SNMP only works half the time.

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jbarbieri
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Joined: 06 Apr 2007
Posts: 545
Location: New Hampshire

PostPosted: Mon Sep 29, 2008 18:12    Post subject: SNMP only works half the time. Reply with quote
Hey there, I am trying to figure out why SNMP only works half the time.

Sometimes, it will run fine, even from the router itself (doing an snmpwalk -v 2c -c community localhost bla bla)

However, the other half of the time, I repeatadly get "request timed out"

Doing a TCPDUMP, I can see the request go into the socket:

15:11:03.289676 IP localhost.1024 > localhost.snmp: C=community GetNextRequest(25)


But it just hangs out.....and I can see the client retry a couple more times, then gives up.

The graph I attached also follows this trend.

Anyone else having SNMP issues?



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cpu-graph.png



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Netgear WNR2000v3 | 2nd Floor AP | DD-WRT v3.0-r27805 std

Behind a Raspberry Pi Dual WAN router
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soulstace
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Joined: 04 Aug 2007
Posts: 6427

PostPosted: Mon Sep 29, 2008 19:04    Post subject: Reply with quote
Anything to do with this?

http://svn.dd-wrt.com:8000/dd-wrt/changeset/10429
jbarbieri
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Joined: 06 Apr 2007
Posts: 545
Location: New Hampshire

PostPosted: Tue Sep 30, 2008 12:36    Post subject: Reply with quote
Hmm, I dunno, is that them fixing SNMP or breaking it.

I am running:

DD-WRT v24-sp2 (09/26/08) std - build 10431M NEWD Eko

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Linksys EA6500v2 | 5GHz 1st Floor AP | Advanced Tomato 1.28.0000 -2.9-131 K26ARM USB AIO-64K
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Behind a Raspberry Pi Dual WAN router
switch
DD-WRT Guru


Joined: 30 Apr 2008
Posts: 967
Location: Romania

PostPosted: Tue Sep 30, 2008 13:01    Post subject: Reply with quote
There's a possible cause for your problem: the CPU is overloaded most of the time! Not sure about that though, since my own Asus registers just fine at loads of over 2.5 with MRTG running on the same platform; still, I'm using an older version so maybe that's it.
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jbarbieri
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Joined: 06 Apr 2007
Posts: 545
Location: New Hampshire

PostPosted: Tue Sep 30, 2008 13:09    Post subject: Reply with quote
No, my CPU isnt always overloaded, look @ my sig.

It just so happens, when my CPU is overloaded, it decides that SNMP will work.

Right now I am at:

Code:

Mem: 17716K used, 11540K free, 0K shrd, 1596K buff, 6364K cached
CPU:  9.8% usr  5.1% sys  0.0% nice 85.0% idle  0.0% io  0.0% irq  0.0% softirq
Load average: 0.01 0.08 0.08

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Linksys EA6500v2 | 5GHz 1st Floor AP | Advanced Tomato 1.28.0000 -2.9-131 K26ARM USB AIO-64K
Netgear WNR2000v3 | 2nd Floor AP | DD-WRT v3.0-r27805 std

Behind a Raspberry Pi Dual WAN router
switch
DD-WRT Guru


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Posts: 967
Location: Romania

PostPosted: Tue Sep 30, 2008 13:12    Post subject: Reply with quote
Wait, so during >1 loads, SNMP works, otherwise it doesn't?
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jbarbieri
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Joined: 06 Apr 2007
Posts: 545
Location: New Hampshire

PostPosted: Tue Sep 30, 2008 13:37    Post subject: Reply with quote
Lets test, my CPU should start to climb, I will see if it starts reporting right.
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Linksys EA6500v2 | 5GHz 1st Floor AP | Advanced Tomato 1.28.0000 -2.9-131 K26ARM USB AIO-64K
Netgear WNR2000v3 | 2nd Floor AP | DD-WRT v3.0-r27805 std

Behind a Raspberry Pi Dual WAN router
jbarbieri
DD-WRT Guru


Joined: 06 Apr 2007
Posts: 545
Location: New Hampshire

PostPosted: Tue Sep 30, 2008 14:09    Post subject: Reply with quote
haha yep

My graphs are working again,


Code:
Mem: 17892K used, 11364K free, 0K shrd, 1612K buff, 6548K cached
CPU:  3.8% usr 91.8% sys  0.0% nice  4.3% idle  0.0% io  0.0% irq  0.0% softirq
Load average: 2.20 1.65 1.04


Different scales, but you can see they started working at the same time again.



mem.png
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mem.png



cpu.png
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cpu.png



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Linksys EA6500v2 | 5GHz 1st Floor AP | Advanced Tomato 1.28.0000 -2.9-131 K26ARM USB AIO-64K
Netgear WNR2000v3 | 2nd Floor AP | DD-WRT v3.0-r27805 std

Behind a Raspberry Pi Dual WAN router
switch
DD-WRT Guru


Joined: 30 Apr 2008
Posts: 967
Location: Romania

PostPosted: Tue Sep 30, 2008 16:42    Post subject: Reply with quote
This is simply weird. Got any leads on it?
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jbarbieri
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Joined: 06 Apr 2007
Posts: 545
Location: New Hampshire

PostPosted: Thu Jan 22, 2009 17:55    Post subject: Reply with quote
I am still having this problem.


