03-30-2012 11:35 PM - edited 03-04-2019 03:52 PM
Hi,
In one of my client location cisco 1841 router and the link is down.
while i troubleshooting the serial interface they show like this.
so i check with the service provider they told line is ok.
how to i locate the problem.
how to troubleshoot??/where is the problem our end or service provider end???
Serial0/1/0 is up, line protocol is down
Hardware is GT96K Serial
Internet address is 192.168.109.53/30
MTU 1500 bytes, BW 1544 Kbit/sec, DLY 20000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation PPP, LCP ACKsent, loopback not set
Keepalive set (10 sec)
Last input 00:00:00, output 00:00:00, output hang never
Last clearing of "show interface" counters 02:47:29
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: weighted fair
Output queue: 0/1000/64/0 (size/max total/threshold/drops)
Conversations 0/1/256 (active/max active/max total)
Reserved Conversations 0/0 (allocated/max allocated)
Available Bandwidth 1158 kilobits/sec
5 minute input rate 0 bits/sec, 0 packets/sec
5 minute output rate 0 bits/sec, 1 packets/sec
299 packets input, 4186 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 3 giants, 0 throttles
424 input errors, 424 CRC, 213 frame, 4 overrun, 0 ignored, 212 abort
874 packets output, 12236 bytes, 0 underruns
0 output errors, 0 collisions, 53 interface resets
0 unknown protocol drops
0 output buffer failures, 0 output buffers swapped out
13 carrier transitions
DCD=up DSR=up DTR=up RTS=up CTS=up
03-31-2012 12:02 AM
Hi,
It seems that you have errors and CRC to your interface
424 input errors, 424 CRC, 213 frame, 4 overrun, 0 ignored, 212 abort
Be sure that the link is ok.
you should have a layer 2 problem.
Serial0/1/0 is up, line protocol is down
Check the mtu and full duplex is the same to both interface ends.
Also check any L2 encapsulation config. PPP config should be the correct and similar to both ends
Hope that helps
Vasilis
03-31-2012 12:52 AM
I clear the error and CRC using the command clear counter.
Config:
RDC-GODOWN#sh running-config
Building configuration...
Current configuration : 2260 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname RDC-GODOWN
!
boot-start-marker
boot-end-marker
!
logging buffered 51200 notifications
enable secret 5 $1$DGSg$2d/PkBqOj7iypcHH6S8v80
enable password cisco
!
no aaa new-model
ip cef
!
!
!
!
multilink bundle-name authenticated
isdn switch-type basic-net3
!
!
username cisco privilege 15 secret 5 $1$qB55$CoVxYzC/y/oB3SCOv0qw90
archive
log config
hidekeys
!
!
!
!
!
interface FastEthernet0/0
ip address 10.20.245.100 255.255.255.0
duplex auto
speed auto
keepalive 1000
!
interface FastEthernet0/1
no ip address
duplex auto
speed auto
!
interface BRI0/0/0
ip address negotiated
encapsulation ppp
dialer idle-timeout 180
dialer string 04428299970
dialer load-threshold 200 either
dialer watch-disable 15
dialer watch-group 10
dialer-group 1
isdn switch-type basic-net3
isdn point-to-point-setup
ppp authentication chap
ppp multilink
!
interface Serial0/1/0
bandwidth 128
ip address 192.168.109.53 255.255.255.252
ip accounting output-packets
encapsulation ppp
!
router eigrp 100
passive-interface default
no passive-interface BRI0/0/0
network 10.0.0.0
no auto-summary
!
router bgp 65001
no synchronization
bgp log-neighbor-changes
network 10.10.245.0 mask 255.255.255.0
neighbor 192.168.109.54 remote-as 9829
no auto-summary
!
ip forward-protocol nd
!
!
no ip http server
!
snmp-server community startrac RW 55
snmp-server ifindex persist
snmp-server location ***DELHI-RO***
snmp-server contact ***Datacraft GSC , Bangalore***
snmp-server enable traps snmp authentication linkdown linkup coldstart warmstart
snmp-server enable traps envmon
snmp-server enable traps config
snmp-server enable traps cpu threshold
snmp-server host 152.102.153.235 startrac
Can u check any problem in my config.
How to check mtu value??
Any problem in modem or cable???
03-31-2012 02:17 AM
hi,
ask the SP to give you a loopback from the nearest exchange towards the 1841. you must check from inside LAN and should see the serial link to be up/up (looped). if it's still up/down, push the SP to dispatch an onsite technician to check the cabling or the NTU.
03-31-2012 03:14 AM
I am not getting loop from my nearest exchange.
Any problem in modem or sp cable pair??
03-31-2012 03:26 AM
yes and it's highly probable. ask the SP to send a tech in order to rectify your issue.
03-31-2012 03:46 AM
Thanks for ur information...
03-31-2012 04:56 AM
Hi,
I do not see any problem to your config.
Your mtu value can be checked with the show interface command.
To the provided output is 1500bytes
Serial0/1/0 is up, line protocol is down
Hardware is GT96K Serial
Internet address is 192.168.109.53/30
MTU 1500 bytes, BW 1544 Kbit/sec, DLY 20000 usec,
Encapsulation PPP
It should be the same to the other endpoint.
The ppp negotiation is stuck to the LCP phase
(from your output)
Serial0/1/0 is up, line protocol is down
Hardware is GT96K Serial
Internet address is 192.168.109.53/30
MTU 1500 bytes, BW 1544 Kbit/sec, DLY 20000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation PPP, LCP ACKsent, loopback not set
If you type debug ppp negotiation you will see that L2 fails (ppp to be established) and this is the reason that the interface is up/down
Regards,
Vasilis
04-01-2012 10:17 PM
I given the command debug ppp negotiation in the router
it shows like
PPP protocol negotiation debugging is on.
No error has came.
After that what i am to check?
04-02-2012 12:02 AM
PPP can not be established otherwise you should see this subent as connected to the show ip route output.
Can you see this subnet to the routing table?
It seems that should be an error in the physical layer. I would suggest to procced with the actions mentioned by johnlloyd13
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