Troubleshooting ISDN 1174_04F8_c1

Thierry Martens tmartens@cisco.com

What You Should Know BRI T1 and E1 PRI ISDN protocol architecture

Basic Rate Access (BRI) 2B + D S0 interface B-CHANNEL BRI 2 B channels at 64 kbps each 1 D channel at 16 kbps Framing and synchronization at 48 kbps Total speed 192 kbps Intended to be used at small concentration points Referred to as S0 interface B-CHANNEL D-CHANNEL

T1 Primary Rate Interface (PRI) T1 PRI or S1 interface Used in North America and Japan 23 B + D B-CHANNEL T1-PRI 23 B channels at 64 kbit/s 1 D channel at 64 kbit/s Framing and synchronization at 8 kbit/s Total speed 1544 kbit/s D-CHANNEL

E1 Primary Rate Interface (PRI) E1 PRI or S2 interface Used in Europe 30 B + D B-CHANNEL E1-PRI 30 B channels at 64 kbit/s 1 D channel at 64 kbit/s Framing and synchronization at 64 kbit/s Total speed 2048 kbit/s D-CHANNEL

ISDN Protocol Architecture B-Channel D-Channel IP, … Q.931 Network Network PPP LAPD–Q.921 Data Link Data Link I.430 (BRI)–I.431 (PRI) Physical Physical

Troubleshooting ISDN “There are only two possible problems with ISDN: The first problem occurs when you try to install it The second problem occurs when you receive the first invoice”

Troubleshooting ISDN Be systematic Go step by step Always troubleshoot both ends of the connection

Troubleshooting Menu Troubleshooting Ping remote int Debug dialer Sh isdn stat Layer 1 Layer 2 Layer 3 Debug PPP LCP Speed 56/64 Pap/chap NCP Ping remote net Tune cost

Ping Remote ISDN Int Troubleshooting Ping remote int Ping remote net Tune cost ping 1.1.1.1 ping 1.1.1.2 ISDN 1.1.1.1 1.1.1.2 Do not bother to look at routing or cost issues if that doesn’t work

Debug Dialer router# debug dialer events Troubleshooting Ping remote int Debug dialer Sh isdn stat Debug PPP Ping remote net Tune cost router# debug dialer events Dialing cause: BRI0: ip (s=172.16.1.111 d172.16.2.22) router# debug dialer packets BRI0: ip (s=10.1.1.8, d=10.1.1.1),100 bytes, interesting (ip PERMIT)

SH ISDN Status router#sh isdn stat ISDN BRI0 interface Layer 1 Status: Troubleshooting Ping remote int Debug dialer Sh isdn stat Layer 1 Layer 2 Layer 3 Debug PPP Ping remote net Tune cost router#sh isdn stat ISDN BRI0 interface Layer 1 Status: DEACTIVATED Layer 2 Status: Layer 2 NOT Activated Layer 3 Status: No Active Layer 3 Call(s) Activated dsl 0 CCBs are 0, Allocated = 0 New command included around 10.2(3)

TDM Multiplexing Creates B1, B2, and D channels Troubleshooting Ping remote int Debug dialer Sh isdn stat Layer 1 Layer 2 Layer 3 Debug PPP Ping remote net Tune cost Creates B1, B2, and D channels 48-bit physical frame, 4000 frames/s, 192 kbps 2 x 8 B1 bits, 2 x 8 B2 bits, 4 x 1 D bit 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 B B B B B B B B F N B B B B B B B B B B B B B B B B B B B B B B B B F D D D D 1 1 1 1 1 1 1 1 A 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 Frame from NT to TE 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 B B B B B B B B F B B B B B B B B B B B B B B B B B B B B B B B B F D D D D 1 1 1 1 1 1 1 1 A 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 Frame from TE to NT

Synchronization 1st Line Code Violation 2nd Line Code Violation F Troubleshooting Ping remote int Debug dialer Sh isdn stat Layer 1 Layer 2 Layer 3 Debug PPP Ping remote net Tune cost F 1st Line Code Violation 2nd Line Code Violation 1 2 3 4 Each frame starts with a double line code violation (binary 0 coded with same polarity as previous 0) F bit (always 0) creates first violation First data 0 or FA or N bit (one of them always 0) create second violation The start of every physical frame is marked by a valid pair of line code violations. F bit and first data 0 F bit and FA bit (bit 14 - TE to NT direction) F bit and FA or N bit (bit 14 or 15 - NT to TE direction) A pair of line code violations is called valid if both violations are separated by maximum : 13 bittimes in TE to NT direction 14 bittimes in NT to TE direction As soon as 3 successive valid pairs of line code violations are detected, a device will assume that synchronization is achieved As soon as no valid pair of line code violations is detected in two successive physical ISDN frames, synchronization is lost 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 B B B B B B B B F N B B B B B B B B B B B B B B B B B B B B B B B B F D D D D 1 1 1 1 1 1 1 1 A 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 Frame from NT to TE 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 B B B B B B B B F B B B B B B B B B B B B B B B B B B B B B B B B F D D D D 1 1 1 1 1 1 1 1 A 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 Frame from TE to NT

