Specifications

AP Overview
9-8 Configuring Access Points
TheprocessskipstoStep 6onpage 9‐8.
•IfnoRoamAboutSwitchesreply,theAPrepeatedlyresendstheFindRASbroadcast.If
stillnoRoamAboutSwitchesreply,theprocesscontinueswithStep 3onpage 9‐8.
3. IftheAPisunabletolocateaRoamAboutSwitchonthesubnetitisconnectedto,
andis
unabletofindaRoamAboutSwitchbasedoninformationintheDHCPoption43field,theAP
sendsDNSrequestsforwlan‐switch,wheretheDNSsuffixformynetwork.comislearned
throughDHCP.
4. TheDNSserverreplieswiththesystemIPaddressofaRoamAboutSwitch.Ifwlan
‐switchis
definedinDNS,theAPsendsaunicastFindRASmessagetotheRoamAboutSwitchwhose
IPaddressisreturnedforwlan‐switch.
5. TheAPsendsFindRASrequeststotheRoamAboutSwitchIPaddressesgivenbytheDNS
reply.IfaRoamA bou tSwitchreceivestheFindRAS
Request,theprocesscontinueswith
Step 6onpage 9‐8.
However,ifnoRoamAboutSwitchswitchesreply,theAPrepeatedlyretriesthismethod:
•IfstillnoRoamAboutSwitchesreply,theAPbeginstheprocessagain,startingwiththe
procedureunder“HowanAPContactsaRoamAboutSwitch(DHCP‐Obtained
Address)”onpage 9‐
7,ontheotherAPport.
•IftheotherAPportdoesnothavealinkortheAPhasonlyoneport,theAPinstead
restarts,andbeginstheprocessagainonthesameAPport.
6. TheRoamAboutSwitchthatreceivestheFindRASrequestdeterminesthebestRoamAbout
SwitchfortheAPtouse,basedonthebiassettingsfor theAPoneachswitch.Ifmorethanone 
switchhashighbiasfortheAPorallswitcheshavethesamebias,theRoamAboutSwitch
suggeststheswi tch thathasthehighestcapacitytoaddnewactiveAP
connections.
7. TheRoamAboutSwitchsendsaunicastFindRASReplymessagetotheAPcontainingthe
systemIPaddressofthebestRoamAboutSwitchtouse.
8. TheAPsendsaunicastmessagetothesuggestedRoamAboutSwitch,torequestan
operationalimage.IftheAPdoesnotreceiveareplyafter
10seconds,theAPrebootsand
startsthebootprocessover.
IfanAPdoesnotreceiveareplytoaDNSrequestorarequestforanoperationalimageafter
oneminute,theAPstartsthebootprocessoverwithanewDHCPDiscovermessage,thistime
fromAPport
2.
How a Distributed AP Contacts an RBT Switch (Statically Configured Address)
WhenconfiguringadistributedAPwithstaticIPinformation,youcanspecifythefollowing
information:
A. IPaddress,subnetmask,defaultrouter,andwhethertheconfiguredstaticIPaddress
informationisenabledfortheAP.
B. TheIPaddressofasuitableRoamAboutSwitchfortheAPtouseasabootdevice.
C. The
fullyqualifieddomainnameofanRoa m AboutSwitchtouseasabootdevice,andthe
IPaddressofaDNSserverusedtoresolvetheRoamAboutSwitch’s name.
Note: You must configure a DNS address record on your DNS server for the
RoamAbout Switch IP address. Otherwise, the DNS server cannot provide the
RoamAbout Switch’s address to the AP.