12 great new features in Cisco IOS 12.3

Cisco's IOS 12.3 and its sub-releases contain far more than basic incremental changes and bug fixes. Get a closer look at 12 of the most useful new changes, including Network Admission Control, Optimized Edge Routing, Dynamic Multipoint VPN, IPSec Stateful Failover, and more.

There may be a few network engineers out there who jump at the chance to upgrade Cisco routers to the latest software and drool on IOS release notes. However, I suspect that for most of you, "investigate and upgrade to the latest router IOS" is right up there with "reorganize file cabinet" and "clean out storage room." As a result, I am willing to bet that most of you haven't upgraded your routers to the latest version of Cisco IOS 12.3.

The first release of IOS 12.3 was in 2003. Since then, Cisco has made a number of minor releases that have included some very useful features. So, whether you don't have any idea what version of code you are running or you ran out and upgraded to 12.3 when it first came out and have ignored the subsequent releases, you should take a close look at the new features that are included in this IOS release.

I am going to highlight some of the major features included in IOS 12.3. I won't talk about the new IPv6 firewall that next-to-no-one is going to use. Below is a list of 12 features I found most important, but there are literally hundreds of other features. You can find out more about the various features in Cisco's IOS 12.3 documentation.


Author's note

The name of each of the new features is linked to Cisco's configuration documentation for that feature.


  1. Network Admission Control (NAC)
    Cisco's NAC runs on Cisco routers (running NAC on a switch is coming soon). With NAC, you also have client software on every PC on your network (the Cisco Trust Agent). A Cisco Secure Access Control Sever (ACS) is required to be on the network. Before the PC can have network access, its antivirus definition version is checked (you can have NAC check other software versions as well). If the PC does not have the required version, it is never given access to the network. Instead, it can be quarantined to a private network to perform the necessary upgrades. Microsoft has been working on a similar product called Network Access Protection (NAP). Fortunately, the two companies have gotten together to try to make their competing products compatible. For more information on that, read "Cisco and Microsoft Join Forces to Help Customers Address Security Threats."


  2. Intrusion Prevention System
    In IOS 12.0(5)T, Cisco introduced an Intrusion Detection System (IDS). This version offered only 59 signatures to identify intrusions. These signatures were not updateable. Thus, as new types of intrusions were developed, the IOS did not protect against them. In IOS 12.3(11)T Cisco now offers an Intrusion Prevention System (IPS) with 118 signatures. The important difference in the new IPS is that it allows customers to add new signatures as new attacks are developed. It does this by using a Signature Definition File (SDF), located on the router's flash. Customers can sign up for new IPS Alerts and read about existing alerts at Cisco's Intrusion Prevention Alert Center. When a packet comes through the router that matches a signature, the router can be configured to either alert the network administrator or drop the packet and send an alert. Cisco claims that, due to the new design, this can be done without affecting router performance.


  3. Optimized Edge Routing (OER)
    OER is a new feature that allows load distribution at the WAN edge. At my company, we have two T1 circuits to the Internet running BGP best-path routing. (I detailed this in "How to use BGP to achieve Internet redundancy.") While it does give us redundancy, it does a poor job of load balancing. This is because one provider is a Tier 1 and the other is a Tier 2. The Tier 1 provider almost always offers shorter paths and almost all the traffic goes across that circuit. We have tried to load-balance using weight and MED, but it doesn't always work. OER should be able to solve this type of load-balancing issue. With OER, you define the policy for your latency, throughput, and link cost parameters. The router uses this policy to determine how to balance the load across your multiple WAN links. Most likely, these are Internet links, but they could be other types of WAN links. OER supports both static routing and BGP. All this can be configured on the router’s IOS. If you want to have a graphical interface to control a more complex OER environment, you can buy an add-on OER Linux-based product called OER Master Controller Engine.


  4. Transparent Firewall
    Say that you want to add a firewall between two networks. Normally, just like a router, each interface of a firewall has to be on a different network. This sounds like a large network change, right? Perhaps it doesn’t have to be so complicated anymore. With IOS 12.3(7)T, Cisco introduced the Transparent Firewall. The benefits of the Transparent Firewall, as it works at Layer 2, are that it can be added to an existing network with minimal configuration, and it provides firewall security for that network. In fact, you can run a Layer 2 Transparent Firewall on the same router that's running the Layer 3 Firewall feature. In its most basic form, the Transparent Firewall works like this: You create a bridge group, put your interfaces in it, enable "ip inspect" (the firewall) on one of the interfaces, create an access-list that will be applied to the other interface, and voila, your Transparent Firewall is done.


