Using ppptrace
The ppptrace command traces the PPP frames as they are sent and received across the network. This information is the primary tool used to detect problems at the PPP link level.
See Appendix A, PPP Link Operation" for a detailed description of the various PPP frames and their significance.
The ppptrace command has the following general form:
prompt# ppptrace [--x] [ppp_link_name] |
To interpret the output from ppptrace completely, you need to be familiar with the operation of the Point-to-Point Protocol and the format of the various PPP frames. See Appendix A, PPP Link Operation for more information.
Tracing PPP Frames
When the ppptrace command is executed without arguments it displays a trace of all the active PPP links. You can restrict the trace by specifying an IP interface, or the link name you assigned to the link using the ppp_link_name parameter in the file ppp.conf.
To display a trace of the link associated with the IP interface ipdptp0, type:
prompt# ppptrace ipdptp0 |
To display a trace of the link associated with the link name ppplink0, type:
prompt# ppptrace ppplink0 |
The basic output from a typical ppptrace has the following components:
timestamp: link_id type: description [id: xx] [length: yyyy] |
timestamp
The time at which the trace was recorded.
link_id
Identifies the link from which the trace was recorded. This may be an IP interface name (ipdptpn or ipdn) or a link name assigned using the ppp_link_name parameter in the file ppp.conf.
type
Identifies the source of the frame, which may be either sent by the local host (outgoing), or received from the remote host (incoming).
description
Describes the PPP frame type. See Appendix A, PPP Link Operation for more information.
id: xx
The contents of the id field of the PPP frame, which carries an identifier that is used to match associated requests and replies. See Appendix A, PPP Link Operation for more information.
length: yyyy
The contents of the length field of the PPP frame, which carries the total length of the information field. The length must be less than the maximum receive unit (MRU). See Appendix A, PPP Link Operation for more information.
For example, the following trace shows an LCP Configure-request packet sent by the local host. The basic trace is followed by information that describes the frame in more detail, including the magic number, which identifies the initial source of the frame and is used to detect looped back conditions. See Appendix A, PPP Link Operation for more information.
18:10:32: ipdptp0 Send: LCP Packet Config Request [id: 15]
[length: 0012]
Maximun Receive unit: 1500
Magic Number: 4e0d20fb
Protocol Field Compression
Address and Control Field Compression
|
Displaying PPP Frame Contents
Executing the ppptrace command with the -x option dumps the contents of the PPP frames to display the hexadecimal codes.
To dump the contents of the PPP frames, type:
prompt# ppptrace -x 18:38:37: ipdptp0 Send: Internet Protocol Packet 21 45 00 00 54 86 e1 40 00 ff 01 58 9d 81 9d cc "!E..T..@...X...." 3d 81 9d cc b1 08 00 f9 4c 02 51 00 00 2f ba 26 "=.......L.Q../.&" 8d 00 01 bb 16 08 09 0a 0b 0c 0d 0e 0f 10 11 12 "................" 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f 20 21 22 "..............!"" 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f 30 31 32 "#$%&'()*+,-./012" 33 34 35 36 37 "34567 " |
The 21 at the beginning of the packet in this example indicates that it is an IP packet.
PPP Trace Examples
The following examples show how ppptrace can be used to detect and diagnose problems with a PPP link.
