What Router IOS should I use...best practices

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Feb 13th, 2008

Where can I find downloads for general deployment releases for routers. When I go to the software download area I just se LD and ED releases. Also can someone tell me what risks there are with ED or LD releases and what is best practice...to use GD, LD, or ED....to maintain a stable environment?



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JORGE RODRIGUEZ Wed, 02/13/2008 - 08:21


Best practice may depend from custumers need to utilized new feature sets or fix a bug in their current running IOS affecting router's performance or network performance, the best practice link bellow at the end will assist you in deciding why and when to upgrade, the decition should be based on following basic guidelines as well as getting aquainted with

http://tools.cisco.com/security/center/home.x for security alerts and your current decvices IOS's and their known bugs in bug tools database, check security advisory,

check security notices and Deferral Advisory all these can be found at


For all your other LD, GD and AD questions this pdf will have detail information on it.


Best Practice theory for IOS upgrade




burleyman Wed, 02/13/2008 - 08:36

Thanks...those were great links. I did go to the software donload page and I did not see any GD releases, are those somewhere else. I am looking for the latest GD release for a 2821 router. I see 2800nm-advipservicesk9-mz.124-18 but it says it is LD.


JORGE RODRIGUEZ Wed, 02/13/2008 - 09:57

Mike, you are correct there are no GDs for any of the 2800 series, I do not have the answer why, perhaps someone from forum or TAC may commnent on why.



Joseph W. Doherty Wed, 02/13/2008 - 18:19

GD (General Deployment) is determined by Cisco when it believes the release is mature enough to be generally deployed. (Hope the last doesn't seem too circular.)

When this happens varies. (Basically Cisco believes at this milestone the IOS is very stable and solid.)

12.4 hasn't reached this milestone yet.

Joseph W. Doherty Wed, 02/13/2008 - 20:15

With regard to stability, GD is the mainline successor to LD, so it should be, and is Cisco believed to be, unlikely to encounter problems.

ED variants encompass all type of changes, and because of the changes, might be, although don't have to be, less stable than a mainline LD/GD.

For stability, generally software that's further along in its lifecycle (time wise), and widely utilized, is less likely to have problems. So although within the same software version (e.g. 12.3) GD >= LD >= ED, between software versions, a late (e.g. 12.3) ED might be better than a new (e.g. 12.4) LD.

Paolo Bevilacqua Thu, 02/14/2008 - 09:08

In my opinion, the GD concept never made much sense and retirement of it is a good pragmatic choice by cisco.

At the time a release reached GD status, invariably it lacked the SW features or HW support to do what customer wanted in important deals and to fend competition.

So the choice was always, either run ED, or do it on old hardware with clumsy setups, or don't do it all.

Neither to say that customers running GD have never been affected by nasty bugs.

What really matters is that cisco improves testing on all releases instead.

burleyman Thu, 02/14/2008 - 09:50

By what little bit I just learned I would agree. I am trying to pay more attention to what IOS we are running instead of just leaving what they come with. Would you say it would be best to stay away from T releases and stick with the maintenance releases? unless the T releases fix a specific problem or has a upgrade you need. Also, how often do you update you router and switching enviroment?



Paolo Bevilacqua Fri, 02/15/2008 - 09:20

Yes, I would agree with that.

Then it depends how much you care about having new features in the network. Some people really don't, others like to be living the on the edge.

Danilo Dy Fri, 02/15/2008 - 09:33


When to update is you have to set your own maintenance window, this includes urgent (security fix). If is better to upgrade during maintenance period/window before you experience the problem (if your IOS is affected and you are using the feature that is directly affected) during production period which will affect your SLA if you have - beside the headache.



paul.matthews Mon, 02/18/2008 - 08:23

I alsways advised that where possible a recent GD version, as that automatically put one on a mainline version with most of the major or "obvious" bugs sorted. Unfortunately 12.4 sees the end of GD.

Were possible I also advise against the use of T or X releases. Xs are typically to get new gardware out as quickly as possible. T trains are where new features first see the light of day. That means they don't yet have large amounts of hours behind them.

X versions are normally ED as are T trains, so LD is preferable.

The simple version of what I would normally recommend is at the moment I would (without any major reasons to use something else) go for the latest 12.3 GD version.

Look up safe harbor - that may help with choiced.


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