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Does LCP negotiate IPCP during the establishment of a PPP

dignitydignity Member Posts: 10 ■□□□□□□□□□
in CCNA & CCENT
or NCP does this .. which one negotiate ICP
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    tunerXtunerX Member Posts: 447 ■■■□□□□□□□
    You are kind of misusing terms.

    NCP (Network Control Protocol) is a generic term. It is just an acronym that represents all of the Layer 3 control protocols (IPXCP, IPCP, IPv6CP, ...etc).

    You are correct in both respects.

    LCP is in control of layer 2. Once LCP Is completely up and running the specific NCP is started based on the interface configuration, either IPCP, IPv6CP, ... etc.

    Layer 1 - physical interface clock and control (ISDN, Analog, RS449, RS232, ...etc)

    Layer 2 - LCP (Layer 2 options and authentication)

    Layer 3 - NCP (IPCP, IPXCP, IPv6CP, ...etc)
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    dignitydignity Member Posts: 10 ■□□□□□□□□□
    what if they ask this question in exam ..shall be sure lcp negotiates ; authentication, multilink , callback not IPCP since its layer 3..
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    tunerXtunerX Member Posts: 447 ■■■□□□□□□□
    LCP does everything that is related to layer 2. PPP moves the process from layer 2 to layer 3, after LCP is completed. If you look at the following debug message you will see that PPP does LCP then IPCP. In the debug you see "LCP: State is Open". That is it, LCP is done with its part in PPP. PPP then goes on to say that "PPP: Phase is UP"; this means that PPP is now moving from LCP (layer 2). PPP looks at the configuration of your interface, it sees that the configuration is configured with IP so it will now start the IPCP process. It is pretty tricky, you can say that IPCP is layer 2 but it is not, it is a transition between layer 2 to layer 3. Once IPCP is completed, you can now send IP traffic across the link. For the test I would say that IPCP is layer 2, but in reality I would say that IPCP is the first stage of layer 3.

