GS2210 Series User’s Guide
349
C
H A P T E R
4 1
ARP Setup
41.1 ARP Overview
Addr ess Resolut ion Pr ot ocol ( ARP) is a pr ot ocol for m apping an I nt er net Pr ot ocol addr ess ( I P
addr ess) t o a physical m achine addr ess, also know n as a Media Access Cont r ol or MAC addr ess, on
t he local area net w ork.
An I P ( ver sion 4) address is 32 bit s long. I n an Et hernet LAN, MAC addr esses are 48 bit s long. The
ARP t able m aint ains an associat ion bet w een each MAC addr ess and it s cor r esponding I P addr ess.
41.1.1 What You Can Do
Use t he ARP Le a r n in g scr een (
) t o configur e ARP lear ning m ode on a
per - port basis.
41.1.2 What You Need to Know
Read on for concept s on ARP t hat can help you configur e t he scr een in t his chapt er.
41.1.2.1 How ARP Works
When an incom ing packet dest ined for a host device on a local ar ea net w or k ar r ives at t he Sw it ch,
t he Swit ch looks in t he ARP Table and if it finds t he addr ess, it sends it t o t he device.
I f no ent r y is found for t he I P addr ess, ARP br oadcast s t he r equest t o all t he devices on t he LAN.
The Swit ch fills in it s ow n MAC and I P addr ess in t he sender addr ess fields, and put s t he know n I P
addr ess of t he t ar get in t he t ar get I P addr ess field. I n addit ion, t he Swit ch put s all ones in t he
t ar get MAC field ( FF.FF.FF.FF.FF.FF is t he Et her net br oadcast addr ess) . The r eplying device ( w hich is
eit her t he I P addr ess of t he device being sought or t he r out er t hat know s t he way) r eplaces t he
br oadcast addr ess w it h t he t ar get 's MAC addr ess, swaps t he sender and t ar get pair s, and unicast s
t he answ er dir ect ly back t o t he request ing m achine. ARP updat es t he ARP Table for fut ur e r efer ence
and t hen sends t he packet t o t he MAC addr ess t hat r eplied.
41.1.2.2 ARP Learning Mode
The Swit ch suppor t s t hr ee ARP lear ning m odes: ARP- Reply, Grat uit ous- ARP, and ARP- Request .
ARP-Reply
The Sw it ch in ARP- Reply lear ning m ode updat es t he ARP t able only w it h t he ARP r eplies t o t he ARP
r equest s sent by t he Sw it ch. This can help pr event ARP spoofing.
I n t he following exam ple, t he Swit ch does not have I P addr ess and MAC addr ess m apping
infor m at ion for host s A and B in it s ARP t able, and host A want s t o ping host B. Host A sends an
Содержание GS2210-24
Страница 18: ...18 PART I User s Guide ...
Страница 33: ...33 PART II Technical Reference ...
Страница 110: ...Chapter 9 VLAN GS2210 Series User s Guide 110 Figure 83 Advanced Application VLAN Port Based VLAN Setup All Connected ...
Страница 111: ...Chapter 9 VLAN GS2210 Series User s Guide 111 Figure 84 Advanced Application VLAN Port Based VLAN Setup Port Isolation ...
Страница 178: ...Chapter 21 Classifier GS2210 Series User s Guide 178 Figure 127 Classifier Example ...
Страница 405: ...Chapter 51 Configure Clone GS2210 Series User s Guide 405 Figure 286 Management Configure Clone ...
Страница 433: ...Appendix D Legal Information GS2210 Series User s Guide 433 Environmental Product Declaration ...