Cisco 3900 Router randomly losing connection to the internet

[maisiba]

Cisco 3900 Router randomly losing connection to the internet, comes back when I bounce the WAN port. Any idea how I may pin the cause of problem?

Issue is not with ISP as a direct ISP to PC connection is stable and never disconnects.

[balaji.bandi]

Cisco 3900 Router randomly losing connection to the internet 

what kind of internet speed ? what is the Logs show when you lost internet ? from router are you able to ping ISP ip address ?

what is the IOS running, and post the config here ? (if possible)

show run

show version

show interface gi x/x

[maisiba]

Connected to a 35Mbps BW.

When internet connection is lost, WAN interface is up, I can't ping ISP default gateway. 

I issue shut and no shut on WAN interface, internet is restored

Router#sh ver
Cisco IOS Software, C3900 Software (C3900-UNIVERSALK9-M), Version 15.1(4)M5, REL EASE SOFTWARE (fc1)
Technical Support: http://www.cisco.com/techsupport
Copyright (c) 1986-2012 by Cisco Systems, Inc.
Compiled Tue 04-Sep-12 18:30 by prod_rel_team

ROM: System Bootstrap, Version 15.0(1r)M16, RELEASE SOFTWARE (fc1)

Router uptime is 25 minutes
System returned to ROM by power-on
System restarted at 12:05:18 UTC Thu Nov 18 2021
System image file is "flash0:c3900-universalk9-mz.SPA.151-4.M5.bin"
Last reload type: Normal Reload


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Cisco CISCO3925-CHASSIS (revision 1.0) with C3900-SPE100/K9 with 995328K/53248K bytes of memory.
Processor board ID FCZ1xxx7UH3
3 Gigabit Ethernet interfaces
1 terminal line
1 Channelized (E1 or T1)/PRI port
1 Virtual Private Network (VPN) Module
DRAM configuration is 72 bits wide with parity enabled.
255K bytes of non-volatile configuration memory.
250880K bytes of ATA System CompactFlash 0 (Read/Write)


License Info:

License UDI:

-------------------------------------------------
Device# PID SN
-------------------------------------------------
*0 C3900-SPE100/K9 FOC164771Q6




Technology Package License Information for Module:'c3900'

-----------------------------------------------------------------
Technology Technology-package Technology-package
Current Type Next reboot
------------------------------------------------------------------
ipbase ipbasek9 Permanent ipbasek9
security securityk9 Permanent securityk9
uc uck9 Permanent uck9
data None None None

Configuration register is 0x2102




Router# sh ip int b
Interface IP-Address OK? Method Status Protocol
Embedded-Service-Engine0/0 unassigned YES NVRAM initializing down
GigabitEthernet0/0 unassigned YES NVRAM up up
GigabitEthernet0/0.2432 158.xx.30 YES NVRAM administratively down down
GigabitEthernet0/0.2641 62.xx.207 YES NVRAM up up
GigabitEthernet0/1 unassigned YES NVRAM up up
GigabitEthernet0/1.1 unassigned YES unset up up
GigabitEthernet0/1.200 172.30.235.1 YES NVRAM up up
GigabitEthernet0/2 154.xx.126 YES NVRAM up up
NVI0 62.xx.207 YES unset up up
Tunnel0 172.29.1.26 YES NVRAM up up




Router#sh int g0/2
GigabitEthernet0/2 is up, line protocol is up
Hardware is PQ3_TSEC, address is 4403.a707.b482 (bia 4403.a707.b482)
Description: xx
Internet address is 154.xx.126/31
MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,
reliability 253/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Half Duplex, 100Mbps, media type is RJ45
output flow-control is unsupported, input flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output 00:00:00, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 59094
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 62000 bits/sec, 11 packets/sec
5 minute output rate 48000 bits/sec, 25 packets/sec
93487 packets input, 97858292 bytes, 0 no buffer
Received 147 broadcasts (0 IP multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 0 multicast, 0 pause input
77273 packets output, 15287033 bytes, 0 underruns
3118 output errors, 8000 collisions, 124 interface resets
0 unknown protocol drops
0 babbles, 125 late collision, 2989 deferred
1 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out

The router configs are very okay, its been running well for years with no issues until last week when it started dropping internet connection.

[Georg Pauwen · Accepted solution]

Hello,

your problems are marked in bold. If reliability is not 255/255, there most likely is a hardware problem. Try and change the Ethernet cable first (use a Cat6 or Cat6a cable). Also, set the duplex mode to 'full':

interface GigabitEthernet0/2

--> duplex full




Router#sh int g0/2
GigabitEthernet0/2 is up, line protocol is up
Hardware is PQ3_TSEC, address is 4403.a707.b482 (bia 4403.a707.b482)
Description: xx
Internet address is 154.xx.126/31
MTU 1500 bytes, BW 100000 Kbit/sec, DLY 100 usec,
reliability 253/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Half Duplex, 100Mbps, media type is RJ45
output flow-control is unsupported, input flow-control is unsupported
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output 00:00:00, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 59094
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 62000 bits/sec, 11 packets/sec
5 minute output rate 48000 bits/sec, 25 packets/sec
93487 packets input, 97858292 bytes, 0 no buffer
Received 147 broadcasts (0 IP multicasts)
0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 0 multicast, 0 pause input
77273 packets output, 15287033 bytes, 0 underruns
3118 output errors, 8000 collisions, 124 interface resets
0 unknown protocol drops
0 babbles, 125 late collision, 2989 deferred
1 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out

[maisiba]

Executed --> duplex full 

on int G0/2 and kicked me out from remote access and can't ping it from public.

[Georg Pauwen]

Hello,

get with your ISP, they must set their end to full duplex as well. Nobody (and for a very long time) is using half duplex anymore.

[balaji.bandi]

You can not do this change from remote, this have many side effects, you like to do this change, you need to set router to reboot after certain time, so router can reboot and get in to old settings, in this sitation you need to reboot device since you have not saved config here.

For teting, if the ISP delivered Ethernet ( between ISP and Router put small switch and see if that resolve any issue ?)

ISP---Ethernet----Small Switch---Router 3900

[marce1000]

 - Adding to G. : changing this mode sometimes also requires a re-connecting or re-connection-action at the other side too , so that the duplex-protocol can , again. be agreed upon.

 M.

[Leo Laohoo]

---

@maisiba wrote:

reliability 253/255

---

I am with @Georg Pauwen here.  There are several thing wrong with this router's connection and router's port configuration. 
Firstly, there is a cable issue.  This is why the reliability is <255.  Both values must be 255, i. e.  255/255, and never lower than 255.

---

@maisiba wrote:

Half Duplex, 100Mbps, media type is RJ45

---

Next, what is the port configuration of the router?  Why is the link Half Duplex?  Is the speed and duplex settings hard-coded?

The output errors are attributed to the Half Duplex. 

The Total Output Drops are, probably, due to the cable issue where the router is sending packets repeatedly.

[marce1000]

 - Have a "syslog-server" in-da-house and make the device using it. Followup on logging , this may get further insights. It makes it easier too , to have an overview of logs during a longer time period.

 M.

[maisiba]

Considering for a sy-log server, hard to pin down the issue without logs

[Georg Pauwen]

Hello,

how old is the router ? The 3900 is end-of-sale as of 2017, so yours can be anywhere between 4 and x years old.

Who is your ISP ?

[maisiba]

Yeah, its an old router. Planning to replace.
Using a local ISP, Airtel, as indicated, ISP is not an issue here.