Information Technology Reference
In-Depth Information
Table17-11 PPP LCP Negotiation Details (continued)
Time Stamp
Description
10:57:17.047
to
10:57:17.191
PPP authentication is completed successfully. After LCP negotiates,
authentication starts. Authentication must take place before any
network protocols, such as IP, are delivered.
Both sides authenticate with the method negotiated during LCP.
Montecito is authenticating the client using CHAP.
10:57:20.551
The state is open for IP Control Protocol (IPCP). A route is
negotiated and installed for the IPCP peer, which is assigned IP
address 1.1.1.1.
Link Control Protocol
Two types of problems are typically encountered during LCP negotiation. The first occurs when one peer
makes configuration requests that the other peer cannot or will not acknowledge. Although this is a
frequent occurrence, it can be a problem if the requester insists on the parameter. A typical example is
when negotiating AUTHTYPE. For instance, many access servers are configured to accept only CHAP
for authentication. If the caller is configured to do only PAP authentication, CONFREQs and
CONFNAKs will be exchanged until one peer drops the connection.
BR0:1 LCP: I CONFREQ [ACKrcvd] id 66 len 14
BR0:1 LCP: AuthProto PAP (0x0304C023)
BR0:1 LCP: MagicNumber 0xBC6B9F91 (0x0506BC6B9F91)
BR0:1 LCP: O CONFNAK [ACKrcvd] id 66 len 9
BR0:1 LCP: AuthProto CHAP (0x0305C22305)
BR0:1 LCP: I CONFREQ [ACKrcvd] id 67 len 14
BR0:1 LCP: AuthProto PAP (0x0304C023)
BR0:1 LCP: MagicNumber 0xBC6B9F91 (0x0506BC6B9F91)
BR0:1 LCP: O CONFNAK [ACKrcvd] id 67 len 9
BR0:1 LCP: AuthProto CHAP (0x0305C22305)
BR0:1 LCP: I CONFREQ [ACKrcvd] id 68 len 14
BR0:1 LCP: AuthProto PAP (0x0304C023)
BR0:1 LCP: MagicNumber 0xBC6B9F91 (0x0506BC6B9F91)
BR0:1 LCP: O CONFNAK [ACKrcvd] id 68 len 9
BR0:1 LCP: AuthProto CHAP (0x0305C22305)
. . . and so on.
The second type of problem seen in LCP is when
only
outbound CONFREQs are seen on one or both
peers, as in the example that follows. This is usually the result of what is referred to as a
speed mismatch
at the lower layer. This condition can occur in either async or ISDN DDR.