Activation (A Bit) A=0: Deactivated A=1: Activated Troubleshooting Ping remote int Debug dialer Sh isdn stat Layer 1 Layer 2 Layer 3 Debug PPP Ping remote net Tune cost A=0: Deactivated A=1: Activated 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 B B B B B B B B F N B B B B B B B B B B B B B B B B B B B B B B B B F D A D D D 1 1 1 1 1 1 1 1 A 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 Frame from NT to TE 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 B B B B B B B B F B B B B B B B B B B B B B B B B B B B B B B B B F D D D D 1 1 1 1 1 1 1 1 A 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 Frame from TE to NT

Activation Procedure: INFO 0 TE NT 1– INFO 0–Not Active: No Signal No Signal No Signal TE states state F1 : inactive state F2 : sensing (after power up) state F3 : deactivated state F4 : awaiting signal (waiting for info 2) state F5 : identifying input (info 2 or info 4) state F6 : synchronized (waiting for info 4) state F7 : activated state F8 : lost framing

Activation Procedure: INFO 1 TE NT 1– INFO 0–Not Active: No Signal No Signal No Signal 2– INFO 1–TE becomes Active: "01111110" Signal (= HDLC Flags) TE states state F1 : inactive state F2 : sensing (after power up) state F3 : deactivated state F4 : awaiting signal (waiting for info 2) state F5 : identifying input (info 2 or info 4) state F6 : synchronism (waiting for info 4) state F7 : activated state F8 : lost framing

Activation Procedure: INFO 2 TE NT 1– INFO 0–Not Active: No Signal No Signal No Signal 2– INFO 1–TE becomes Active: "01111110" Signal (= HDLC Flags) 3– INFO 2–Network Sends Frames with A-bit = 0 F A=0 TE states state F1 : inactive state F2 : sensing (after power up) state F3 : deactivated state F4 : awaiting signal (waiting for info 2) state F5 : identifying input (info 2 or info 4) state F6 : synchronized (waiting for info 4) state F7 : activated state F8 : lost framing

Activation Procedure: INFO 3 TE NT 1– INFO 0–Not Active: No Signal No Signal No Signal 2– INFO 1–TE becomes Active: "01111110" Signal (= HDLC Flags) 3– INFO 2–Network Sends Frames with A-bit = 0 F A=0 TE states state F1 : inactive state F2 : sensing (after power up) state F3 : deactivated state F4 : awaiting signal (waiting for info 2) state F5 : identifying input (info 2 or info 4) state F6 : synchronized (waiting for info 4) state F7 : activated state F8 : lost framing 4– INFO 3–TE Synchronizes and Sends Physical Frames F

Activation Procedure: INFO 4 TE NT 1– INFO 0–Not Active: No Signal No Signal No Signal 2– INFO 1–TE becomes Active: "01111110" Signal (= HDLC Flags) 3– INFO 2–Network Sends Frames with A-bit = 0 F A=0 TE states state F1 : inactive state F2 : sensing (after power up) state F3 : deactivated state F4 : awaiting signal (waiting for info 2) state F5 : identifying input (info 2 or info 4) state F6 : synchronized (waiting for info 4) state F7 : activated state F8 : lost framing 4– INFO 3–TE Synchronizes and Sends Physical Frames F 5–INFO 4–NT Synchronizes and Sends Frames with A-bit = 1 F A=1

Debug BRI: Activation :24: BRI: write_sid: scp = 0, wrote = 1B SID interrupt. status reg = C 23:57:24: BRI: Received activation indication… 23:57:26: BRI: write_sid: scp = 0, wrote = E

Debug BRI: T3 Timer Expires BRI: Starting Power Up timer for unit = 2 BRI: write_sid: wrote 3 for subunit 2, slot 1 BRI: Starting T3 timer after expiry of Power Up timeout for unit = 2, current state is F4 (…) BRI: write_sid: wrote 92 for subunit 2, slot 1 BRI: write_sid: wrote 93 for subunit 2, slot 1 BRI: T3 timer expired for unit = 2, current state is F2 BRI: write_sid: wrote 1 for subunit 2, slot 1 BRI: write_sid: wrote 0 for subunit 2, slot 1 BRI: Forced interrupt for subunit 2, slot 1 is F BRI: write_sid: wrote FF for subunit 2, slot 1 BRI: Deactivation for unit = 2, current state is F2 Timer T3 maximum 30 s.

