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WAN monitoring RT-N66U (snmpd)

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radek.pribyl

New Around Here
Hi all,

I'm running RT-N66U with forked Merlin's firmware (374.43 (V15E5)). I've had some issues with WAN performance (ISP issue) and decided to start monitoring WAN traffic to have some measurements. For that I installed:
- snmpd (5.4.4-2) using Entware
- rrdtool (1.2.30-3a) using Entware

I configured the snmp agent and created a cron job to collect the
ifInOctets and IfOutOctets on eth0 (2) interface every 5 minutes using snmpget. From what I understand eth0 should be the WAN interface. However when I generated the graphs and looked at the data I discovered these strange behaviors:

1. I have HDD connected to the router for backup and acting as media server. When I looked at the data (and confirmed by tests) I discovered that any data transfer from local computer to the attached disk is reported as incoming / outgoing traffic on eth0. This impacts the data as the speed of LAN is significantly higher

2. When some data is downloaded from internet the amount of incoming and outgoing data on eth0 is almost identical. In connection with #1 it looks to me like the counters are increased firstly for incoming traffic between internet and WAN interface and secondly as outgoing traffic between WAN interface and the local computer.

Initially I thought the issue was in the way I collected and displayed the data using rrdtool. So I started logging the data from snmpget calls and the results looked like:

ifInOctets
.1.3.6.1.2.1.2.2.1.10.2
Initial counter's value: 17287658
After 5 mins: 162231124 delta vs. previous: 144943466
After 5 mins: 345631192 delta vs. previous: 183400068

and
IfOutOctets
.1.3.6.1.2.1.2.2.1.16.2
Initial counter's value: 2391394570
After 5 mins: 2535717414 delta vs. previous: 144322844
After 5 mins: 2718071239 delta vs. previous: 182353825

This was for a period when I downloaded data from internet without any other activities. You can see the deltas for both counters are very similar.

As I'm running out of ideas - does anybody have any idea why the counters on eth0 count also traffic between the router and end computer?

P.S. The Traffic Monitor shows the traffic for Internet properly when looking at Internet tab. Not sure if the source of data is different
Thanks a lot for any suggestion.
Radek
 
Last edited:
One findings - the issues seems to be related to clients connected over wired connection. For wireless connections the outgoing traffic is not generated on eth0 which is correct. Still no idea why the numbers are screwed for wired connections ...
 

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