PPPoE configuration

Discussion in 'Cisco' started by Frank Winkler, Mar 12, 2008.

  1. Hi there !

    I have some trouble configuring a DSL connection. The relevant part of the
    config looks like


    vpdn enable
    vpdn-group pppoe
    protocol pppoe
    interface FastEthernet0/1
    description WAN - to DSL modem
    no ip address
    ip nat outside
    no ip virtual-reassembly
    duplex auto
    speed auto
    pppoe enable group global
    pppoe-client dial-pool-number 1
    no cdp enable
    interface Dialer1
    description DSL
    ip address negotiated
    ip mtu 1492
    ip nat outside
    ip virtual-reassembly
    encapsulation ppp
    no ip route-cache
    no ip mroute-cache
    dialer pool 1
    dialer-group 1
    no cdp enable
    ppp pap sent-username XXX password 7 XXX
    ppp ipcp dns request
    ip route Dialer1 permanent
    ip nat inside source list 100 interface Dialer1 overload
    access-list 100 permit ip any any
    dialer-list 1 protocol ip permit


    The connection seems to fail at a very early stage as I get "padi timer
    expired". Any hints what's wrong? A very similar configuration worked on a
    different router model and with a different DSL provider some years ago.
    And a Netgear consumer router can establish a PPPoE session so the line
    looks ok.


    Frank Winkler, Mar 12, 2008
    1. Advertisements

  2. Frank Winkler

    Bod43 Guest

    That all looks good campared with one I used
    a while back.

    debug ppp neg
    debug ppp auth

    One thing might be that they are using chap and not pap.

    If you havent done it before you will have to
    get debug working.

    logg buffered debug datetime ms
    logg buffered 50000

    debug this and that
    clear int di 1
    sh logg

    Should do it.
    Bod43, Mar 12, 2008
    1. Advertisements

  3. If this was the case, wou;ldn't I then run into an auth issue instead? IMO
    we don't get this far at the moment. And are you sure that DSL providers
    are using CHAP for consumer access? Well ... the Netgear seems to know both
    but how does it know which one to use as it's not configurable?

    I'll try some more debugging.


    Frank Winkler, Mar 12, 2008
  4. Frank Winkler


    Dec 16, 2007
    Likes Received:
    I have seen this before odds are the Netgear is going to auto negotiate the authentication type while the firewall is hard coded to only set it up with pap. Take this odd and add the line below and see if it takes the authentication of connection out of the troubleshooting.

    no ppp pap sent-username XXX password 7 XXX

    ppp chap sent-username XXX password 7 XXX

    Greeley, Mar 12, 2008
  5. Frank Winkler

    Darren Green Guest


    I have little experience with pppoe but a quck search of the Cisco WWW
    site provided this URL:



    'In this example, the Cisco DSL router continuously sends PPPoE Active
    Discovery Initiation (PADI) frames to the ISP with no response. The
    PADI frame is the first in a series of PPPoE call-setup frames. If
    your ISP does not respond with a PPPoE Active Discovery Offer (PADO),
    PPPoE negotiation does not succeed. The only solution for this problem
    is to contact your ISP'



    Darren Green, Mar 12, 2008
  6. Frank Winkler

    Merv Guest

    PPPoE is executed in two stages. The first stage is PPPoE session
    and the second stage is the PPP negotiation. PPPoE session must be
    prior to the negotiation of standard PPP parameters ( this is when
    authentication will occur).

    It sounds as if the PPPOE discovery stage is not completing

    PPPOE discovery stage consists of the following exchanges:

    .. router sends a PPPoE Active Discovery Initiation (PADI) packet to
    ISP access device

    .. ISP access device send a PPPoE Active Discovery Offer (PADO) packet
    to router

    .. router sends a The PPPoE Active Discovery Request (PADR) packet to
    ISp access device

    .. ISP access device send a PPPoE Active Discovery Session-confirmation
    (PADS) packet to router

    Use the show vpdn command to determine the state of the PPPOE session
    Merv, Mar 12, 2008
  7. I also found that.
    That would have been an option unless ...

    ACK - but why and how does a dumb Netgear do it at exactly the same line?