SH CONT BRI 0 router#sh cont bri BRI unit 0 D Chan Info: Layer 1 is Activated Idb 0x9F6E8, ds 0xA56F8, reset_mask 0x8 buffer size 1524 RX ring with 2 entries at 0x2101600: Rxhead 0 00 pak=0x0AB0A4 ds=0x40CE70 status=D000 pak_size=0 (…)

PRI: SH CONT: No Alarms sh cont t1 T1 2/0 is up Description: Primary Rate Interface to DMS-100 No alarms detected Framing is ESF, Line Code is B8ZS, Clock Source is Line Data in current interval (165 seconds elapsed): 0 Line Code Violations, 0 Path Code Violations 0 Slip Secs, 1 Fr Loss Secs, 0 Line Err Secs, 0 Degraded Mins 0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 12 Unavail Secs

PRI: SH CONT: Alarms sh cont t1 T1 2/1 is down Transmitter is sending remote alarm Receiver has loss of signal Framing is ESF, Line Code is B8ZS, Clock Source is Line Data in current interval (160 seconds elapsed): 0 Line Code Violations, 0 Path Code Violations 0 Slip Secs, 0 Fr Loss Secs, 0 Line Err Secs, 0 Errored Secs, 0 Bursty Err Secs, 0 Severely Err Secs, 160 Unavail Secs

SH ISDN Status router#sh isdn stat Troubleshooting Ping remote int Debug dialer Sh isdn stat Layer 1 Layer 2 Layer 3 Debug PPP Ping remote net Tune cost router#sh isdn stat The current ISDN Switchtype = basic-net3 ISDN BRI0 interface Layer 1 Status: Activated Layer 2 Status: Layer 2 NOT Activated Layer 3 Status: No Active Layer 3 Call(s) Activated dsl 0 CCBs are 0, Allocated = 0

ISDN Protocol Architecture B-Channel D-Channel IP, … Q.931 Network Network PPP LAPD–Q.921 Data Link Data Link I.430 (BRI)–I.431 (PRI) Physical Physical

Q.921–LAPD TE ET The Data Link Layer The ISDN network does not impose the use of any data link layer protocol for the B channels On the D channel the use of Q.921 or LAPD is defined LAPD: Link Access Procedure on the D channel Specified in CCITT I.441 and Q.921 Q.921 protocol is used between the TE and the local ISDN switch (not end-to-end) Q.921–LAPD TE ET NT1 LT 1174_04F8_c1 29

TEI Assignment TE sends ID REQ, switch answers with ID ASSN AI = 127 asks for any TEI AI = 64 means TEI 64 is assigned Reference Indicator (RI) is a random number RI must match in request and response ID Request (AI = 127 , RI = 23) ID Assigned (AI = 64 , RI = 23) TE ET

Debug ISDN Q921: TEI Assigned TEI 64 gets assigned by the switch 2656.612 TX -> IDREQ ri = 14613 ai = 127 2656.648 RX <- IDASSN ri = 14613 ai = 64

Debug ISDN Q921: No TEI IDREQ gets retransmitted Timer T202 (default 2 seconds) Every IDREQ has a different RI 2424.920 TX -> IDREQ ri = 63529 ai = 127 2426.924 TX -> IDREQ ri = 31418 ai = 127 2428.928 TX -> IDREQ ri = 9819 ai = 127 Could point to the fact that the switch is expecting TEI = 0 In Europe ask point-to-multipoint In US ask point-to-point

Connection Establishment The TE or the switch send an SABME to establish the data link connection SABME needs to be acknowledged by an UA SABME (SAPI=0 , TEI=64) TE ET UA (SAPI=0 , TEI=64)

Debug ISDN Q921: Connection You need a TEI before you can send an SABME SAPI=0 means this data link will be used for signaling 2656.612 TX -> IDREQ ri = 14613 ai = 127 2656.648 RX <- IDASSN ri = 14613 ai = 64 2656.652 TX -> SABMEp sapi = 0 tei = 64 2656.676 RX <- UAf sapi = 0 tei = 64

