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Forum Replies

  1. For non-static clients’ IPs we can use local pools or dhcp:

    ! ------ R2 Client
    interface Dialer0
     ip address dhcp
    ! or
    !ip address negotiated
    ! ------ R1 Server
    ip dhcp excluded-address
    ip dhcp pool PPPoE 
    ! or
    ! ip local pool PPPoE
    interface Virtual-Template1
     peer ip address forced 
     peer default ip address dhcp-pool PPPoE
    ! or
    !peer ip address forced
    !peer default ip address pool PPPoE

    The local pools differ from the DHCP in assigning /32 to the clients.
    The OSPF RFC says

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  2. Hi,
    I think there is not enough coverage in CCNP ROUTE topics on on PPPoE vpdn and more for the exam topic. Can this be improved as per the exam guide lines

  3. Hello Hussein.

    What you are describing is a point that is often misunderstood and it is good that you bring it up. If you have an MTU of 1500 bytes on the dialler and virtual template and you are running PPPoE, then any and all packets that are 1492 bytes and smaller will be transmitted successfully and any of size larger than 1500 will be fragmented and will pass (if the DF bit is set to 0).

    The problem arises when there are packets of sizes 1493 to 1500. In this case, the virtual template and dialler will allow it through without fragmenting it but the PPPo

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  4. Hello @lagapides

    My LAB contain only two routers one is the PPPoE server and the other is PPPoE client :-


    And yes you are right based on my previous message the pings were failing at a size of 1493 bytes and this happened only when DF-bit set to 1, so this mean the fragmentation occur when the packet size is above 1492 bytes and as I know the IP MTU command tell the router at which size in bytes the IP packet should be fragment and since the IP MTU on both vi

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  5. Hi Kevin,

    I’d start with a couple of debug commands:

    • debug ppp
    • debug dialer
    • debug pppoe

    That should show something when it’s flapping. About VPDN, I just checked but I don’t think you can do this for PPPoE on the client. Here’s what I have on IOS 15:

    Client(config)#vpdn enable 
    Client(config)#vpdn-group MY_GROUP
    Client(config-vpdn-req-out)#protocol ?
      l2tp  Use L2TP

    I looked around to see if there is anything for IOS 12.4 but I don’t think so. On the ASA, it seems to be possible:


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