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Solving PPP Problems        4


Use Table 4-1 to identify and diagnose some common Point-to-Point Protocol (PPP) problems.

  Table 4-1 Common PPP Problems

Problem

Possible Cause

Possible Solution

A connection fails while the PortMaster is negotiating PPP.

Authentication failure and/or protocol negotiation failure.

See "Debugging and Interpreting PPP Negotiation" on page 4-2.

Multichassis PPP is not functioning.

All the chassis used in Multichassis PPP are not on the same Ethernet segment.

See "Diagnosing Multichassis PPP Problems" on page 4-5.

When using Multichassis PPP, calls do not roll over to the next chassis.

Misconfigured endpoint discriminator.

 See "Endpoint Discriminator Misconfiguration" on page 4-6.

A user cannot dial in to a PortMaster that is using Multichassis PPP.

A suspended session for a particular user.

 See "Dial-In Problems with Multichassis PPP" on page 4-7

When using Multilink PPP or Multichassis PPP, calls do not roll over to the next chassis.

Incorrect configuration at the telephone company.

 See "Diagnosing a Hunt Group Rollover Problem" on page 4-8.

Compression is not working correctly.

Compression history slots are not being released.

 See "Troubleshooting Compression" on page 4-10.

Debugging and Interpreting PPP Negotiation You can debug and interpret the PPP negotiation process using the commands and information in this section.

  1. To debug PPP negotiations, enter the following commands on the PortMaster:

    Command> set console
    Command> set debug 0x51

The set debug 0x51 command allows observation of PPP negotiation, such as the following example:
Sending LCP_CONFIGURE_REQUEST to port S1 of 24 bytes containing:

01 01 00 18 02 06 00 00 00 00 05 06 d4 55 9b ea 07 02 08 02 03 04 c0 23

Received LCP_CONFIGURE_ACK on port S1 of 20 bytes containing:

02 01 00 18 02 06 00 00 00 00 05 06 d4 55 9b ea 07 02 08 02 03 04 c0 23

Received LCP_CONFIGURE_REQUEST on port S1 of 16 bytes containing:

01 03 00 14 02 06 00 00 00 00 05 06 2b 3a eb 57 07 02 08 02

Sending LCP_CONFIGURE_ACK to port S1 of 20 bytes containing:

02 03 00 14 02 06 00 00 00 00 05 06 2b 3a eb 57 07 02 08 02

S1: LCP Open

Received PAP_AUTH_REQ on port S1 of 24 bytes containing:

01 01 01 11 01 6b 71 73 6a 71 6f 72 2a 68 76 09 36 31 35 37 32 34 36 39

Sending PAP_AUTH_ACK to port S1 of 20 bytes containing:

02 01 00 14 0f 4c 6f 67 69 6e 20 53 75 63 63 65 65 64 65 64

Sending IPCP_CONFIGURE_REQUEST to port S1 of 16 bytes containing:

01 01 00 10 02 06 00 2d 0f 00 03 06 c0 a8 05 19

Received IPCP_CONFIGURE_REQUEST on port S1 of 12 bytes containing:

01 01 00 10 02 06 00 2d 0f 00 03 06 c0 a8 0a 20

Sending IPCP_CONFIGURE_ACK to port S1 of 16 bytes containing:

02 01 00 10 02 06 00 2d 0f 00 03 06 c0 a8 0a 20

Received IPCP_CONFIGURE_ACK on port S1 of 12 bytes containing:

02 01 00 10 02 06 00 2d 0f 00 03 06 c0 a8 05 19

S1: IPCP Open

LCP IPCP Open

Connection Succeeded

 

Caution ¯ User IDs and passwords are transmitted at the "Received PAP_AUTH_REQ" message in PPP negotiation. Anyone can use the PPP Decoder Ring to translate user IDs and passwords. Therefore, you must protect PPP debug output as you would actual passwords.

