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C
HAPTER
16
| IP Configuration
Address Resolution Protocol
– 487 –
traffic passes along the path to its final destination in this way, with each
routing device mapping the destination IP address to the MAC address of
the next hop toward the recipient, until the packet is delivered to the final
destination.
If there is no entry for an IP address in the ARP cache, the switch will
broadcast an ARP request packet to all devices on the network. The ARP
request contains the following fields similar to that shown in this example:
When devices receive this request, they discard it if their address does not
match the destination IP address in the message. However, if it does
match, they write their own hardware address into the destination MAC
address field and send the message back to the source hardware address.
When the source device receives a reply, it writes the destination IP
address and corresponding MAC address into its cache, and forwards the IP
traffic on to the next hop. As long as this entry has not timed out, the
switch will be able forward traffic directly to the next hop for this
destination without having to broadcast another ARP request.
Also, if the switch receives a request for its own IP address, it will send
back a response, and also cache the MAC of the source device's IP address.
S
ETTING
THE
ARP
T
IMEOUT
Use the IP > ARP (Configure General) page to specify the timeout for ARP
cache entries.
CLI R
EFERENCES
P
ARAMETERS
These parameters are displayed:
Timeout
– Sets the aging time for dynamic entries in the ARP cache.
(Range: 300 - 86400 seconds; Default: 1200 seconds or 20 minutes)
The ARP aging timeout can only be set globally for all VLANs.
The aging time determines how long dynamic entries remain in the
cache. If the timeout is too short, the switch may tie up resources by
repeating ARP requests for addresses recently flushed from the table.
When a ARP entry expires, it is deleted from the cache and an ARP
request packet is sent to re-establish the MAC address.
Table 35: Address Resolution Protocol
destination IP address
10.1.0.19
destination MAC address ?
source IP address
10.1.0.253
source MAC address
00-00-ab-cd-00-00
Summary of Contents for DG-FS4526E
Page 4: ...ABOUT THIS GUIDE 4...
Page 34: ...CONTENTS 34...
Page 50: ...TABLES 50...
Page 52: ...SECTION I Getting Started 52...
Page 62: ...CHAPTER 1 Introduction System Defaults 62...
Page 80: ...CHAPTER 2 Initial Switch Configuration Managing System Files 80...
Page 82: ...SECTION II Web Configuration 82...
Page 100: ...CHAPTER 3 Using the Web Interface Navigating the Web Browser Interface 100...
Page 128: ...CHAPTER 4 Basic Management Tasks Resetting the System 128...
Page 166: ...CHAPTER 5 Interface Configuration VLAN Trunking 166...
Page 198: ...CHAPTER 6 VLAN Configuration Configuring VLAN Mirroring 198...
Page 516: ...CHAPTER 17 IP Services Displaying the DNS Cache 516...
Page 562: ...CHAPTER 19 Using the Command Line Interface CLI Command Groups 562...
Page 652: ...CHAPTER 22 SNMP Commands 652...
Page 660: ...CHAPTER 23 Remote Monitoring Commands 660...
Page 714: ...CHAPTER 24 Authentication Commands Management IP Filter 714...
Page 802: ...CHAPTER 27 Interface Commands 802...
Page 824: ...CHAPTER 29 Port Mirroring Commands RSPAN Mirroring Commands 824...
Page 846: ...CHAPTER 32 Address Table Commands 846...
Page 874: ...CHAPTER 33 Spanning Tree Commands 874...
Page 886: ...CHAPTER 34 ERPS Commands 886...
Page 928: ...CHAPTER 35 VLAN Commands Configuring Voice VLANs 928...
Page 942: ...CHAPTER 36 Class of Service Commands Priority Commands Layer 3 and 4 942...
Page 998: ...CHAPTER 38 Multicast Filtering Commands Multicast VLAN Registration 998...
Page 1022: ...CHAPTER 39 LLDP Commands 1022...
Page 1064: ...CHAPTER 40 CFM Commands 1064...
Page 1084: ...CHAPTER 42 Domain Name Service Commands 1084...
Page 1090: ...CHAPTER 43 DHCP Commands DHCP Client 1090...
Page 1122: ...CHAPTER 44 IP Interface Commands IPv6 Interface 1122...
Page 1124: ...SECTION IV Appendices 1124...
Page 1130: ...APPENDIX A Software Specifications Management Information Bases 1130...
Page 1152: ...COMMAND LIST 1152...
Page 1161: ......
Page 1162: ...DG FS4526E 042012 HW R01...