Information Transfer Once the data link connection is established, INFO frames can be exchanged INFO frames get acknowledged by other INFO frames or by RR frames INFO (SAPI=0 , TEI=64 , N(S)=0 , N(R)=0) TE ET INFO (SAPI=0 , TEI=64 , N(S)=0 , N(R)=1) RR (SAPI=0 , TEI=64 , N(R)=1)

Debug ISDN Q921: INFO 2656.612 TX -> IDREQ ri = 14613 ai = 127 2656.648 RX <- IDASSN ri = 14613 ai = 64 2656.652 TX -> SABMEp sapi = 0 tei = 64 2656.676 RX <- UAf sapi = 0 tei = 64 2658.360 RX <- INFOc sapi = 0 tei = 64 ns = 0 nr = 0 2658.368 TX -> RRr sapi = 0 tei = 64 nr = 1 2658.372 TX -> INFOc sapi = 0 tei = 64 ns = 0 nr = 1

Data Link Monitor If no INFO frames are exchanged, the status of the data link can be checked by the periodic exchange of RR frames This procedure is optional RR (SAPI=0 , TEI=64 , N(R)=3) TE ET RR (SAPI=0 , TEI=64 , N(R)=7)

Debug ISDN Q921: RR 180484 RX <- RRp sapi = 0 tei = 80 nr = 5 180488 TX -> RRf sapi = 0 tei = 80 nr = 4 190484 RX <- RRp sapi = 0 tei = 80 nr = 5 190488 TX -> RRf sapi = 0 tei = 80 nr = 4 200484 RX <- RRp sapi = 0 tei = 80 nr = 5 200488 TX -> RRf sapi = 0 tei = 80 nr = 4 210484 RX <- RRp sapi = 0 tei = 80 nr = 5 210484 TX -> RRf sapi = 0 tei = 80 nr = 4

Sh ISDN Stat Layer 1 Status: ACTIVE Layer 2 Status: Troubleshooting Ping remote int Debug dialer Sh isdn stat Layer 1 Layer 2 Layer 3 Debug PPP Ping remote net Tune cost Layer 1 Status: ACTIVE Layer 2 Status: TEI = 0, State = MULTIPLE_FRAME_ESTABLISHED Layer 3 Status: 0 Active Layer 3 Call(s) Activated dsl 0 CCBs = 0

ISDN Protocol Architecture B-Channel D-Channel IP, … Q.931 Network Network PPP LAPD–Q.921 Data Link Data Link I.430 (BRI)–I.431 (PRI) Physical Physical

Q.931 TE ET The Network Layer The ISDN network does not impose the use of any network link layer protocol for the B channels On the D channel the use of Q.931 is defined Q.931 protocol is used between the TE and the local ISDN switch (not end-to-end!) Inside the ISDN network SS#7 ISUP is used Q.931 TE ET NT1 LT 1174_04F8_c1 41

ISDN Switch Type Q.931 comes in many local flavors Use the ISDN switch-type command to specify the correct version of the protocol basic 1tr6 - ntt basic-5ess - primary-4ess basic-dms100 - primary-5ess basic-net3 - primary-dms100 basic-ni1 - primary-net5 basic-nwnet3 - vn2 basic-nznet3 - vn3 basic-ts013

Call Setup En-bloc sending: the initial set-up message contains all necessary addressing information Setup Setup TE ET ET TE Call Proceeding Connect Connect Connect ACK

Debug ISDN Q931: Outgoing Call 248236 TX -> INFOc sapi = 0 tei = 80 ns = 6 nr = 6 SETUP pd = 8 callref = 0x02 Bearer Capability i = 0x8890 Channel ID i = 0x83 Called Party Number i = 0x80, '372756' 248392 RX <- INFOc sapi = 0 tei = 80 ns = 6 nr = 7 CALL_PROC pd = 8 callref = 0x82 Channel ID i = 0x89 249460 RX <- INFOc sapi = 0 tei = 80 ns = 7 nr = 7 CONNECT pd = 8 callref = 0x82

Debug ISDN Q93: Incoming Call 251076 RX <- UI sapi = 0 tei = 127 SETUP pd = 8 callref = 0x45 Bearer Capability i = 0x8890 Channel ID i = 0x8A Calling Party Number i = 0x0083, '372500' Calling Party SubAddr i = 0x80, 'P2902' Called Party Number i = 0x 251564 TX -> INFOc sapi = 0 tei = 80 ns = 8 nr = 8 CONNECT pd = 8 callref = 0xC5 251996 RX <- INFOc sapi = 0 tei = 80 ns = 8 nr = 9 CONNECT_ACK pd = 8 callref = 0x45

