Intermittent internet issue

[Randyx]

Hi,

We have been experiencing random intermittent internet connection. What I noticed though is whenever we are experiencing slow internet connection, our access to our Internet Router is also not stable.

Ping from Internet router to outside address, the latency is normal and no packet drops.

Ping from any PC to outside address, very slow and lots of packet drops. I also noticed that when the issue with internet connection occurs, access to the Internet router is sluggish.

I did a continuous ping to outside address and the Internet router at the same time, the packet loss seems to occur at the same time.

I checked switches, routers and firewalls interfaces but did not find anything that has an high number of errors or output drops or even duplex mismatch.

Any suggestions?

Thanks in advance

[mvsheik123]

Hi,

Based on details in the post, it looks like internal issue. How is your network setup (basic diagram/configs). Issue related all users or specific subnet traffic? Share some details.

Thx

MS

[Reza Sharifi]

Hi,

If from the Internet router pings are normal and there is no packet loss than there is no issue with the provider or Internet connection. The problem seems to be internal to your network.  Can you check firewalls and other devices on the patch for high CPU? Also, do you have ACL on the Internet router and the firewalls blocking unwanted traffic from the Internet?  

HTH

[Randyx]

During that time, the CPU utilization was normal for all of the devices. No access-list on the router for blocking traffic from the Internet. We have traffic shaping in place which I suppose is not the cause of the issue.

Other thing I noticed was when I ping all other device on the network leading up to the Internet router,there was no latency and packet drops. But ping to Internet router was very slow.

Here is the basic logical diagram.

Access_LayerSW-->CoreSW-->FW-->BPZSW--IntFW-->IntRTR

Physically, the IntFW and IntRTR are both connected to BPZSW on the same VLAN.

[Georg Pauwen]

Hello,

what platform is your router (e.g. ISR4331) ? There are so many devices in front of your router that it is impossible to tell which one is the culprit. I would connect a PC directly to the router and test the connection, than connect the PC to the next downstream device, and so on, until you find the one that causes the delay...

[Randyx]

Hi Georg,

Thanks for the response, please see information below.

Cisco 2851 (revision 53.51)
Cisco IOS Software, 2800 Software (C2800NM-ADVIPSERVICESK9-M), Version 12.4(22)T5

Thanks,

Randy

[Georg Pauwen]

Hello,

the 2851's end of life/end of sale date is somewhere around 2011. I am not saying that this IS the problem, but with hardware that old, this could be an issue. What kind of Internet connection do you have, what is the up/down speed ?

[Randyx]

Hi Georg,

We have a dedicated Internet with 24mbp speed which is burstible to 60mbps.

In addition, we've been seeing this logs on the router, not sure if this could be related.

%ENVMON-4-FAN_LOW_RPM: Fan 1 service recommended

Thanks

[Georg Pauwen · Accepted solution]

Hello,

if you feel comfortable enough to do this, open the chassis and reseat the fan tray. Also check if there is dust or dirt on the fan.

I don't really think that this is related to your intermittent failures, but it could be indicative of...old hardware that is about to die. How long is this router in service ?

[Randyx]

Hi Georg,

The office has been setup fairly recently. The router has been up for over a year.

What else can you suggest I should check?

Thanks

[Georg Pauwen · Accepted solution]

Hello,

the first thing I would do is reboot the router, an uptime of > 1 year by itself is quite long. See if you can get the fan issue resolved, and connect a PC directly to the router. When the other users experience problems, check if the PC directly connected to the router has the same problem. If not, you know the router is not the problem...

[Randyx]

Hi Georg,

I kind of did similar to this. When issue is happening, I logged to both BPZSW and IntFW devices. I did ping from both devices to the IntRTR and they are experiencing packet drops.

I try your suggestion next time it happens.

Thanks for helping out..More power to you!!