DD-WRT v24-sp2 (01/10/09) std-nokaid
(SVN revision 11361)

Thats the version I am currently running.



cpu.png
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cpu.png



mem.png
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mem.png



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Linksys EA6500v2 | 5GHz 1st Floor AP | Advanced Tomato 1.28.0000 -2.9-131 K26ARM USB AIO-64K
Netgear WNR2000v3 | 2nd Floor AP | DD-WRT v3.0-r27805 std

Behind a Raspberry Pi Dual WAN router
frater
DD-WRT Guru


Joined: 07 Jun 2006
Posts: 2777

PostPosted: Thu Jan 22, 2009 18:10    Post subject: Reply with quote
Do you have a Linux-system that will run this 1-minute cronjob?

Code:
#!/bin/sh
echo "`date` `nmap -sU -p 161 -T Aggressive 192.168.1.1 | grep open`" >>/var/log/snmp-log

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Asus RT16N + OTRW
Kingston 4GB USB-disk 128 MB swap + 1.4GB ext3 on /opt + 2 GB ext3 on /mnt
Copperjet 1616 modem in ZipB-config
Asterisk, pixelserv & Pound running on router
Another Asus RT16N as WDS-bridge

DD-WRT v24-sp2 vpn (c) 2010 NewMedia-NET GmbH
Release: 12/16/10 (SVN revision: 15758M)
jbarbieri
DD-WRT Guru


Joined: 06 Apr 2007
Posts: 545
Location: New Hampshire

PostPosted: Thu Jan 22, 2009 18:12    Post subject: Reply with quote
frater wrote:
Do you have a Linux-system that will run this 1-minute cronjob?

Code:
#!/bin/sh
echo "`date` `nmap -sU -p 161 -T Aggressive 192.168.1.1 | grep open`" >>/var/log/snmp-log



No, not on the LAN.

I am monitoring it from the Internet though.

So far, nmap says its been open.

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Linksys EA6500v2 | 5GHz 1st Floor AP | Advanced Tomato 1.28.0000 -2.9-131 K26ARM USB AIO-64K
Netgear WNR2000v3 | 2nd Floor AP | DD-WRT v3.0-r27805 std

Behind a Raspberry Pi Dual WAN router


Last edited by jbarbieri on Thu Jan 22, 2009 18:20; edited 1 time in total
jbarbieri
DD-WRT Guru


Joined: 06 Apr 2007
Posts: 545
Location: New Hampshire

PostPosted: Thu Jan 22, 2009 18:22    Post subject: Reply with quote
Code:
Thu Jan 22 12:13:01 EST 2009 161/udp open|filtered snmp
Thu Jan 22 12:14:01 EST 2009 161/udp open|filtered snmp
Thu Jan 22 12:15:01 EST 2009 161/udp open|filtered snmp
Thu Jan 22 12:16:01 EST 2009 161/udp open|filtered snmp

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Netgear WNR2000v3 | 2nd Floor AP | DD-WRT v3.0-r27805 std

Behind a Raspberry Pi Dual WAN router
Setarcos
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Joined: 11 Nov 2008
Posts: 6
Location: San Jose, CA

PostPosted: Thu Jan 22, 2009 21:27    Post subject: Reply with quote
I know it's old, but it works fine for me on v24-sp1.

The dd-wrt specific stuff below .1.3.6.1.4.1.2021.255.3.54.1.3.32.1 seems to have some issues though (must be something to do with how the pass_persist shell script is working)



setswap-CPU.png
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Cacti CPU usage graph
 Filesize:  42.85 KB
 Viewed:  13152 Time(s)

setswap-CPU.png


jbarbieri
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Joined: 06 Apr 2007
Posts: 545
Location: New Hampshire

PostPosted: Fri Jan 23, 2009 0:54    Post subject: Reply with quote
Setarcos wrote:
I know it's old, but it works fine for me on v24-sp1.

The dd-wrt specific stuff below .1.3.6.1.4.1.2021.255.3.54.1.3.32.1 seems to have some issues though (must be something to do with how the pass_persist shell script is working)



yea, it sometimes it seems like, when it gets into the wl_snmpd.sh stuff, it breaks.


:( I wish it would work, I'd love to just monitor the damn thing.

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Linksys EA6500v2 | 5GHz 1st Floor AP | Advanced Tomato 1.28.0000 -2.9-131 K26ARM USB AIO-64K
Netgear WNR2000v3 | 2nd Floor AP | DD-WRT v3.0-r27805 std

Behind a Raspberry Pi Dual WAN router
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