SPIDS Service Profile Identifier Used to bind a specific terminal to a specific service profile (only on BRI) SPIDS are assigned by the service provider SPID is 10 digit telephone number + extra digits DMS-100 and NI-1 require SPIDS Do not use SPIDS unless you have to SPIDS are only used in North America

SPIDS: Configuration Isdn spid1 spid-number (ldn) Assigned by service provider Usually ten digit telephone number + some extra digits ldn: local directory number Optional Required to receive incoming calls on the second B Channel

SPIDS: Configuration Examples Isdn spid1 415555836201 5558362 Isdn spid2 415555837002 5558370 Spid-number: 415: area code 555: exchange 8362 and 8370: station ID 01 and 02: terminal identifier ldn: local directory number

SPID Validation SPIDS are validated by the switch Handshake between TE and local ISDN switch Valid SPID is acknowledged with Endpoint ID INFO (SPID = SPID1) TE ET INFO (ENDPOINT IDENT) INFO (SPID = SPID2) INFO (ENDPOINT IDENT)

Debug ISDN Q931: Valid SPIDS 11438.776 TX -> INFORMATION pd = 8 callref = (null) SPID Information i = 0x363133373835323631323030 11438.872 RX <- INFORMATION pd = 8 callref = (null) ENDPOINT IDent i = 0xF180 11443.848 TX -> INFORMATION pd = 8 callref = (null) SPID Information i = 0x363133373835323631333030 11443.972 RX <- INFORMATION pd = 8 callref = (null) ENDPOINT IDent i = 0xF080

INFO (Invalid IE Contents) INFO (Invalid IE Contents) Invalid SPIDS Rejected by the network INFO (SPID = SPID1) TE ET INFO (Invalid IE Contents) INFO (SPID = SPID2) INFO (Invalid IE Contents)

Debug ISDN Q931: Incorrect SPID 11678.060 TX -> INFORMATION pd = 8 callref = (null) SPID Information i = 0x31323334353536373736 11678.164 RX <- INFORMATION pd = 8 callref = (null) Cause i = 0x82E43A–Invalid IE contents

SH ISDN Stat Layer 1 Status: Layer 2 Status: Spid Status: ACTIVE Layer 2 Status: TEI = 88, State = MULTIPLE_FRAME_ESTABLISHED Spid Status: TEI 88, ces = 1, state = 6(not initialized) spid1 configured, no LDN, spid1 sent, spid1 NOT valid TEI Not Assigned, ces = 2, state = 1(terminal down) spid2 configured, no LDN, spid2 NOT sent, spid2 NOT valid Layer 3 Status: 0 Active Layer 3 Call(s) Activated dsl 1 CCBs = 0

Call Refused Call can be refused for various reasons Setup Setup TE ET ET TE Release Complete Release Complete

Debug ISDN Q93: Call Refused 0:03:10: 190.680 TX -> SETUP pd = 8 callref = 0x01 0:03:10: Bearer Capability i = 0x8890 0:03:10: Channel ID i = 0x83 0:03:10: Called Party Number i = 0x80, '4839625' 0:03:10: 190.756 RX <- RELEASE_COMP pd = 8 callref = 0x81 0:03:10: Cause i = 0x8295 - Call rejected

Call Clearing Any side can clear the call Disconnect Disconnect TE ET ET TE Release Release Release Complete Release Complete

Debug ISDN Q931: Call Cleared 312.900 RX <- INFOc sapi = 0 tei = 96 ns = 1 nr = 2 DISCONNECT pd = 8 callref = 0x81 Cause i = 0x82D8 Signal i = 0x03 312.912 TX -> RRr sapi = 0 tei = 96 nr = 2 received HOST_DISCONNECT_ACK 312.920 TX -> INFOc sapi = 0 tei = 96 ns = 2 nr = 2 RELEASE pd = 8 callref = 0x01 Cause i = 0x8090 312.948 RX <- RRr sapi = 0 tei = 96 nr = 3 313.220 RX <- INFOc sapi = 0 tei = 96 ns = 2 nr = 3 RELEASE_COMP pd = 8 callref = 0x81

