CCNA Exam Success Depends Partially On Knowing The Details Of ISDN, And There Are Plenty Of Them! To Help You Review For Your CCNA Exam, Here Are A Few ISDN Details That You Must Know On Exam Day. (They Help In The Real World, Too And There Are Still Plenty Of ISDN Networks Out There!The Cisco-proprietary Version Of HDLC Is The Default Encapsulation Type For Serial And ISDN Interfaces.R2show Interface Serial0Serial0 Is Up, Line Protocol Is Up Hardware Is HD64570 MTU 1500 Bytes, BW 1544 Kbit, DLY 20000 Usec, Rely 255255, Load 1255 Encapsulation HDLC, Loopback Not Set, Keepalive Set (10 Sec)While Theres Only One D-channel In BRI, PRI (US) And PRI (EU), The Bandwidth Of That D-channel Does Vary From BRI To PRI. Its 16 Kbps In BRI And 64 Kbps In Both PRI Versions.The Global Command Isdn Switch-type Must Be Configured Before You Can Even Begin To Have ISDN Work. Show Isdn Status Will Tell You Whether Or Not Youve Done This Correctly.R2show Isdn Status No Global ISDN Switchtype Currently Defined ISDN BRI0 Interface Dsl 0, Interface ISDN Switchtype None Layer 1 Status: DEACTIVATED Layer 2 Status: Layer 2 NOT Activated Layer 3 Status: 0 Active Layer 3 Call(s)PAP Allows Passwords To Be Different; CHAP Requires That They Be The Same.PAP Requires The Ppp Pap Sent-username Interface-level Command. CHAP Has No Equivalent Command.Define Interesting Traffic With Dialer-list And Link That List To The Interface With Dialer-group.R2conf TR2(config)dialer-list 1 Proto Ip PermitR2(config)int Bri0R2(config-if)dialer-group 1The Dialer Idle-timeout Value Is Expressed In Seconds, Not Minutes. (Even IOS Help Isnt Totally Clear On This.)R2(config)int Bri0R2(config-if)dialer-group 1R2(config-if)dialer Idle-timeout ? 1-2147483 Idle Timeout Before Disconnecting A CallR2(config-if)dialer Idle-timeout 120Dialer Map Maps A Remote IP Address To A Remote Phone Number. You Never Dial The Local Routers Phone Number.dialer Load-threshold Requires The Ppp Multilink Command To Be Configured, And The Value Of Dialer Load-threshold Is Expressed As A Ratio Of 255, NOT 100. For Example, If You Want The Second B-channel To Come Up When The First Reaches 50 Of Capacity, The Value To Express With Dialer Load-threshold Would Be 50 Of 255 Which Equals 127.R2(config)int Bri0R2(config-if)encap PppR2(config-if)ppp MultilinkR2(config-if)dialer Load-threshold ? 1-255 Load Threshold To Place Another CallSuccess On The CCNA Exam Depends On Knowing The Details. Keep Studying, Keep Practicing On Real Cisco Routers And Switches, Keep A Positive Attitude, And You're On Your Way To CCNA Exam Success!