  1. Enter 0x51 debug output into the Livingston PPP Decoder Ring (dring) located at http://www.livingston.com/Tech/Support/debug-tools.shtml.
The output in the previous example is decoded as follows:
Dring: Decoder Ring for Livingston Product PPP traces
-----------------------------------------------------

Sending LCP_CONFIGURE_REQUEST to port S1 of 24 bytes containing:

01 01 00 18 02 06 00 00 00 00 05 06 D4 55 9B EA 07 02 08
02 03 04 C0 23

Packet Info: Code: 01, ID: 01, 24 bytes.
Async-Control-Character-Map [0x02], length: (6 bytes), [0x00000000]
Magic-Number [0x05], length: (6 bytes), [0xD4559BEA]
Protocol-Field-Compression [0x07], length: (2 bytes)
Address-and-Control-Field-Compression [0x08], length: (2 bytes)
Authentication-Protocol [0x03], length: (4 bytes), Password Authentication Protocol [0xC023]

Received LCP_CONFIGURE_ACK on port S1 of 20 bytes containing:
02 01 00 18 02 06 00 00 00 00 05 06 D4 55 9B EA 07 02 08
02 03 04 C0 23

Packet Info: Code: 02, ID: 01, 24 bytes.
Async-Control-Character-Map [0x02], length: (6 bytes), [0x00000000]
Magic-Number [0x05], length: (6 bytes), [0xD4559BEA]
Protocol-Field-Compression [0x07], length: (2 bytes)
Address-and-Control-Field-Compression [0x08], length: (2 bytes)
Authentication-Protocol [0x03], length: (4 bytes), Password Authentication Protocol [0xC023]

Received LCP_CONFIGURE_REQUEST on port S1 of 16 bytes containing:
01 03 00 14 02 06 00 00 00 00 05 06 2B 3A EB 57 07 02 08 02

Packet Info: Code: 01, ID: 03, 20 bytes.
Async-Control-Character-Map [0x02], length: (6 bytes), [0x00000000]
Magic-Number [0x05], length: (6 bytes), [0x2B3AEB57]
Protocol-Field-Compression [0x07], length: (2 bytes)
Address-and-Control-Field-Compression [0x08], length: (2 bytes)

Sending LCP_CONFIGURE_ACK to port S1 of 20 bytes containing:
02 03 00 14 02 06 00 00 00 00 05 06 2B 3A EB 57 07 02 08 02

Packet Info: Code: 02, ID: 03, 20 bytes.
Async-Control-Character-Map [0x02], length: (6 bytes), [0x00000000]
Magic-Number [0x05], length: (6 bytes), [0x2B3AEB57]
Protocol-Field-Compression [0x07], length: (2 bytes)
Address-and-Control-Field-Compression [0x08], length: (2 bytes)
**** S1: LCP Open

Received PAP_AUTH_REQ on port S1 of 24 bytes containing:
01 01 00 18 0A 6A 73 74 6F 72 6D 73 2D 67 77 08 31 32 33 34 35 36 37 38

Packet Info: Code: 01, ID: 01, 24 bytes.
Login ID: bart (10 bytes), [0x6A73746F726D732D6777]
Password: 12345678 (8 bytes), [0x3132333435363738]

Sending PAP_AUTH_ACK to port S1 of 20 bytes containing:
02 01 00 14 0F 4C 6F 67 69 6E 20 53 75 63 63 65 65 64 65 64

Packet Info: Code: 02, ID: 01, 20 bytes.
Message: Login Succeeded (15 bytes),
[0x4C6F67696E20537563636565646564]

Sending IPCP_CONFIGURE_REQUEST to port S1 of 16 bytes containing:
01 01 00 10 02 06 00 2D 0F 00 03 06 C0 A8 05 19

Packet Info: Code: 01, ID: 01, 16 bytes.
IP-Compression-Protocol [0x02], length: (6 bytes), Van Jacobson Compressed TCP/IP [0x002D0F00]
IP-Address [0x03], length: (6 bytes), [192.168.5.25]

