Cisco 877W Router - DSL connectivity issue

Alex Fray · ‎06-10-2011

I'm using a Cisco 877W router which connects to a private broadband network using PPPoA. I have installed many other 800 series routers on broadband lines successfully so am familiar with DSL but cannot resolve this issue.

When i connect my router to the line i get a solid Carrier detect light and when doing a debug atm events i get "showtime" so all good. However when i debug ppp negotiation i am not able to authenticate. It is not that my CHAP/PAP username and password is wrong its that i don't even get to that point.

The router continually does a confreq over 30 times which times out which would indicate no response from the ISP:

000040: *May 4 11:54:51.157 BST: Vi2 LCP: O CONFREQ [REQsent] id 44 len 10

000041: *May 4 11:54:51.157 BST: Vi2 LCP: MagicNumber 0x75D5C4D8 (0x050675D5C4D8)

000042: *May 4 11:54:53.173 BST: Vi2 LCP: Timeout: State REQsent

However after 30+ time i eventually get a response (4 minutes later):

000179: *May 4 11:58:11.864 BST: Vi2 LCP: O CONFREQ [ACKsent] id 84 len 10

000180: *May 4 11:58:11.864 BST: Vi2 LCP: MagicNumber 0x75D8D4DD (0x050675D8D4DD)

000181: *May 4 11:58:11.896 BST: Vi2 LCP: I CONFACK [ACKsent] id 84 len 10

000182: *May 4 11:58:11.896 BST: Vi2 LCP: MagicNumber 0x75D8D4DD (0x050675D8D4DD)

000183: *May 4 11:58:11.896 BST: Vi2 LCP: State is Open

000184: *May 4 11:58:11.896 BST: Vi2 PPP: Phase is AUTHENTICATING, by the peer

000185: *May 4 11:58:11.896 BST: Vi2 CHAP: I CHALLENGE id 57 len 38 from "ERX15.Birmingham3"

000186: *May 4 11:58:15.960 BST: Vi2 CHAP: I CHALLENGE id 58 len 38 from "ERX15.Birmingham3"

000187: *May 4 11:58:20.061 BST: Vi2 CHAP: I CHALLENGE id 59 len 38 from "ERX15.Birmingham3"

000188: *May 4 11:58:21.913 BST: Vi2 AUTH: Timeout 1

000189: *May 4 11:58:24.161 BST: Vi2 CHAP: I CHALLENGE id 60 len 38 from "ERX15.Birmingham3"

000190: *May 4 11:58:28.262 BST: Vi2 CHAP: I CHALLENGE id 61 len 38 from "ERX15.Birmingham3"

000191: *May 4 11:58:31.926 BST: Vi2 AUTH: Timeout 2

000192: *May 4 11:58:32.358 BST: Vi2 CHAP: I CHALLENGE id 62 len 38 from "ERX15.Birmingham3"

000193: *May 4 11:58:36.459 BST: Vi2 CHAP: I CHALLENGE id 63 len 38 from "ERX15.Birmingham3"

000194: *May 4 11:58:40.559 BST: Vi2 CHAP: I CHALLENGE id 64 len 38 from "ERX15.Birmingham3"

000195: *May 4 11:58:41.944 BST: Vi2 AUTH: Timeout 3

000196: *May 4 11:58:44.660 BST: Vi2 CHAP: I CHALLENGE id 65 len 38 from "ERX15.Birmingham3"

000197: *May 4 11:58:48.773 BST: Vi2 CHAP: I CHALLENGE id 66 len 38 from "ERX15.Birmingham3"

000198: *May 4 11:58:51.961 BST: Vi2 AUTH: Timeout 4

000199: *May 4 11:58:52.869 BST: Vi2 CHAP: I CHALLENGE id 67 len 38 from "ERX15.Birmingham3"

000200: *May 4 11:58:56.966 BST: Vi2 LCP: I TERMREQ [Open] id 120 len 4

000201: *May 4 11:58:56.966 BST: Vi2 LCP: O TERMACK [Open] id 120 len 4

000202: *May 4 11:58:56.966 BST: Vi2 PPP: Sending Acct Event[Down] id[4]

000203: *May 4 11:58:56.970 BST: Vi2 PPP: Phase is TERMINATING

000204: *May 4 11:58:58.970 BST: Vi2 LCP: Timeout: State TERMsent

000205: *May 4 11:58:58.970 BST: Vi2 LCP: State is Closed

000206: *May 4 11:58:58.970 BST: Vi2 PPP: Phase is DOWN

Now to me this indicates an inbound packet from the ISP but now my router doesn't respond.