    Router# debug ppp negotiation
    *Mar 2 02:25:27.693: %LINK-3-UPDOWN: Interface Serial0/0, changed state to up
    *Mar 2 02:25:27.693: Se0/0 PPP: Treating connection as a dedicated line
    *Mar 2 02:25:27.693: Se0/0 PPP: Phase is ESTABLISHING, Active Open
    *Mar 2 02:25:27.693: Se0/0 LCP: O CONFREQ [Closed] id 11 len 10
    *Mar 2 02:25:27.693: Se0/0 LCP: MagicNumber 0x35C4DB07 (0x050635C4DB07)
    *Mar 2 02:25:27.729: Se0/0 LCP: I CONFREQ [REQsent] id 14 len 29
    *Mar 2 02:25:27.729: Se0/0 LCP: MagicNumber 0xBFAE7481 (0x0506BFAE7481)
    *Mar 2 02:25:27.729: Se0/0 LCP: MRRU 1524 (0x110405F4)
    *Mar 2 02:25:27.729: Se0/0 LCP: EndpointDisc 1 Local (0x130F01696F7377616ED3 23630 3063)
    *Mar 2 02:25:27.729: Se0/0 LCP: O CONFREJ [REQsent] id 14 len 23
    *Mar 2 02:25:27.729: Se0/0 LCP: MRRU 1524 (0x110405F4)
    *Mar 2 02:25:27.733: Se0/0 LCP: EndpointDisc 1 Local (0x130F01696F7377616ED3 23630 3063)
    *Mar 2 02:25:27.733: Se0/0 LCP: O CONFACK [REQsent] id 15 len 10
    *Mar 2 02:25:27.733: Se0/0 LCP: MagicNumber 0xBFAE7481 (0x0506BFAE7481)
    *Mar 2 02:25:27.733: Se0/0 LCP: State is Open
    *Mar 2 02:25:27.733: Se0/0 PPP: Phase is UP
    *Mar 2 02:25:27.737: Se0/0 IPCP: O CONFREQ [Closed] id 10 len 16
    *Mar 2 02:25:27.737: Se0/0 IPCP: CompressType VJ 15 slots (0x0206002D0F00)
    *Mar 2 02:25:27.737: Se0/0 IPCP: Address 10.1.30.200 (0x03060A011ECicon_cool.gif
    *Mar 2 02:25:27.745: Se0/0 LCP: I CONFACK [Open] id 11 len 10
    *Mar 2 02:25:27.745: Se0/0 LCP: MagicNumber 0x35C4DB07 (0x050635C4DB07)
    *Mar 2 02:25:27.777: Se0/0 LCP: I CONFREQ [Open] id 15 len 10
    *Mar 2 02:25:27.781: Se0/0 LCP: MagicNumber 0xBFAE7481 (0x0506BFAE7481)
    *Mar 2 02:25:27.781: Se0/0 LCP: Dropping packet, state is Open
    *Mar 2 02:25:27.813: Se0/0 IPCP: I CONFREQ [REQsent] id 105 len 28
    *Mar 2 02:25:27.813: Se0/0 IPCP: CompressType VJ 15 slots (0x0206002D0F00)
    *Mar 2 02:25:27.813: Se0/0 IPCP: Address 0.0.0.0 (0x030600000000)
    *Mar 2 02:25:27.813: Se0/0 IPCP: PrimaryDNS 0.0.0.0 (0x810600000000)
    *Mar 2 02:25:27.813: Se0/0 IPCP: SecondaryDNS 0.0.0.0 (0x830600000000)
    *Mar 2 02:25:27.813: Se0/0 IPCP: Pool returned 10.1.30.109
    *Mar 2 02:25:27.817: Se0/0 IPCP: O CONFREJ [REQsent] id 105 len 16
    *Mar 2 02:25:27.817: Se0/0 IPCP: PrimaryDNS 0.0.0.0 (0x810600000000)
    *Mar 2 02:25:27.817: Se0/0 IPCP: SecondaryDNS 0.0.0.0 (0x830600000000)
    *Mar 2 02:25:27.817: Se0/0 IPCP: O CONFNAK [REQsent] id 106 len 10
    *Mar 2 02:25:27.817: Se0/0 IPCP: Address 10.1.30.109 (0x03060A011E6D)
    *Mar 2 02:25:27.817: Se0/0 IPCP: O CONFACK [REQsent] id 107 len 16
    *Mar 2 02:25:27.817: Se0/0 IPCP: CompressType VJ 15 slots (0x0206002D0F00)
    *Mar 2 02:25:27.821: Se0/0 IPCP: Address 10.1.30.109 (0x03060A011E6D)
    *Mar 2 02:25:27.833: Se0/0 IPCP: I CONFACK [ACKsent] id 10 len 16
    *Mar 2 02:25:27.833: Se0/0 IPCP: CompressType VJ 15 slots (0x0206002D0F00)
    *Mar 2 02:25:27.833: Se0/0 IPCP: Address 10.1.30.200 (0x03060A011ECicon_cool.gif
    *Mar 2 02:25:27.833: Se0/0 IPCP: State is Open
    *Mar 2 02:25:27.837: Se0/0 IPCP: Install route to 10.1.30.109
    *Mar 2 02:25:27.837: Se0/0 IPCP: Add link info for cef entry 10.1.30.109
    *Mar 2 02:25:27.861: Se0/0 IPCP: I CONFREQ [Open] id 106 len 16
    *Mar 2 02:25:27.865: Se0/0 IPCP: CompressType VJ 15 slots (0x0206002D0F00)
    *Mar 2 02:25:27.865: Se0/0 IPCP: Address 0.0.0.0 (0x030600000000)
    *Mar 2 02:25:27.865: Se0/0 IPCP: Dropping packet, state is Open
    *Mar 2 02:25:27.881: Se0/0 IPCP: I CONFREQ [Open] id 107 len 16
    *Mar 2 02:25:27.885: Se0/0 IPCP: CompressType VJ 15 slots (0x0206002D0F00)
    *Mar 2 02:25:27.885: Se0/0 IPCP: Address 10.1.30.109 (0x03060A011E6D)
    *Mar 2 02:25:27.885: Se0/0 IPCP: Dropping packet, state is Open
    *Mar 2 02:25:28.733: %LINEPROTO-5-UPDOWN: Line protocol on Interface Serial0/, changed state to up
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    pad10029pad10029 Member Posts: 27 ■□□□□□□□□□
    thanks for bringing this up dignity....

    thanks tunerX, you'll have use all passing the ccna yet :D
    keep it coming....
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