Received IPCP_CONFIGURE_REQUEST on port S1 of 12 bytes containing:
01 01 00 10 02 06 00 2D 0F 00 03 06 C0 A8 0A 20

Packet Info: Code: 01, ID: 01, 16 bytes.
IP-Compression-Protocol [0x02], length: (6 bytes), Van Jacobson Compressed TCP/IP [0x002D0F00]
IP-Address [0x03], length: (6 bytes), [192.168.10.32]

Sending IPCP_CONFIGURE_ACK to port S1 of 16 bytes containing:
02 01 00 10 02 06 00 2D 0F 00 03 06 C0 A8 0A 20

Packet Info: Code: 02, ID: 01, 16 bytes.
IP-Compression-Protocol [0x02], length: (6 bytes), Van Jacobson Compressed TCP/IP [0x002D0F00]
IP-Address [0x03], length: (6 bytes), [192.168.10.32]

Received IPCP_CONFIGURE_ACK on port S1 of 12 bytes containing:
02 01 00 10 02 06 00 2D 0F 00 03 06 C0 A8 05 19

Packet Info: Code: 02, ID: 01, 16 bytes.
IP-Compression-Protocol [0x02], length: (6 bytes), Van Jacobson Compressed TCP/IP [0x002D0F00]
IP-Address [0x03], length: (6 bytes), [192.168.5.25]

**** S1: IPCP Open

**** LCP IPCP Open

Connection Succeeded

  1. Turn off debugging:

    Command> set debug off

    For information about PPP frame formats, see Appendix B, "PPP Packet Formats."

Diagnosing Multichassis PPP Problems

All PortMaster 3 chassis used for Multichassis PPP must be connected to the same Ethernet segment. Two chassis can have a switch separating them on the segment if necessary, but not a router. If Multichassis PPP is not working, verify that all the chassis in the Multichassis PPP domain are connected to the same Ethernet segment, and that no routers are connected between chassis.

Multichassis PPP problems can be diagnosed with the following show commands:

Endpoint Discriminator Misconfiguration

If connections to a Multichassis PPP domain are not rolling over from one PortMaster to another, a PortMaster might have a misconfigured endpoint discriminator. All chassis in a single Multichassis PPP domain must have the same endpoint discriminator.

To check the endpoint discriminator on each PortMaster in a Multichassis PPP domain, use the show global command:

Command> show global

 

System Name:

pm3

Default Host:

0.0.0.0

Alternate Hosts:

 

IP Gateway:

174.154.96.2

Gateway Metric:

1

Default Routing:

Quiet (Off)

OSPF Priority:

0

OSPF Router ID:

174.154.96.68 (default)

Name Service:

DNS

Name Server:

174.154.1.70

Domain:

livingston.com

Telnet Access Port:

23

Loghost:

0.0.0.0

Maximum PMconsole:

1

Assigned Address:

0.0.0.0

RADIUS Server:

0.0.0.0

Alternate Server:

0.0.0.0

Accounting Server:

0.0.0.0

Alt. Acct. Server:

0.0.0.0

ISDN Switch Type:

NI-1

End Point Disc:

666600000000

Disabled Modules:

SNMP

To change the endpoint discriminator, use the set endpoint command, replacing Hex with any hexadecimal number up to 12 digits long:

Command> set endpoint Hex
Command> save all
Command> reboot

Note ¯ If you set the endpoint discriminator to a number less than 12 digits, the show global command output displays the number followed by as many zeros as needed to make a 12-digit number. For example, if you set the endpoint discriminator to 1, the show global command output displays the endpoint discriminator as 100000000000.

Dial-In Problems with Multichassis PPP

If a user cannot dial in to a PortMaster on a Multichassis PPP domain, a previous session for that user might still be running on the PortMaster. To display information about physical and virtual connections on a PortMaster, use the show sessions and show mcppp commands as described in the following sections.

