Modular IOS

[Jason Masker]

Anyone have current experience with Modular IOS? It has been a few years since this feature set was released. Is the code fairly stable now? We are doing device upgrades for our core routers and I could see where we may benefit from modular even though we have redundant cores, but I thought I would solicit some feedback from the community first.

Jason

[Jon Marshall · Accepted solution]

Jason

Which devices are you referring to ? If 6500 then it is my understanding that Cisco are phasing out modular IOS for these devices so it may not be a good idea to upgrade to a modular version.

Jon

[Jason Masker]

Jon

That would be a good reason not to go modular. Is there any published documentation of Cisco's intent? I see they still include a recommended modular version in their safe harbor testing.

Jason

[Leo Laohoo]

Talk to your Cisco SE.  They'll have the info.

[Jon Marshall · Accepted solution]

jasmasker wrote:
Jon
That would be a good reason not to go modular. Is there any published documentation of Cisco's intent? I see they still include a recommended modular version in their safe harbor testing.
Jason

Jason

I actually picked up on it through these forums eg -

https://supportforums.cisco.com/message/3199915#3199915

I haven't seen any official statement from Cisco but it may well be worth having a chat with them about it if you have access.

Jon

[Jason Masker]

Thanks, Jon. Do you have any feedback on SXI versus SXH? I see they have safe harbor for both and SXI has also been out for a while now.

[Jon Marshall]

Jason

No direct experience of SXI but have used Safe harbor versions before and found them to be reliable so if they have an SXI version and i was looking to upgrade i would probably go for that version. The less times you have to actually upgrade the better. Plus as an added incentive Cisco have just released an EoS/EoL announcement for 12.2(33)SXH -

http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/eol_c51-624522.html

Obviously release notes need checking just in case some modules/features you need are no longer supported.

Jon

[Reza Sharifi]

Jason,

If you do a comparison between SXH and SXI, you will find out that SXI has a lot more knobs and features specially when it comes to MPLS, IPv6 and VSS.

Overall most feature are being implemented in SXI.  In addition to what Jon already noted about the modular vs none-modular, starting in 2012 the new releases of IOS will not have modular option any more.  Of course this is according to 6500 BU, but as you know thing can change between now and 2012.

I would recommend none-modular, as I really do not see any benefit in modular releases.  Again according to Cisco since they do not see a lot of demand for modular IOS, they are slowly phasing them out.

HTH

Reza

[lamav]

Hi:

Modular IOS is not a feature set; it's a software architecture in which processes are modularized to prevent detrimental dependencies on each other. So, if one component of the IOS code fails, the others may continue running without interruption. So, I am not sure what anyone means when they say that modular IOS does not provide any advantages. It does - plenty. And while it may be getting phased out on the 6500 platform, I dont think it is in general. It's quite the opposite.

Lastly, Juniper's claim to fame with their JUNOS has always been that it is modularized and therefore much more stable and reliable than Cisco's IOS. That's why the goal of Cisco's latest variants -- IOS XR, IOS XE and NX-OS — is to overcome the monolithic limitations of  the traditional IOS while addressing critical needs for increased uptime and availability. All these operating systems are modular, in that IOS services run as  modules on top of a Linux-based kernel (in IOS XE and NX-OS), or as a third-party Portable-Operating-System-Interface (POSIX)-based  real-time kernel (in IOS XR).

Victor

[Jason Masker]

Thanks for the response, Victor. I understand what Modular IOS is and I am very interested in the benefits--that is why I was asking for feedback. However, I do not want to deploy an image that is on notice.  I understand modularity is a significant architectural change of the OS deserving of much more flattering and flowing language than "feature." Don't read too much into it. I was merely referring to the way Cisco has chosen to deploy it. When I click on the download page of a particular version of IOS, I can choose between IP Basic, IP Advanced Services, IP Advanced Services (modular), etc. Traditionally the choice at this point is a choice between "feature sets" but I suppose now it is a choice between feature sets/architectures--at least, apparently, until Cisco phases out the modular images.

Thanks to everyone for the comments. Based on what has been shared I think I'll skip worrying about software modularity as it is of only marginal benefit with redundant equipment, SSO, etc. and probably not worth messing with if there is a question of future availability of the platform.

Jason

[Giuseppe Larosa]

Hello Jason,

the reason for low demand on modular IOS on C6500 is that it suffers of some bugs at least in 12.2(33)SXH you can find many threads in the forums where high cpu usage is seen on devices doing nothing special or related to telnet sessions

When I have seen this I strongly recommended to my customer to remove modular IOS from new C6500 and to use 12.2(33)SXH before and 12.2(33)SXI now.

Many other people have done the same.

stop.

Hope to help

Giuseppe