Trace Example 1--Successful Link Establishment
The following example trace shows an exchange of LPC and IPNCP packets that results in a PPP link established successfully between two hosts:
18:10:32: ipdptp0 Send: LCP Packet Config Request [id: 15] [length: 0012] Maximun Receive unit: 1500 Magic Number: 4e0d20fb Protocol Field Compression Address and Control Field Compression 18:10:32: ipdptp0 Recv: LCP Packet Config Request [id: 15] [length: 0012] Maximun Receive unit: 1500 Magic Number: 4e0d20fb Protocol Field Compression Address and Control Field Compression 18:10:32: ipdptp0 Recv: LCP Packet Config Request [id: 1c] [length: 0012] Maximun Receive unit: 1500 Magic Number: 17d1cf32 Protocol Field Compression Address and Control Field Compression 18:10:32: ipdptp0 Send: LCP Packet Config Request [id: 16] [length: 0012] Maximun Receive unit: 1500 Magic Number: 4e0d20fb Protocol Field Compression Address and Control Field Compression 18:10:32: ipdptp0 Send: LCP Packet Config Ack [id: 1c] [length: 0012] Maximun Receive unit: 1500 Magic Number: 17d1cf32 Protocol Field Compression Address and Control Field Compression 18:10:33: ipdptp0 Recv: LCP Packet Config Request [id: 1d] [length: 0012] Maximun Receive unit: 1500 Magic Number: 17d1cf32 Protocol Field Compression Address and Control Field Compression 18:10:33: ipdptp0 Send: LCP Packet Config Ack [id: 1d] [length: 0012] Maximun Receive unit: 1500 Magic Number: 17d1cf32 Protocol Field Compression Address and Control Field Compression 18:10:33: ipdptp0 Recv: LCP Packet Config Ack [id: 16] [length: 0012] Maximun Receive unit: 1500 Magic Number: 4e0d20fb Protocol Field Compression Address and Control Field Compression 18:10:33: ipdptp0 Send: NCP Packet Internet Protocol Config Request [id: 17] [length: 0010] IP Compression Protocol Van Jacobson IP Address: 129.157.204.61 18:10:33: ipdptp0 Recv: NCP Packet Internet Protocol Config Request [id: 1e] [length: 0010] IP Compression Protocol Van Jacobson IP Address: 129.157.204.177 18:10:33: ipdptp0 Send: NCP Packet Internet Protocol Config Ack [id: 1e] [length: 0010] IP Compression Protocol Van Jacobson IP Address: 129.157.204.177 18:10:33: ipdptp0 Recv: NCP Packet Internet Protocol Config Ack [id: 17] [length: 0010] IP Compression Protocol Van Jacobson IP Address: 129.157.204.61 |
Trace Example 2 -- Failed CHAP Negotiation
The following example trace shows the sequence of events that occur at the caller side, when the caller requests CHAP authentication from a peer that is not configured to support CHAP:
11:17:41: ipdptp0 Send: LCP Packet Config Request [id: 55] [length: 0012] Maximun Receive unit: 1500 Magic Number: ae36559a Protocol Field Compression Address and Control Field Compression 11:17:42: ipdptp0 Recv: LCP Packet Config Request [id: 55] [length: 0012] Maximun Receive unit: 1500 Magic Number: ae36559a Protocol Field Compression Address and Control Field Compression 11:17:42: ipdptp0 Recv: LCP Packet Config Request [id: 0e] [length: 0017] Maximun Receive unit: 1500 Authentication protocol: CHAP using MD5 algorithm Magic Number: 3ca14856 Protocol Field Compression Address and Control Field Compression 11:17:42: ipdptp0 Send: LCP Packet Config Reject [id: 0e] [length: 0009] Authentication protocol: CHAP using MD5 algorithm 11:17:42: ipdptp0 Recv: LCP Packet Terminate Request [id: 0f] [length: 0004] 11:17:42: ipdptp0 Send: LCP Packet Terminate Ack [id: 0f] [length: 0004] 11:17:45: ipdptp0 Send: LCP Packet Config Request [id: 56] [length: 0012] Maximun Receive unit: 1500 Magic Number: ae36559a Protocol Field Compression Address and Control Field Compression 11:17:48: ipdptp0 Send: LCP Packet Config Request [id: 57] [length: 0012] Maximun Receive unit: 1500 Magic Number: ae36559a Protocol Field Compression Address and Control Field Compression . . . 