Carrier Transitions/Loss of Frame Between Cisco 1720 Routers !

[evilh]

We have a Point-to-Point Fractional T1 connection between two of our offices. There is a Cisco 1720 on each end. Without any config changes, the connectivity between the offices has started behaving very unusual. Line is up, protocol is up. I can ping servers on both sides of the routers. However, people at the remote location cannot see anything on our section of the domain in Network Neighborhood, we can see them. But if they do a Start-Find-Computer it will find the machine in question. They can open shares on servers located on our side. However, their Outlook clients cannot find the Exchange Server. They can Ping the exchange server from their location. Internet Explorer is also not finding our proxy server - which they can also Ping.

Both interfaces on the routers in question are showing that the line is up, the protocol is up, the circuit is up. However, they are both getting Carrier Transition errors, Loss of Frame errors, input errors, and interface resets.

I have checked: encapsulation, framing, clocking, the circuit. Is it possible that I have a bad CSU/DSU in one of the routers and if yes, how do I tell which router has the faulty module?

Any ideas or suggestions would be appreciated.

Please forgive my astounding ignorance.

 

[mildmanrd]

Hi evilh,

I would try placing a loopback plug in the wic card and issue the debug serial interface command. If the keepalives are incrementing then your card is fine, if they don't then it may be faulty. Also on your remote router I would verify that you are using the ip helper-address command to forward netbios info.

good luck

 

[jeter]

do a show service-module and look at the errors.

Has the span been tested by your local telephone
company?

mldmanrd has a good idea about looping up the csu/dsu.

Can you post a ( show interface 0 ) I want to check out the parameters. Jeter@LasVegas.com
J.Fisher CCNA

 

[evilh]

>jeter (TechnicalUser) Jul 13, 2001 asked:
do a show service-module and look at the errors.

I did - that is where I see the carrier transitions and loss of frame.

> Has the span been tested by your local telephone
company?

Yes, they say the circuit is fine.


> Can you post a ( show interface 0 ) I want to check out the parameters.

This is the interface on the remote router:

Serial0 is up, line protocol is up
Hardware is PQUICC with Fractional T1 CSU/DSU
Description: connected to dcisco
Interface is unnumbered. Using address of FastEthernet0 (192.168.101.3)
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation PPP, loopback not set
Keepalive set (10 sec)
LCP Open
Open: IPCP, CDPCP
Last input 00:00:00, output 00:00:00, output hang never
Last clearing of "show interface" counters 2d16h
Input queue: 0/75/0 (size/max/drops); Total output drops: 0
Queueing strategy: weighted fair
Output queue: 0/1000/64/0 (size/max total/threshold/drops)
Conversations 0/2/256 (active/max active/max total)
Reserved Conversations 0/0 (allocated/max allocated)
5 minute input rate 0 bits/sec, 2 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
61435 packets input, 5206840 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
61405 packets output, 2600815 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 output buffer failures, 0 output buffers swapped out
1 carrier transitions
DCD=up DSR=up DTR=up RTS=up CTS=up

This is the interface on the main router:
Serial1 is up, line protocol is up
Hardware is PQUICC with Fractional T1 CSU/DSU
Description: connected to Composites
Interface is unnumbered. Using address of FastEthernet0 (192.168.100.3)
MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation PPP, loopback not set
Keepalive set (10 sec)
LCP Open
Open: IPCP, CDPCP
Last input 00:00:01, output 00:00:01, output hang never
Last clearing of "show interface" counters 4d16h
Input queue: 0/75/0 (size/max/drops); Total output drops: 0
Queueing strategy: weighted fair
Output queue: 0/1000/64/0 (size/max total/threshold/drops)
Conversations 0/2/256 (active/max active/max total)
Reserved Conversations 0/0 (allocated/max allocated)
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 0 packets/sec
116980 packets input, 5392567 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 1 giants, 0 throttles
3 input errors, 0 CRC, 2 frame, 0 overrun, 0 ignored, 1 abort
117561 packets output, 10069463 bytes, 0 underruns
0 output errors, 0 collisions, 5 interface resets
0 output buffer failures, 0 output buffers swapped out
4 carrier transitions
DCD=up DSR=up DTR=up RTS=up CTS=up

I try the loopback and let you know. Meanwhile, any other ideas would be appreciated.

 

[evilh]

Information update. The remote site's outlook clients can intermittently connect to the Exchange server. It's like the connection is fuzzy and then clear for a few seconds, then fuzzy again. This intermittent connectivity happens without any changes being made to the server, workstations, or routers.

 

[McMike]

Tried the old substitution method? Intermittant error is so difficult to catch even with software traps because they must capture the error instant, not just the time interval stats (though the stats may indicate trouble).

Dispite the hassle, perhaps using another router, with the same config, will show something. Both ends at the same time would be even better.

Tip #2: span testing is half determination by the telco testers. My experience is that telcos may not find a problem until you point it out to them. I have heard of local people who have closed their business because PacBell could not provide them with good copper.

Best
MikeM

 

[wybnormal]

If you look at the stats, the remote router shows clean.. but the main router is showing interface resets.. normally this occurs when the router *loses* the keep alives coming from the CO for some reason. Overloading, bad line, bad line card at the CO etc. You have to hammer the Telco for better testing then just dropping in a seeing if there is data. I have 2 circuits down.. the same way.. took ten hours to convince the Telco the problem was one their side..even after we figured out they both fed off the same switch at the CO... bad card in the end.

MikeS
"Diplomacy; the art of saying 'nice doggie' till you can find a rock" Wynn Catlin

 

[jeter]

Is the server at 1 end of the PPP?
Did you setup a ip helper address?
The reason I ask is I ran into this
problem a few weeks ago and it appears
to have the same trouble. Jeter@LasVegas.com
J.Fisher CCNA