CHAP Authentication Process Call

1
CHAP Authentication Process - Call
User dials in
Branch
Central
2
CHAP Authentication Process - Challenge
User dials in
01 id random Central
Branch
Central
01 CHAP Challenge packet identifier id
sequential number identifying challenge random
random number Central authentication name of
challenger
3
CHAP Authentication Process - Response
User dials in
01 id random Central
Branch
Central
User pass Central pass
MD5
4
CHAP Authentication Process Response cont.
User dials in
01 id random Central
Branch
Central
User pass Central pass
02 id hash Branch
02 CHAP Response packet identifier id
sequential number identifying challenge hash
hash value from MD5 Branch authentication name
of caller
MD5
5
CHAP Authentication Process Verification
User dials in
01 id random Central
Branch
Central
User pass Central pass
User pass Branch pass
02 id hash Branch
MD5
6
CHAP Authentication Process Result
User dials in
01 id random Central
Branch
Central
User pass Central pass
User pass Branch pass
02 id hash Branch
03 id Welcome
OR
04 id Failure
7
Configuring CHAP
BranchOffice
CentralOffice
ISDN
Router(config) hostname CentralOffice CentralOffi
ce(config) enable secret class CentralOffice(conf
ig) username BranchOffice password
class CentralOffice(config) int
bri0/0 CentralOffice(config-if) ip address
10.10.10.1 255.255.255.0 CentralOffice(config-if)
encapsulation ppp CentralOffice(config-if) ppp
authentication chap
CentralOffice(config-if) username left password
cisco
8
Configuring CHAP cont.
BranchOffice
CentralOffice
ISDN
Router(config) hostname BranchOffice BranchOffice
(config) enable secret class BranchOffice(config)
dialer-list 1 protocol ip permit BranchOffice(co
nfig) int bri0/0 BranchOffice(config-if) ip
address 10.10.10.2 255.255.255.0 BranchOffice(conf
ig-if) encapsulation ppp BranchOffice(config-if)
ppp authentication chap BranchOffice(config-if)
dialer-group 1 BranchOffice(config-if) dialer
string 5551212 BranchOffice(config-if)
dialer-map ip 10.10.10.1 name CentralOffice
555-2121
Router(config-if) ppp chap hostname
left Router(config-if) ppp chap password cisco