11:18:09: ipdptp0 Send: LCP Packet Config Request [id: 5f] [length: 0012] Maximun Receive unit: 1500 Magic Number: ae36559a Protocol Field Compression Address and Control Field Compression |
The following example trace shows the corresponding sequence of events that occur at the answering side:
18:28:21: ipdptp0 Send: LCP Packet Config Request [id: 20]
[length: 0017]
Maximun Receive unit: 1500
Authentication protocol: CHAP using MD5 algorithm
Magic Number: f16105df
Protocol Field Compression
Address and Control Field Compression
18:28:21: ipdptp0 Recv: LCP Packet Config Reject [id: 20]
[length: 0009]
Authentication protocol: CHAP using MD5 algorithm
18:28:21: ipdptp0 Send: LCP Packet Terminate Request [id: 21]
[length: 0004]
18:28:21: ipdptp0 Recv: LCP Packet Terminate Ack [id: 21]
[length: 0004]
|
Trace Example 3 -- Successful CHAP Negotiation
The following example trace shows the sequence of events that occur at the caller side, when CHAP authentication is negotiated successfully:
13:49:58: ipdptp0 Send: LCP Packet Config Request [id: 62] [length: 0012] Maximun Receive unit: 1500 Magic Number: 7bc9c0bb Protocol Field Compression Address and Control Field Compression 13:49:59: ipdptp0 Recv: LCP Packet Config Request [id: 62] [length: 0012] Maximun Receive unit: 1500 Magic Number: 7bc9c0bb Protocol Field Compression Address and Control Field Compression 13:49:59: ipdptp0 Recv: LCP Packet Config Request [id: 1b] [length: 0016] Maximun Receive unit: 1500 Authentication protocol: PAP Magic Number: 406bdebf Protocol Field Compression Address and Control Field Compression 13:49:59: ipdptp0 Send: LCP Packet Config Request [id: 63] [length: 0012] Maximun Receive unit: 1500 Magic Number: 7bc9c0bb Protocol Field Compression Address and Control Field Compression 13:49:59: ipdptp0 Send: LCP Packet Config Ack [id: 1b] [length: 0016] Maximun Receive unit: 1500 Authentication protocol: PAP Magic Number: 406bdebf Protocol Field Compression Address and Control Field Compression 13:49:59: ipdptp0 Recv: LCP Packet Config Request [id: 1c] [length: 0016] Maximun Receive unit: 1500 Authentication protocol: PAP Magic Number: 406bdebf Protocol Field Compression Address and Control Field Compression 13:49:59: ipdptp0 Send: LCP Packet Config Ack [id: 1c] [length: 0016] Maximun Receive unit: 1500 Authentication protocol: PAP Magic Number: 406bdebf Protocol Field Compression Address and Control Field Compression 13:49:59: ipdptp0 Recv: LCP Packet Config Ack [id: 63] [length: 0012] Maximun Receive unit: 1500 Magic Number: 7bc9c0bb Protocol Field Compression Address and Control Field Compression 13:49:59: ipdptp0 Send: PAP Packet Authenticate Request [id: 01] [length: 0010] Peer ID: 4e 41 4d 45 (NAME) Password: 50 41 53 53 57 44 (PASSWD) 13:49:59: ipdptp0 Recv: PAP Packet Authenticate Ack [id: 01] [length: 0005] No message 13:49:59: ipdptp0 Send: NCP Packet Internet Protocol Config Request [id: 64] [length: 0010] IP Compression Protocol Van Jacobson IP Address: 129.157.204.61 13:49:59: ipdptp0 Recv: NCP Packet Internet Protocol Config Request [id: 1d] [length: 0010] IP Compression Protocol Van Jacobson IP Address: 129.157.204.177 13:49:59: ipdptp0 Send: NCP Packet Internet Protocol Config Ack [id: 1d] [length: 0010] IP Compression Protocol Van Jacobson IP Address: 129.157.204.177 13:49:59: ipdptp0 Recv: NCP Packet Internet Protocol Config Ack [id: 64] [length: 0010] IP Compression Protocol Van Jacobson IP Address: 129.157.204.61 |
Trace Example 4 -- Dump of Successful ping
The following example trace shows a dump of the PPP frames exchanged during the successful execution of a ping(1M) command over an established PPP link:
18:38:37: ipdptp0 Send: Internet Protocol Packet 21 45 00 00 54 86 e1 40 00 ff 01 58 9d 81 9d cc "!E..T..@...X...." 3d 81 9d cc b1 08 00 f9 4c 02 51 00 00 2f ba 26 "=.......L.Q../.&" 8d 00 01 bb 16 08 09 0a 0b 0c 0d 0e 0f 10 11 12 "................" 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f 20 21 22 "..............!"" 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f 30 31 32 "#$%&'()*+,-./012" 33 34 35 36 37 "34567 " 18:38:37: ipdptp0 Recv: Internet Protocol Packet ff 03 00 21 45 00 00 54 ec 77 40 00 ff 01 f3 06 "...!E..T.w@....." 81 9d cc b1 81 9d cc 3d 00 00 01 4d 02 51 00 00 ".......=...M.Q.." 2f ba 26 8d 00 01 bb 16 08 09 0a 0b 0c 0d 0e 0f "/.&............." 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f "................" 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f ".!"#$%&'()*+,-./" 30 31 32 33 34 35 36 37 "01234567 " 18:38:38: ipdptp0 Send: Internet Protocol Packet 21 45 00 00 54 86 e2 40 00 ff 01 58 9c 81 9d cc "!E..T..@...X...." 3d 81 9d cc b1 08 00 3f 98 02 51 00 01 2f ba 26 "=......?..Q../.&" 8e 00 02 74 c8 08 09 0a 0b 0c 0d 0e 0f 10 11 12 "...t............" 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f 20 21 22 "..............!"" 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f 30 31 32 "#$%&'()*+,-./012" 33 34 35 36 37 "34567 " |
Trace Example 5 -- Dump of Successful telnet Session
The following example trace shows a dump of the PPP frames exchanged during the successful execution of a telnet(1) command over an established PPP link:
18:40:44: ipdptp0 Send: Internet Protocol Packet 21 45 00 00 2c 86 ee 40 00 ff 06 58 b3 81 9d cc "!E..,..@...X...." 3d 81 9d cc b1 80 35 00 17 94 b9 9a 00 00 00 00 "=.....5........." 00 60 02 22 38 2a be 00 00 02 04 05 b4 ".`."8*....... " 18:40:44: ipdptp0 Recv: Internet Protocol Packet ff 03 00 21 45 00 00 2c ec 84 40 00 ff 06 f3 1c "...!E..,..@....." 81 9d cc b1 81 9d cc 3d 00 17 80 35 93 e9 98 00 ".......=...5...." 94 b9 9a 01 60 12 22 38 fe c2 00 00 02 04 05 b4 "....`."8........" 18:40:44: ipdptp0 Send: VJ Uncompressed TCP/IP Packet 2f 45 00 00 28 86 ef 40 00 ff 00 58 b6 81 9d cc "/E..(..@...X...." 3d 81 9d cc b1 80 35 00 17 94 b9 9a 01 93 e9 98 "=.....5........." 01 50 10 22 38 16 80 00 00 ".P."8.... " 18:40:44: ipdptp0 Send: VJ Compressed TCP/IP Packet 2d 10 17 5c ff fd 03 ff fb 18 "-..\...... " 18:40:44: ipdptp0 Recv: VJ Uncompressed TCP/IP Packet ff 03 00 2f 45 00 00 28 ec 85 40 00 ff 00 f3 1f ".../E..(..@....." 81 9d cc b1 81 9d cc 3d 00 17 80 35 93 e9 98 01 ".......=...5...." 94 b9 9a 07 50 10 22 32 16 80 00 00 "....P."2.... " 18:40:45: ipdptp0 Recv: VJ Compressed TCP/IP Packet ff 03 00 2d 12 fe 70 06 ff fd 18 "...