Show ISDN Status Layer 1 Status: ACTIVE Layer 2 Status: Troubleshooting Ping remote int Debug dialer Sh isdn stat Layer 1 Layer 2 Layer 3 Debug PPP Ping remote net Tune cost Layer 1 Status: ACTIVE Layer 2 Status: TEI = 0, State = MULTIPLE_FRAME_ESTABLISHED Layer 3 Status: 6 Active Layer 3 Call(s) Activated dsl 0 CCBs = 6 CCB:callid=8020, sapi=0, ces=0, B-chan=22 CCB:callid=8026, sapi=0, ces=0, B-chan=20 CCB:callid=8027, sapi=0, ces=0, B-chan=18 CCB:callid=8029, sapi=0, ces=0, B-chan=23 CCB:callid=A02D, sapi=0, ces=0, B-chan=21 CCB:callid=A030, sapi=0, ces=0, B-chan=19 Total Allocated ISDN CCBs = 6

ISDN Protocol Architecture B-Channel D-Channel IP, … Q.931 Network Network PPP LAPD–Q.921 Data Link Data Link I.430 (BRI)–I.431 (PRI) Physical Physical

Point-to-Point Protocol Troubleshooting Ping remote int Debug dialer Sh isdn stat Layer 1 Layer 2 Layer 3 Debug PPP Ping remote net Tune cost PPP: RFC 1548 + others Three main components of PPP Multiprotocol encapsulation Link Control Protocol (LCP) Establishing and maintaining the data link Option negotiation (e.g. use CHAP) Several Network Control Protocols (NCP) Establishing and configuring network layer protocols Protocol specific option negotiation (addresses, …) IPCP, IPXCP ATCP, …

LCP Negotiation Configure-Req proposes certain options Troubleshooting Ping remote int Debug dialer Sh isdn stat Debug PPP LCP Speed 56/64 Pap/chap NCP Ping remote net Tune cost Configure-Req proposes certain options If all options are acceptable, the remote station returns a Configure-ACK Configure-Req Configure-ACK

LCP Negotiation In reality all PPP negotiations are double negotiations Configure-Req Configure-ACK Configure-Req Configure-ACK

Debug PPP Packet: LCP ACK PPP BRI: B-Channel 1: I LCP CONFREQ(1) id 2 (4) PPP BRI: B-Channel 1: O LCP CONFACK(2) id 2 (4)

Debug PPP Negotiation ppp: sending CONFREQ, type = 3 (CI_AUTHTYPE), value = C023/0 ppp: sending CONFREQ, type = 5 (CI_MAGICNUMBER), value = 8C01B4 ppp: config ACK received, type = 3 (CI_AUTHTYPE), value = C023 ppp: config ACK received, type = 5 (CI_MAGICNUMBER), value = 8C01B4 1174_04F8_c1 64

SH INT BRI 0 1 BRI0: B-Channel 1 is up, line protocol is up Hardware is BRI MTU 1500 bytes, BW 64 Kbit, DLY 20000 usec, rely 255/255, load 1/255 Encapsulation PPP, loopback not set, keepalive set (10 sec) lcp state = OPEN ncp ipcp state = REQSENT ncp osicp state = NOT NEGOTIATED ncp ipxcp state = NOT NEGOTIATED ncp xnscp state = NOT NEGOTIATED ncp vinescp state = NOT NEGOTIATED ncp deccp state = NOT NEGOTIATED ncp bridgecp state = NOT NEGOTIATED ncp atalkcp state = NOT NEGOTIATED Last input 0:00:00, output 0:00:00, output hang never Last clearing of "show interface" counters never Output queue 0/40, 0 drops; input queue 0/75, 0 drops Five minute input rate 0 bits/sec, 0 packets/sec Five minute output rate 0 bits/sec, 1 packets/sec 9099 packets input, 855915 bytes, 0 no buffer (…) Troubleshooting Ping remote int Debug dialer Sh isdn stat Debug PPP LCP Speed 56/64 Pap/chap NCP Ping remote net Tune cost

64 and 56 kbps Inter-switch connections may limit the speed to 56 kbps Troubleshooting Ping remote int Debug dialer Sh isdn stat Debug PPP LCP Speed 56/64 Pap/chap NCP Ping remote net Tune cost Inter-switch connections may limit the speed to 56 kbps The bearer capability can specify that the call is a 56 kbps call that uses V.110 rate adaptation If the internal signalling protocol in the ISDN network is adapted to ISDN (SS#7 ISUP) this 56 kbps indication will carried up till the remote subscriber Setup(56) (56) Setup(56) TE ET ET TE

64 and 56 kbps The dialer map allows you to specify the speed for the outgoing call Dialer map ip 1.1.1.1 123456 speed 56 Default is 64 kbps Setup(56) (56) Setup(56) TE ET ET TE