    Frank Winkler, Mar 13, 2008
  8. Frank Winkler

    Merv Guest

    not sure if it matter but every PPOE config I have see just has

    pppoe enable

    you have

    pppoe enable group global
    Merv, Mar 13, 2008
  9. Frank Winkler

    Merv Guest

    what model of Netgear router ?

    what are all of the parameters that you set for PPPOE on the the
    Netgear ?

    do you specify a service-name on the Netgear ?
    Merv, Mar 13, 2008
  10. That's a good old FM114P
    Just user name and PW


    Frank Winkler, Mar 13, 2008
  11. Frank Winkler

    Merv Guest

    Did you have to register the MAC address of your Netgear with your
    Merv, Mar 13, 2008
  12. Nope.
    Frank Winkler, Mar 13, 2008
  13. Frank Winkler

    Merv Guest

    1. disconnect cable from router that goes to DSL modem

    2 clear interface counters

    3. reconnect cable

    4. post the output of show interface fa 0/1 after you see PADI timer
    expired message
    Merv, Mar 13, 2008
  14. Thanks, I'll do that ASAP but it'll take some time as this installation is
    on a different site and I'll have to talk to my friend there.


    Frank Winkler, Mar 13, 2008
  15. Frank Winkler

    Merv Guest


    Also add in a post of show version
    Merv, Mar 13, 2008
  16. It's a 1841 mit 12.4.18 advip - is that what you want? ;)


    Frank Winkler, Mar 13, 2008
  17. Frank Winkler

    Merv Guest

    make sure the fast ethernet interface is in up and up state

    I did a test in my lab and found that debug pppoe packet still spits
    out padi packet even thou the configured ethernet interface is down

    HUB#debug pppoe packet
    PPPoE control packets debugging is on
    000093: *Mar 1 01:01:27.697: pppoe_send_padi:
    FF FF FF FF FF FF 00 B0 64 4C E5 40 88 63 11 09
    00 00 00 0C 01 01 00 00 01 03 00 04 82 7C 13 20 ...
    HUB#sh int e 0/0
    Ethernet0/0 is up, line protocol is down
    Hardware is AmdP2, address is 00b0.644c.e540 (bia 00b0.644c.e540)
    Description: +++ LAN
    MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,
    reliability 227/255, txload 1/255, rxload 1/255
    Encapsulation ARPA, loopback not set
    Keepalive set (10 sec)
    ARP type: ARPA, ARP Timeout 04:00:00
    Last input 00:01:57, output 00:00:05, output hang never
    Last clearing of "show interface" counters 00:51:05
    Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops:
    Queueing strategy: fifo
    Output queue: 0/40 (size/max)
    5 minute input rate 0 bits/sec, 0 packets/sec
    5 minute output rate 0 bits/sec, 0 packets/sec
    7 packets input, 1288 bytes, 0 no buffer
    Received 7 broadcasts, 0 runts, 0 giants, 0 throttles
    0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
    0 input packets with dribble condition detected
    402 packets output, 24120 bytes, 0 underruns
    13 output errors, 0 collisions, 0 interface resets
    0 babbles, 0 late collision, 0 deferred
    14 lost carrier, 0 no carrier
    000094: *Mar 1 01:01:59.801: pppoe_send_padi:
    FF FF FF FF FF FF 00 B0 64 4C E5 40 88 63 11 09
    00 00 00 0C 01 01 00 00 01 03 00 04 82 7C 13 20 ...
    Merv, Mar 13, 2008
  18. Ah, you basically wanted to know if the interface is up? Yes, it is. Even
    if I have some PPPoE trouble, I'm not a greenhorn ;) ...

    I hope to get the debugging results this evening but if it's just the
    interface state, I can tell you it's ok.


    Frank Winkler, Mar 14, 2008
  19. Frank Winkler

    Merv Guest

    That was the purpose of the question and the output; but please do
    post the requested show interface output along with debug ppoe packet

    Is the cable between the DSL modem and teh Cisco router a straight-
    thru or a crossover cable ?

    Is the same cable used to connect DSL modem to the the Netgear
    router ?

    What is the make and model of the DSL modem ?

    Who is the ISP?

    Can you connect a Windows PC and enable PPPOE client and get access ?

    If so use WireShark t(www.wireshark.org) to capture the PPPOE packets
    sent and received

    Basically all the PPPOE PADI packet contains is the MAC address of the
    PPPOE client and it is sent with a broadcast destination MAC address.
    Merv, Mar 14, 2008
  20. I'll do so.
    I'm not 100% sure but I suppose it's straight-thru.
    It's Sphairon Turbolink AR871C1-B - he got that one for ADSL2+ as a
    replacement for an Alcatel on the ADSL2 line.
    It's local German provider, called m-net.
    No, we don't have Billy-OS but a Mac doing the PPPoE stuff does also get
    access ...
    .... so it doesn't seem to be a MAC address issue.


    Frank Winkler, Mar 14, 2008
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.