1841 Router Low on memory; try again later

Unanswered Question
Aug 5th, 2010

Hello,

I do not know what is happening with my router, connects in a few days my users saying that the connection is not responding.
So I try to access remotely and does not respond to ping.
Interface console appears the message "Low on memory; try again later."
This is already the second router I'm using, I changed two days ago, and now caught again.
There is only a single wireless router connected to the network interface, which covers four users.

Attached with the settings and the screen with the problem.

I have this problem too.
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Leo Laohoo Thu, 08/05/2010 - 16:33

"Low on memory; try again later." is always a sign of an IOS bug.

Nagaraja Thanthry Thu, 08/05/2010 - 16:37

Hello,

Seems like your router is experiencing memory leak. Can you post the output

of "show process memory" output here? You might have to reboot the router to

login and then collect the output. You need to collect that output at

regular intervals for next couple of days for us to figure out which process

is leaking the memory.

Regards,

NT

Nagaraja Thanthry Thu, 08/05/2010 - 16:38

Hello,

Alternatively, you can also upgrade the code on the router to the latest

available. Make sure that you have enough memory (Flash/DRAM) to load the

new image.

Hope this helps.

Regards,

NT

glen.grant Fri, 08/06/2010 - 04:30

  Upgrade to a newer IOS version , it is usually a  memory leak as has been posted and the only fix is to reboot the router to free the memory .

Nagaraja Thanthry Fri, 08/06/2010 - 07:06

Hello,

What routing protocol you are running on the router? I see that the "IP

input" process and "ARP" process are taking 22 MB and 7 MB memory

respectively. If the device is covered under warranty, open a case with TAC

and they will be able to investigate and suggest IOS upgrade path.

Regards,

NT

Brandon Lynch Fri, 08/06/2010 - 08:21

Vitor,

I've looked at your memory outputs when the device was running low on available memory and we see the following -

Processor Pool Total:  177313232 Used:  151354108 Free:   25959124

...

86   0  109139980    7228060  101919124          0          0 IP ARP Adjacency

As you can see, the problem here is in the Processor pool and the majority of memory is being held by this ARP process.  I believe that your problem is this line in the configuration -

ip route 0.0.0.0 0.0.0.0 FastEthernet0/0

Pointing a static route to an interface as opposed to the next hop causes the interface and router to think that anything routed through that static route is directly connected and for that reason, we'll send an ARP request to the destination addresses that route through it.  You can read more about it here -

http://www.cisco.com/en/US/docs/ios/ipaddr/command/reference/iad_ip.html#wp1047008

"Adding a static route to an Ethernet or other broadcast interface (for example, ip route 0.0.0.0 0.0.0.0 Ethernet 1/2)  will cause the route to be inserted into the routing table only when  the interface is up. This configuration is not generally recommended.  When the next hop of a static route points to an interface, the router  considers each of the hosts within the range of the route to be directly  connected through that interface, and therefore it will send Address  Resolution Protocol (ARP) requests to any destination addresses that  route through the static route."

"...the router will consider all of the destinations  that the router does not know how to reach through some other route as  directly connected to Ethernet interface 1/2. So the router will send an  ARP request for each host for which it receives packets on this network  segment. This configuration can cause high processor utilization and a  large ARP cache (along with memory allocation failures). Configuring a  default route or other static route that directs the router to forward  packets for a large range of destinations to a connected broadcast  network segment can cause your router to reload."

This does not look like an IOS bug but a misconfiguration.  It is suggested that you change the static route to point to the next hop on the link, i.e. -

ip route 0.0.0.0 0.0.0.0

Make sure that you remove the static route that points to the Fa0/0 interface.  Let me know if you have any questions.  Also, I've published this document for general memory troubleshooting that you can use for future reference -

Troubleshooting MALLOCFAIL Errors and General Memory Problems

Hope this helps.

Brandon

ayokunles Tue, 06/04/2013 - 05:41

I am going to have to go back to this post after such a long time. but i think it sorted out my memory issues with my 2900 router...and I would say thanks..but its still under observation.

initially my router memory was up to like 70% but after changing that config, it brought it down to 21%.

jimmyc_2 Thu, 08/12/2010 - 07:45

We have a similar problem, what is the rule of thumb on processor memory?  I gotta think anything over 90% has to be investigated, but we have several routers in the 60 - 80% range.  Are they of immediate concern or just watch over a period of weeks to see trends (we use NetQos, if anyone has lessons learned)  thanks.

Amos Kafwembe Fri, 11/23/2012 - 05:23

hi guys.

i was doing an installation for a client and experienced this exact problem. did you guys manage to fix it when you had it?

y*** D*** Tue, 06/04/2013 - 10:46

I see that your doing Nat.
Check how many active translations you have.
The default timeout for Nat entry is 24 hours.
If you have over 30000 active entries change the timeout.
You can also verify with show process memory before and after clearing IP Nat translations.
I give tcp 5 minuts and Udovenko 30 seconds.
Verify with show IP Nat statistics


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