1811 Memory Running low

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May 29th, 2008
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I have a relatively new 1811 router and it seems like every other day the memory is completely full and no one is able to transfer any data on the network until it is restarted. The unit has the standard 128 MB ram running IOS 12.4(6)T10. Any suggestions would be greatly appreciated.

Correct Answer by Sushil Kumar Katre about 8 years 11 months ago

Hi Brandon,


Please change the following route statement -

ip route 0.0.0.0 0.0.0.0 FastEthernet0


Instead of pointing the route to fa0 point it to next hop IP address.


This statement must be causing ARP request to be generated on the ethernet for every destination the router finds through the default route because the router considers all of these destinations as directly connected to FA0.


http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800ef7b2.shtml


-> Sushil

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Mark Yeates Thu, 05/29/2008 - 15:24
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Brandon,


What kind of load is the router under at normal/peak times? Another helpful thing you can try to figure out the problem by issuing the "show processes memory sorted" command and see which tasks are taking up the most memory before you reboot the router. That way you can find out if it is a network issue or a bug in the IOS. If all else fails you can upgrade to a newer IOS.



HTH,

Mark

Joseph W. Doherty Thu, 05/29/2008 - 17:25
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One way to free up RAM, sometimes significant amounts, is run an IOS with a smaller footprint. This can often be accomplished by using an IOS with the minimal feature set necessary and/or running an earlier version of the IOS. An example of the former might be the IP Base feature set; an example of the latter might be a 12.4 version vs. your 12.4T version.


Something else to check for is memory resource usage that might be unnecessary. For example, using a large syslog memory buffer (show log will indicate if syslog memory buffer active and its configured size).


A very advanced technique is to configure the ERM memory monitor to notify router process when there's a low memory situation (i.e. where they will hopefully minimize their usage upon the notification).



Brandon0238 Fri, 05/30/2008 - 07:01
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ARP input and chunk manager are using the largest bits of memory

Sushil Kumar Katre Mon, 06/02/2008 - 22:54
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Brandon,


Please upload the running configuration from the router if opssible.


-> Sushil

Correct Answer
Sushil Kumar Katre Tue, 06/03/2008 - 20:16
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Hi Brandon,


Please change the following route statement -

ip route 0.0.0.0 0.0.0.0 FastEthernet0


Instead of pointing the route to fa0 point it to next hop IP address.


This statement must be causing ARP request to be generated on the ethernet for every destination the router finds through the default route because the router considers all of these destinations as directly connected to FA0.


http://www.cisco.com/en/US/tech/tk365/technologies_tech_note09186a00800ef7b2.shtml


-> Sushil

Brandon0238 Wed, 06/04/2008 - 05:16
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Seems like the perfect solution so far. Browsing has sped up 100%. Thanks so much to you all for helping this newbie!

Sushil Kumar Katre Wed, 06/04/2008 - 07:27
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Great to hear that Brandon. I learnt this issue in a very hard way :)


-> Sushil

Brandon0238 Wed, 06/04/2008 - 07:36
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Well, I appreciate you taking the time to answer my question.


Update: Free memory has gone from 39/128 to 45/128. All appears to be well! Thanks again!

Sushil Kumar Katre Sat, 06/07/2008 - 11:18
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Hey Brandon, how's your buddy [router]? no more trouble?


-> Sushil

Brandon0238 Sun, 06/08/2008 - 05:53
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Router is working great! Browsing the Internet is fast, and memory is staying constant at 44/128 MB free. Thanks so much for your help!

Joseph W. Doherty Wed, 06/04/2008 - 02:31
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Sushil's notice of your using a default route to an interface within your config instead of a next hop could explain you large ARP RAM allocation; especially one that would grow as time goes by. (Each outbound Internet IP address would ARP. The ARP entries would eventually time out, but the default takes a while. You might be able to adjust the ARP time out timer, but Sushil's suggestion is much better since it avoids the problem. Simple change, worth trying.)

sirdudesly Tue, 06/03/2008 - 21:07
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I'd also suggest picking up some extra ram for it as well, the ram to suit an 1800 series is relatively cheap.



My 1803 (i'm a little bit down market) at home with a 10mbit cable connection hanging off FE0 and all the usual bells and whistles running (firewall etc) and 3 hosts directly connected and a wireless gateway sits on about 60% memory used.

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