Call Not End-to-End ISDN Many (international) ISDN connections do not yet use full ISDN signaling in the network The consequence is that the 56 kbps indication is not passed to the remote switch Setup(56) (56) Setup(64) TE ET ET TE Not End-to-End ISDN The receiving side thinks a 64 kbit/s call The only indication is that the call is not end-to-end isdn. You can configure isdn not-end-to-end 56

Debug ISDN Q931 17993.584 TX -> SETUP pd = 8 callref = 0x02 Troubleshooting Ping remote int Debug dialer Sh isdn stat Debug PPP LCP Speed 56/64 Pap/chap NCP Ping remote net Tune cost 17993.584 TX -> SETUP pd = 8 callref = 0x02 Bearer Capability i = 0x8890 Channel ID i = 0x83 Called Party Number i = 0x80, '97832480' 17993.820 RX <- CALL_PROC pd = 8 callref = 0x82 Channel ID i = 0x89 Locking Shift to Codeset 5 Codeset 5 IE 0x2A i = 0x808E0C, 'OUTSIDE CALL' 17994.696 RX <- PROGRESS pd = 8 callref = 0x82 Progress Ind i = 0x8A81 - Call not end-to-end ISDN 17996.648 RX <- CONNECT pd = 8 callref = 0x82 Progress Ind i = 0x8482 - Destination address is non-ISDN

PAP and CHAP Authentication protocols Troubleshooting Ping remote int Debug dialer Sh isdn stat Debug PPP LCP Speed 56/64 Pap/chap NCP Ping remote net Tune cost Authentication protocols PAP: Password Authentication Protocol CHAP: Challenge Handshake Authentication Protocol CHAP is to be preferred over PAP

Configuration CHAP ISDN Router Left Router Right hostname left username right password cisco int bri 0 encapsulation ppp ppp authentication chap ip add 1.0.0.1 255.255.255.0 dialer map ip 1.0.0.2 name right 12345 hostname right username left password cisco int bri 0 encapsulation ppp ppp authentication chap ip add 1.0.0.2 255.255.255.0 dialer map ip 1.0.0.1 name left 54321 Passwords must be identical at both ends Router name and password are case sensitive ISDN Router Left Router Right 1174_04F8_c1 71

Debug PPP CHAP ISDN Event: Connected to 2823680 on B1 at 64 kbps BRI0: B-Channel 1: PPP AUTH CHAP input code = 1 id = 10 len = 14 BRI0: B-Channel 1: PPP AUTH CHAP input code = 2 id = 16 len = 26 BRI0: B-Channel 1: remote passed CHAP authentication BRI0: B-Channel 1: PPP AUTH CHAP input code = 3 id = 10 len = 4 BRI0: B-Channel 1: Passed CHAP authentication with remote… CHAP code fields : 1 Challenge 2 Response 3 Success 4 Failure

SH DIALER brussels# sh dial BRI0 - dialer type = ISDN Dial String Successes Failures Last called Last status 4085261234 0 0 never 0 incoming call(s) have been screened BRI0: B-Channel 1 - dialer type = ISDN Rotary group 0, priority = 0 Idle timer (120 secs), Fast idle timer (20 secs) Wait for carrier (30 secs), Re-enable (15 secs) Time until disconnect 85 secs Connected to 4085261234 (dallas) If sh dialer displays the name of the remote router, it means we passed pap or chap authentication

The Prefix Issue Without PAP or CHAP With PAP or CHAP Router Right 54321 Not Yet Connected Router Left Router Right 54321 1st Call (from 40854321) 2nd Call (to 54321) 54321 12345 With PAP or CHAP Left Already Connected Router Left Router Right 54321 Call (from 40854321) 54321 12345

The Prefix Issue PAP/CHAP enable you to know which site is connected Troubleshooting Ping remote int Debug dialer Sh isdn stat Debug PPP LCP Speed 56/64 Pap/chap NCP Ping remote net Tune cost PAP/CHAP enable you to know which site is connected Without PAP or CHAP, this would be based on the ISDN calling number. This is often problematic Calling number may not been presented Calling number may be presented with/ without prefixes The net result is that without PAP or CHAP you would open two half-duplex B channels (instead of one full duplex)

NCP Network control protocols Troubleshooting Ping remote int Debug dialer Sh isdn stat Debug PPP LCP Speed 56/64 Pap/chap NCP Ping remote net Tune cost Network control protocols Negotiate and verify network level parameters (address) Different NCP for the different network protocols (IPCP, IPXCP, …) NCP Configure-req NCP Configure-ACK

