[cisco-nas] Problems with multilink PPP/ISDN

[Mark Johnson]

At 11:47 AM 1/9/2004 +0100, Regnar Bang Lyngsø wrote:
>Hi,
>
>I am experiencing problems that I can't understand.
>
>I have a Cisco 3600 with an ISDN PRI and I can't get ISDN-2 Multilink PPP
>(128K) to work and I really don't know why.
>
>Everything works fine with a single 64K ISDN channel. Also, multilink PPP
>with one ISDN channel and an analog modem connection works fine.
>
>Clients are various Windows Workstations with Lasat and Zyxel ISDN modems.
>
>Radius server is MS IAS with the following parameters set:
>Framed-Protocol: PPP
>Service-type: Framed
>Filter-Id: depending on profile
>
>The following is debug output (I would like to know what the "Ignoring bad
>ACK!" message means):

Each PPP Control Protocol packet has an ID associated with it, along with
the different options being requested; the response (ACK) to this packet
must have the same ID and the options can't be reordered or modified in
any way.  If this is not the case, we will print out this message.

It typically indicates some sort of delay or processing error on the
part of the PPP peer.

>00:13:14: %LINK-3-UPDOWN: Interface Serial3/0:0, changed state to up
>00:13:15: %LINK-3-UPDOWN: Interface Serial3/0:1, changed state to up
>00:13:15: %ISDN-6-CONNECT: Interface Serial3/0:0 is now connected to 443
>00:13:17: Se3/0:0 LCP: Ignoring bad ACK!

<debug ppp neg> would indicate what's happening here, but I suspect
the clients are having issues.

>00:13:19: Se3/0:0 EVT: Packet suspended unexpectedly
>00:13:21: %ISDN-6-CONNECT: Interface Serial3/0:1 is now connected to 443
>00:13:22: Se3/0:0 LCP: Ignoring bad ACK!
>00:13:25: %ISDN-6-DISCONNECT: Interface Serial3/0:1  disconnected from 443
>, call lasted 10 seconds
>00:13:25: %LINK-3-UPDOWN: Interface Serial3/0:1, changed state to down
>00:13:25: %ISDN-6-DISCONNECT: Interface Serial3/0:0  disconnected from 443
>071f1c, call lasted 10 seconds
>00:13:25: %LINK-3-UPDOWN: Interface Serial3/0:0, changed state to down

>interface Serial3/0:15
>  no ip address
>  encapsulation ppp
>  ip mroute-cache
>  dialer rotary-group 1
>  dialer-group 1
>  autodetect encapsulation ppp v120
>  isdn switch-type primary-net5
>  isdn incoming-voice modem
>  peer default ip address dhcp
>  no cdp enable
>  ppp authentication ms-chap-v2 chap pap ms-chap
>  ppp multilink
>!
>interface Virtual-Template1
>  ip unnumbered Loopback0
>  peer default ip address dhcp
>  ppp authentication ms-chap-v2 chap pap ms-chap
>  ppp multilink
>!
>interface Dialer1
>  ip unnumbered Loopback0
>  encapsulation ppp
>  dialer in-band
>  dialer idle-timeout 3600
>  dialer-group 1
>  peer default ip address dhcp
>  no cdp enable
>  ppp authentication ms-chap-v2 chap pap ms-chap
>  ppp multilink

Again, <debug ppp neg> would confirm what's going on with negotiations,
but I suspect you'll have to take a closer look at the ISDN modems.

mark