Is this a configuration issue with my router or an ISP problem. I have read the Cisco DSL Troubleshooting for PPPoA document but it doesn't cover this. my configuration is below:

interface ATM0

no ip address

no ip mroute-cache

no shut

atm vc-per-vp 64

no atm ilmi-keepalive

pvc 0/38

encapsulation aal5mux ppp dialer

dialer pool-member 1

interface Dialer1

ip address 10.x.x.1 255.255.255.254

ip inspect myfw out

ip virtual-reassembly

encapsulation ppp

dialer pool 1

dialer-group 1

ppp authentication chap pap callin

ppp chap hostname xxxx

ppp chap password yyyy

ppp pap sent-username xxxx password yyyy

ppp ipcp dns request

ppp ipcp wins request

hold-queue 224 in

thanks Alex

paolo bevilacqua · ‎06-10-2011

Which IOS are you using ?

Can you send "show dsl itnterface", "show int atm0". To rule out layer 1 issues.

Alex Fray · ‎06-13-2011

I had the PSTN provider come out to check the line and they confirmed it was ok. The fact i get a carrier detect should mean the line is ok. I'm just a bit confused that i do occassionally see some traffic from the ISP but don't complete the PPP negotiation.

IOS - c870-advsecurityk9-mz.124-24.T4.bin

sh int atm0 -

ATM0 is up, line protocol is up

Hardware is MPC ATMSAR (with Alcatel ADSL Module)

MTU 4470 bytes, sub MTU 4470, BW 448 Kbit/sec, DLY 820 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ATM, loopback not set

Encapsulation(s): AAL5 AAL2, PVC mode

10 maximum active VCs, 64 VCs per VP, 1 current VCCs

VC Auto Creation Disabled.

VC idle disconnect time: 300 seconds

Last input never, output 00:00:01, output hang never

Last clearing of "show interface" counters 00:02:58

Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: Per VC Queueing

5 minute input rate 0 bits/sec, 0 packets/sec

5 minute output rate 0 bits/sec, 0 packets/sec

15 packets input, 485 bytes, 0 no buffer

Received 0 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort

33 packets output, 525 bytes, 0 underruns

0 output errors, 0 collisions, 0 interface resets

0 unknown protocol drops

0 output buffer failures, 0 output buffers swapped out

sh dsl interface -

ATM0

Alcatel 20190 chipset information

ATU-R (DS) ATU-C (US)

Modem Status: Showtime (DMTDSL_SHOWTIME)

DSL Mode: ITU G.992.1 (G.DMT) Annex A

ITU STD NUM: 0x03 0x1

Vendor ID: 'STMI' 'ALCB'

Vendor Specific: 0x0000 0x0000

Vendor Country: 0x0F 0x0F

Chip ID: C196P (1) DFE BOM: DFE3.0 Annex A (1)

Capacity Used: 100% 59%

Noise Margin: 8.0 dB 18.0 dB

Output Power: 15.5 dBm 12.0

dBm Attenuation: 52.0 dB 31.5 dB

FEC ES Errors: 0 0

ES Errors: 23 1

SES Errors: 0 0

LOSES Errors: 0 0

UES Errors: 0 0

Defect Status: None None Last Fail Code: None Watchdog Counter: 0xAB Watchdog Resets: 0 Selftest Result: 0x00 Subfunction: 0x00

Interrupts: 8252 (0 spurious)

PHY Access Err: 0

Activations: 1

LED Status: ON

LED On Time: 100

LED Off Time: 100

Init FW: init_AMR-3.0.014_no_bist.bin

Operation FW: AMR-3.0.014.bin

FW Source: embedded

FW Version: 3.0.14 Interleave Fast Interleave Fast

Speed (kbps): 1888 0 448 0

Cells: 13620 0 337927022 0

Reed-Solomon EC: 35751 0 0 0

CRC Errors: 25 0 6 0

Header Errors: 17 0 0 0

Total BER: 7419E-12 0E-0

Leakage Average BER: 9931E-12 0E-0

ATU-R (DS) ATU-C (US)

Bitswap: enabled enabled

Bitswap success: 0 0

Bitswap failure: 0 0

LOM Monitoring : Disabled

DMT Bits Per Bin 000: output omitted by alex fray

Training log buffer capability is not enabled

paolo bevilacqua · ‎06-13-2011

The circuit has very high attenuation and quite a few errors.

I think there is layer 1 problem here.

However the router also responds strangely to PPP, can you try a different IOS ?

Alex Fray · ‎06-13-2011

What is a good db range for attenuation?

i upgraded the IOS from T4 to T5 (c870-advsecurityk9-mz.124-24.T5.bin ) but still no joy, same result.

paolo bevilacqua · ‎06-13-2011

One random link, you can find more by searching.

http://www.naschenweng.info/2008/10/16/adsl-significance-of-snr-and-attenuation

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