  5. Warm Upgrade
    Warm Upgrade allows a running router to read an IOS image, decompress it, and immediately boot it. This keeps the router from having to shut down, go back to ROMMON, load the image, and decompress the image. Cisco says that this feature, which complements the Warm Reload feature introduced in IOS 12.3(2)T, will cut down the time for router reboot from four minutes to two minutes.


  6. AutoQoS for the Enterprise
    AutoQoS (Quality of Service) is a new feature that discovers the types of traffic on your network and the speeds of your interfaces, and then configures the proper network quality for that traffic according to best practices. This feature is primarily designed to assist in voice and video quality over the WAN but can be used for a variety of other things. AutoQoS can do in a few minutes what it could take a network expert a few hours to do. The downside is that AutoQoS is not full of options, it does not react to any future changes in the network, and once it is configured, you still need a network expert to analyze its results and make sure that it is working properly.


  7. AutoSecure
    AutoSecure analyzes your router’s security settings and can make changes for you. I won’t go into detail on AutoSecure because I wrote a full article on it for TechProGuild called "Automate Security Configurations with IOS 12.3."


  8. CallManager Express (CME) and Survivable Remote Site Telephony (SRST)
    CallManager Express (CME) has evolved from allowing a router to be a very limited, stand-alone, Voice-over-IP (VoIP) phone system to a nicely featured small to medium enterprise (SME) phone system (on a router). Concerning SRST, picture a large corporation that has a centrally managed CallManager (a Cisco VoIP phone system) with many remote locations. At these remote locations, the routers would have SRST configured so that if the WAN connection to the central CallManager was lost, the SRST-enabled router could provide limited calling features for the remote phones.


  9. Dynamic Multipoint VPN (DMVPN)
    Okay, you got me: Technically, this feature came out in 12.2(13)T, but it is so cool that I wanted to point it out. DMVPN allows routers to dynamically bring up, as needed, VPN tunnels to each other over the Internet. Better yet, these tunnels require only a very simple configuration. In the past, to create a fully meshed VPN network, there would have to be a fair amount of configuration on every router (or VPN concentrator) for every remote site. As the number of remote sites grew, these always-up VPN tunnels became very cumbersome to scale and the configurations were unmanageable. With DMVPN, a fully meshed VPN network can scale, and VPN tunnels are brought up only if needed.


  10. IPSecStatefulFailover
    This feature does exactly what it says it does. You have two routers, both with IPSec tunnels, being contacted on the LAN with Hot Standby Routing Protocol (HSRP). If one router goes down, in either a planned or unplanned situation, the backup router takes over and the IPSec tunnels never go down. While this has been available on higher-end VPN concentrators, including it free in the router’s IOS is a very nice addition.


  11. Network-Based Application Recognition (NBAR)
    Most routers just look at traffic at Layer 3. With NBAR, a router can look at Layers 4 through 7. That means that a router can recognize applications. Once it can recognize the applications, it can then take some action to ensure that that application gets higher priority, drop packets from that application, or take some other action. NBAR has been around since IOS 12.0, but it recognized only a small number of applications. What is new in IOS 12.3 is that NBAR can now recognize many more applications and new applications can be dynamically added using a PDLM (Packet Description Language Module). Cisco regularly releases new PDLMs for new applications. You can find that list at their PDLM Web page (valid CCO login required).


  12. Cisco Security Device Manager (SDM)
    SDM is a free Java management tool for routers. It requires IOS 12.2 or 12.3, depending on your router’s model. I did a full article on SDM so I won’t go into what it offers. For more information, check out the TechProGuild article "Use the free Cisco Security Device Manager to work with routers."

Final analysis

I hate to sound like those lawyers on TV commercials pitching their services, but here are some things you need to know:

  • Upgrading your IOS requires that you are either under Cisco SmartNet Maintenance program or you buy the latest IOS from a Cisco reseller.
  • Some of the features mentioned here are available only in certain versions of the IOS. That version of the IOS may not function on all routers due to CPU, RAM, and flash requirements. Visit the Cisco IOS Upgrade Planner (valid CCO login required) to see the latest version of the IOS that your router supports.
  • Once you know the latest IOS that your router supports, you can find out if the features you want are in that IOS. To do that, browse the release notes for that IOS at Cisco IOS New Feature Documentation.

Perhaps there are some features in IOS 12.3 that can make your life easier or make your network more secure. I have ordered additional flash memory for my core Internet router just to do the upgrade and get the OER routing. I hope that you find some of the new Cisco IOS features as exciting as I do. Upgrading your Cisco routers may seem like a pretty mundane chore, but the new features make it well worth the effort.