Debug PPP Negotiation BRI0: B-Channel 1: O IPCP CONFREQ id D (10) Type3 (6) 147 211 117 40 BRI0: B-Channel 1: I IPCP CONFREQ id C (10) Type3 (6) 147 211 117 1 BRI0: B-Channel 1: O IPCP CONFACK id C (10) Type3 (6) 147 211 117 1 BRI0: B-Channel 1: I IPCP CONFACK id D (10) Type3 (6) 147 211 117 40

SH INT BRI 0 1 BRI0: B-Channel 1 is up, line protocol is up Troubleshooting Ping remote int Debug dialer Sh isdn stat Debug PPP LCP Speed 56/64 Pap/chap NCP Ping remote net Tune cost BRI0: B-Channel 1 is up, line protocol is up Hardware is BRI MTU 1500 bytes, BW 64 Kbit, DLY 20000 usec, rely 255/255, load 1/255 Encapsulation PPP, loopback not set, keepalive set (10 sec) lcp state = OPEN ncp ipcp state = OPEN ncp osicp state = NOT NEGOTIATED ncp ipxcp state = REQSENT ncp xnscp state = NOT NEGOTIATED (…)

SH INT BRI 0 1 BRI0: B-Channel 1 is up, line protocol is up Troubleshooting Ping remote int Debug dialer Sh isdn stat Debug PPP LCP Speed 56/64 Pap/chap NCP Ping remote net Tune cost BRI0: B-Channel 1 is up, line protocol is up Hardware is BRI MTU 1500 bytes, BW 64 Kbit, DLY 20000 usec, rely 255/255, load 1/255 Encapsulation PPP, loopback not set, keepalive set (10 sec) lcp state = OPEN ncp ipcp state = OPEN (…)

ISDN Protocol Architecture B-Channel D-Channel IP, … Q.931 Network Network PPP LAPD–Q.921 Data Link Data Link I.430 (BRI)–I.431 (PRI) Physical Physical

Ping Remote Networks Troubleshooting Ping remote int Debug dialer Sh isdn stat Debug PPP Ping remote net Tune cost ping 2.2.2.2 from 3.3.3.3 ping 3.3.3.3 from 2.2.2.2 ISDN 1.1.1.1 1.1.1.2 2.2.2.2 3.3.3.3 Now that we can ping the remote ISDN interface, we can look at routing issues

Static or Dynamic Routes Static routes are most often used Dynamic routes risk to bring up the lines all the time If you use dynamic routes, make sure broadcast updates are forwarded over ISDN Snapshot routing is best suited dynamic solution ip route 170.11.12.0 255.255.255.0 170.11.18.1

Don’t Wait for the First Bill Troubleshooting Ping remote int Debug dialer Sh isdn stat Debug PPP Ping remote net Tune cost ping 2.2.2.2 from 3.3.3.3 ping 3.3.3.3 from 2.2.2.2 ISDN 1.1.1.1 1.1.1.2 2.2.2.2 3.3.3.3

Interesting Traffic Dialer filter triggers call if traffic is interesting Use sh ISDN history, debug dialer, and the ISDN mib to debug issues int bri 0 dialer-group 1 access-list 101 deny igrp 0.0.0.0 255.255.255.255 0.0.0.0 255.255.255.255 access-list 101 permit ip 0.0.0.0 255.255.255.255 0.0.0.0 255.255.255.255 dialer-list 1 list 101

Show ISDN History Router#sh isdn hist ------------------------------------------------------------- ISDN CALL HISTORY History Table MaxLength = 100 entries History Retain Timer = 15 Minutes ------------------------------------------------------------------------- Call Calling Called Duration Remote Time until Type Number Number Seconds Name Disconnect Out 01234 220 Paris Out 04567 521 LA Out 345 Failed In 43078 320 Orlando In 785601 Active(57) Brussels

Debug Dialer router# debug dialer events router# debug dialer packets Dialing cause: BRI0: ip (s=172.16.1.111 d=172.16.2.22) router# debug dialer packets BRI0: ip (s=10.1.1.8, d=10.1.1.1), 100 bytes, interesting (ip PERMIT)

Troubleshooting ISDN Be systematic Go step by step Ping remote int Debug dialer Sh isdn stat Layer 1 Layer 2 Layer 3 Debug PPP LCP Speed 56/64 Pap/chap NCP Ping remote net Tune cost Be systematic Go step by step Always troubleshoot both ends of the connection

1174_04F8_c1 88