for the entry besides the IP address and MAC address.
■
A non-permanent static ARP entry cannot be directly used for forwarding data.
When configuring a non-permanent static ARP entry, you only need to
configure the IP address and MAC address. When forwarding IP packets, the
device sends an ARP request. If the source IP and MAC addresses in the
received ARP reply are the same as the configured IP and MAC addresses, the
device adds the port receiving the ARP reply into the static ARP entry. Now the
entry can be used for forwarding IP packets.
n
Usually ARP dynamically implements and automatically seeks mappings from IP
addresses to MAC addresses, without manual intervention.
Configuring ARP
Configuring a Static ARP
Entry
A static ARP entry is effective when the device works normally. However, when a
VLAN or VLAN interface to which a static ARP entry corresponds is deleted, the
entry, if permanent, will be deleted, and if non-permanent and resolved, will
become unresolved.
Follow these steps to configure a static ARP entry:
To do…
Use the command…
Remarks
Enter system view
system-view
-
Configure a permanent static
ARP entry
arp static
ip-address
mac-address vlan-id
interface-type
interface-number
Required
No permanent static ARP
entry is configured by default.
Summary of Contents for 4800G Series
Page 26: ...26 CHAPTER NETWORKING APPLICATIONS ...
Page 30: ...30 CHAPTER 1 LOGGING IN TO AN ETHERNET SWITCH ...
Page 62: ...62 CHAPTER 3 LOGGING IN THROUGH TELNET ...
Page 70: ...70 CHAPTER 5 LOGGING IN THROUGH WEB BASED NETWORK MANAGEMENT SYSTEM ...
Page 72: ...72 CHAPTER 6 LOGGING IN THROUGH NMS ...
Page 82: ...82 CHAPTER 8 CONTROLLING LOGIN USERS ...
Page 98: ...98 CHAPTER 9 VLAN CONFIGURATION ...
Page 108: ...108 CHAPTER 10 VOICE VLAN CONFIGURATION ...
Page 119: ...GVRP Configuration Examples 119 DeviceB display vlan dynamic No dynamic vlans exist ...
Page 120: ...120 CHAPTER 11 GVRP CONFIGURATION ...
Page 160: ...160 CHAPTER 17 PORT ISOLATION CONFIGURATION ...
Page 172: ...172 CHAPTER 19 LINK AGGREGATION CONFIGURATION ...
Page 196: ...196 CHAPTER 22 DLDP CONFIGURATION ...
Page 240: ...240 CHAPTER 23 MSTP CONFIGURATION ...
Page 272: ...272 CHAPTER 27 RIP CONFIGURATION ...
Page 364: ...364 CHAPTER 29 IS IS CONFIGURATION ...
Page 426: ...426 CHAPTER 31 ROUTING POLICY CONFIGURATION ...
Page 442: ...442 CHAPTER 33 IPV6 RIPNG CONFIGURATION ...
Page 466: ...466 CHAPTER 35 IPV6 IS IS CONFIGURATION ...
Page 488: ...488 CHAPTER 36 IPV6 BGP CONFIGURATION ...
Page 498: ...498 CHAPTER 37 ROUTING POLICY CONFIGURATION ...
Page 540: ...540 CHAPTER 40 TUNNELING CONFIGURATION ...
Page 552: ...552 CHAPTER 41 MULTICAST OVERVIEW ...
Page 604: ...604 CHAPTER 43 MLD SNOOPING CONFIGURATION ...
Page 628: ...628 CHAPTER 46 IGMP CONFIGURATION ...
Page 700: ...700 CHAPTER 48 MSDP CONFIGURATION ...
Page 812: ...812 CHAPTER 57 DHCP SERVER CONFIGURATION ...
Page 822: ...822 CHAPTER 58 DHCP RELAY AGENT CONFIGURATION ...
Page 834: ...834 CHAPTER 61 BOOTP CLIENT CONFIGURATION ...
Page 850: ...850 CHAPTER 63 IPV4 ACL CONFIGURATION ...
Page 856: ...856 CHAPTER 64 IPV6 ACL CONFIGURATION ...
Page 860: ...860 CHAPTER 65 QOS OVERVIEW ...
Page 868: ...868 CHAPTER 66 TRAFFIC CLASSIFICATION TP AND LR CONFIGURATION ...
Page 888: ...888 CHAPTER 69 PRIORITY MAPPING ...
Page 894: ...894 CHAPTER 71 TRAFFIC MIRRORING CONFIGURATION ...
Page 904: ...904 CHAPTER 72 PORT MIRRORING CONFIGURATION ...
Page 930: ...930 CHAPTER 74 UDP HELPER CONFIGURATION ...
Page 990: ...990 CHAPTER 79 FILE SYSTEM MANAGEMENT CONFIGURATION ...
Page 1000: ...1000 CHAPTER 80 FTP CONFIGURATION ...
Page 1020: ...1020 CHAPTER 82 INFORMATION CENTER CONFIGURATION ...
Page 1038: ...1038 CHAPTER 84 SYSTEM MAINTAINING AND DEBUGGING ...
Page 1046: ...1046 CHAPTER 85 DEVICE MANAGEMENT ...
Page 1129: ...SSH Client Configuration Examples 1129 SwitchB ...
Page 1130: ...1130 CHAPTER 88 SSH CONFIGURATION ...
Page 1160: ...1160 CHAPTER 90 RRPP CONFIGURATION ...
Page 1180: ...1180 CHAPTER 91 PORT SECURITY CONFIGURATION ...
Page 1192: ...1192 CHAPTER 92 LLDP CONFIGURATION ...
Page 1202: ...1202 CHAPTER 93 POE CONFIGURATION ...
Page 1218: ...1218 CHAPTER 96 HTTPS CONFIGURATION ...