If you find an active session for a user who has logged out, reset the session's port using the reset command:

Command> reset v0
Resetting port V0

Resetting a virtual port resets the corresponding physical port at the peer, as well. Resetting a physical port also resets the corresponding virtual port at the peer.

Displaying Port Usage Information

The show sessions command displays the current use of all ports. In the following example, the user hassan is connected to two physical ports and one virtual port corresponding to a physical port on a slave unit:

pm3> show sessions

 

 

 

Port

User

Host/Inet/Dest

Type

Dir

Status

Start

Idle

-----

------

-------------------

------

----

--------

-------

------

C0

-

-

Login

In

USERNAME

0

0

S0

hassan

174.154.32.35

Netwrk

In

ESTABLISHED

1:04

1:04

S1

hassan

174.154.32.35

Netwrk

In

ESTABLISHED

3

1:04

S2

 

 

Log/Net

In

NO-SERVICE

0

0

...

 

 

 

 

 

 

 

...

 

 

 

 

 

 

 

S23

 

 

Log/Net

In

NO-SERVICE

0

0

V0

hassan

174.154.32.35

Netwrk

In

ESTABLISHED

0

0

Displaying Multichassis PPP Information

The show mcppp command displays the IP addresses of PortMaster neighbors and any Multichassis PPP connections. The PortMaster in the following example has two neighbors (174.154.96.67 and 174.154.96.99) and one virtual connection for user hassan on port V0 with the physical port residing at the peer (174.154.96.67):

pm3> show mcppp

Neighbors:

 

 

 

174.154.96.67

 

 

 

 

174.154.96.99

 

 

 

 

Port

User

Host/Inet/Dest

Type

Peer

-----

-------

--------------

-------

--------

V0

hassan

174.154.32.35

VIRTUAL

174.154.96.67

Diagnosing a Hunt Group Rollover Problem

If the hunt group is failing to roll over on PRI line, use the following steps to determine if the problem originates at the telephone company rather than with the PortMaster:

  1. From a Telnet (not a terminal) command line session, attach to the S0 port.

    Command> attach s0
    Trying 192.168.1.1 ...

    Connected - Escape character is '^]'.

  2. Dial the PortMaster back into itself, replacing Number with the 7-digit telephone number of the PortMaster:

    atdtNumber
    Dialing...
    CONNECT 64000

    The PortMaster is now connected to its own S1 port.

  3. Login as !root and enter the administrative password:

    login: !root
    password: xxxxxx

  4. Ports S0 and S1 are now busy. Attach to the S2 port:

    Command> attach s2
    Trying 192.168.1.1 ...
    Connected - Escape character is '^]'.

  5. Dial the PortMaster back into itself:

    atdtNumber
    Dialing...
    CONNECT 64000

    The PortMaster is now connected to its own S3 port.

  6. Repeat this process until all interfaces are connected.
Use Table 4-2, if necessary, to identify the interfaces on your PortMaster.  
Table 4-2 PortMaster Interfaces

Line Type

Model or Circuit

Ports

T1 Primary Rate
Interface (PRI)

PM-3A-1T

PM-3A-2T

S0 through S23

S0 through S22
S24 through S46

E1 PRI

PM-3A-1E

PM-3A-2E

S0 through S29

S0 through S59

Channelized T1

One T1 circuit

Two T1 circuits

S0 through S23

S0 through S47

Channelized E1

One E1 circuit

Two E1 circuits

S0 through S29

S0 through S59

If the hunt group does not roll over to the next chassis, the telephone company has a problem with the provisioning. Contact your carrier for assistance.

Troubleshooting Compression

You can use the set debug ccp-lzs command to display Compression Control Protocol (CCP) information such as the allocation of compression data structures (called history slots), error messages, and reinitializations to the console. When compression is working, compression is freed and compression history slots are released when a user session is terminated, as shown in the following example:

Command> set console
Setting console to ADMIN session

Command> set debug ccp-lzs on

CCP 55230 for (S4) Pinahara slot 0
CCP 55230 freed by COMPORT S4
Releasing compression history slot 0



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