-..p.... " 18:40:45: ipdptp0 Send: VJ Compressed TCP/IP Packet 2d 0c 16 77 03 06 "-..w.. " 18:40:45: ipdptp0 Recv: VJ Compressed TCP/IP Packet ff 03 00 2d 1f 26 52 ff fb 03 ff fa 18 01 ff f0 "...-.&R........." 18:40:45: ipdptp0 Send: VJ Compressed TCP/IP Packet 2d 14 e4 8d 09 ff fa 18 00 53 55 4e 2d 43 4d 44 "-........SUN-CMD" ff f0 ".. " 18:40:45: ipdptp0 Recv: VJ Compressed TCP/IP Packet ff 03 00 2d 0c 16 61 0d 09 "...-..a.. " 18:40:46: ipdptp0 Recv: VJ Compressed TCP/IP Packet ff 03 00 2d 10 7f a0 ff fb 01 ff fd 01 0d 0a 0d "...-............" 0a 55 4e 49 58 28 72 29 20 53 79 73 74 65 6d 20 ".UNIX(r).System." 56 20 52 65 6c 65 61 73 65 20 34 2e 30 20 28 62 "V.Release.4.0.(b" 6c 6f 6e 64 65 29 0d 0a 0d 00 0d 0a 0d 00 "londe)........ " 18:40:46: ipdptp0 Send: VJ Compressed TCP/IP Packet 2d 1c 18 1d 37 0d ff fd 01 ff fc 01 "-...7....... " 18:40:46: ipdptp0 Recv: VJ Compressed TCP/IP Packet ff 03 00 2d 1c b4 01 06 37 6c 6f 67 69 6e 3a 20 "...-....7login:." 18:40:46: ipdptp0 Send: VJ Compressed TCP/IP Packet 2d 0c 16 1d 07 06 "-..... " 18:40:46: ipdptp0 Recv: VJ Compressed TCP/IP Packet ff 03 00 2d 1f 15 13 ff fe 01 "...-...... " 18:40:46: ipdptp0 Send: VJ Compressed TCP/IP Packet 2d 04 16 1a 03 "-.... " 18:40:53: ipdptp0 Send: VJ Compressed TCP/IP Packet 2d 10 a4 10 72 "-...r " 18:40:53: ipdptp0 Recv: VJ Compressed TCP/IP Packet ff 03 00 2d 1c a4 0f 01 03 72 "...-.....r " 18:40:53: ipdptp0 Send: VJ Compressed TCP/IP Packet 2d 0b 16 18 "-... " 18:40:54: ipdptp0 Send: VJ Compressed TCP/IP Packet 2d 10 a7 0e 6f "-...o " 18:40:54: ipdptp0 Recv: VJ Compressed TCP/IP Packet ff 03 00 2d 1b a7 0d 6f "...-...o " 18:40:54: ipdptp0 Send: VJ Compressed TCP/IP Packet 2d 0b 16 16 "-... " 18:40:54: ipdptp0 Send: VJ Compressed TCP/IP Packet 2d 10 a7 0c 6f "-...o " 18:40:54: ipdptp0 Recv: VJ Compressed TCP/IP Packet ff 03 00 2d 1b a7 0b 6f "...-...o " 18:40:55: ipdptp0 Send: VJ Compressed TCP/IP Packet 2d 0b 16 14 "-... " 18:40:55: ipdptp0 Send: VJ Compressed TCP/IP Packet 2d 10 a2 0a 74 "-...t " 18:40:56: ipdptp0 Recv: VJ Compressed TCP/IP Packet ff 03 00 2d 1b a2 09 74 "...-...t " 18:40:56: ipdptp0 Send: VJ Compressed TCP/IP Packet 2d 0b 16 12 "-... " 18:40:59: ipdptp0 Send: VJ Compressed TCP/IP Packet 2d 10 09 08 0d 00 "-..... " 18:40:59: ipdptp0 Recv: VJ Compressed TCP/IP Packet ff 03 00 2d 1c 08 fc 02 01 0d 0a "...-....... " 18:40:59: ipdptp0 Send: VJ Compressed TCP/IP Packet 2d 0b 16 0e "-... " 18:40:59: ipdptp0 Recv: VJ Compressed TCP/IP Packet ff 03 00 2d 1f 2e 33 50 61 73 73 77 6f 72 64 3a "...-..3Password:" 20 ". " 18:40:59: ipdptp0 Send: VJ Compressed TCP/IP Packet 2d 04 16 04 0a "-.... " 18:45:46: ipdptp0 Recv: Internet Protocol Packet ff 03 00 21 45 00 00 28 ec 92 40 00 ff 06 f3 12 "...!E..(..@....." 81 9d cc b1 81 9d cc 3d 00 17 80 35 93 e9 98 5e ".......=...5...^" 94 b9 9a 20 50 11 22 38 16 03 00 00 "....P."8.... " 18:45:46: ipdptp0 Send: VJ Compressed TCP/IP Packet 2d 04 16 03 01 "-.... " 18:45:46: ipdptp0 Send: Internet Protocol Packet 21 45 00 00 28 87 02 40 00 ff 06 58 a3 81 9d cc "!E..(..@...X...." 3d 81 9d cc b1 80 35 00 17 94 b9 9a 20 93 e9 98 "=.....5........." 5f 50 11 22 38 16 02 00 00 "_P."8.... " 18:45:46: ipdptp0 Recv: VJ Compressed TCP/IP Packet ff 03 00 2d 2c 16 02 01 0b 02 "...-,..... " |
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