Archive for November, 2010
In this first of a series of blog posts regarding Catalyst QoS, we will exam the AutoQoS capabilities on the 3560 Catalyst devices. AutoQoS allows for the automation of QoS settings for the switch with an absolute minimum of configuration required from the engineer. In particular, the 3560 AutoQoS features automates the classification and congestion management configurations required in VoIP environments. You should note that the 3560 AutoQoS has much “catching up” to do when you compare this feature to AutoQoS for VoIP and AutoQoS for Enterprise that are both now possible in the pure router class of Cisco devices.
First, the easy part. The interface configuration command required for QoS is simply:
auto qos voip [cisco-phone | cisco-softphone | trust]
Notice the auto qos voip command is used in conjunction with keywords that specify what devices to “trust” when it comes to these important VoIP packets. The cisco-phone keyword instructs the AutoQoS feature to only trust and act upon the incoming voice packets if they are truly sent from a Cisco IP Phone. The phone’s presence is detected thanks to CDP. Similarly, the cisco-softphone keyword instructs the device to only trust and act upon the voice packets if they are sent from a Cisco phone running in software on a PC. Finally, the trust keyword instructs the device to trust markings for VoIP packets that are coming from another switch or router over the port.
Just as with the CCDP, Cisco has delayed the release of the new DESGN exam. The DESGN exam (640-864) is expected to be available on December 16, 2010.
Here are the topics promised fro the new exam:
Describe the Methodology used to design a network
- Describe developing business trends
- Identify Network Requirements to Support the Organization
- Describe the tools/process to characterize an existing network
- Describe the top down approach to network design
- Describe Network Management Protocols and Features
Describe network structure and modularity
- Describe the Network Hierarchy
- Describe the Modular Approach in Network Design
- Describe network architecture for the enterprise
Worried about topics like EEM, OER, IP SLA, SNMP and the seemingly endless list of Network Services that might appear in your CCIE R&S (or related track) Lab or Written Exam? The latest of the 3 Day Technology Bootcamps arrives just in time for the new year.
The 3-Day Network Services bootcamp will be help Live Online on Dec 27-29, 2010. Class will run each day from 11 AM EST US to approximately 6 PM EST US. We hope to see you in the Live Event, but a Class-On-Demand version will be available the week following.
In our CCDP bootcamp, we examined Cisco’s implementation of Virtual Private LAN Services (VPLS) in some detail. One blog that I promised our students was more information about how large enterprises or Internet Service Providers can enhance the scalbility of this solution.
First, let us review the issues that influence its scalability. We covered these in the course, but they are certainly worth repeating here.
Remember that VPLS looks just like an Ethernet switch to the customers. As such, this solution can suffer from the same issues that could hinder a Layer 2 core infrastructure. These are:
- Control-plane scalability – classic VPLS calls for a full-mesh of pseudo-wires connecting the edge sites. This certainly does not scale as the number of edge sites grow – from both operational and control-plane viewpoints.
- Network stability as the network grows – Spanning Tree Protocol-based (STP) infrastructures tend not to scale as well as Multiprotocol Label Switching (MPLS) solutions.
- Ability to recover from outages – as the VPLS network grows, it could become much more susceptible to major issues for customer connectivity in the result of a failure.
- Multicast and broadcast radiation to all sites – remembering that the VPLS network acts as a Layer 2 switch reminds us that multicast and broadcast traffic can be flooded to all customers across the network.
- Multicast scalability – multicast traffic has to be replicated on ingress PE devices, which significantly reduces forwarding efficiency.
- IGP peering scalability issues – all routers attached to the cloud tend to be in the same broadcast domain and thus IGP peer, which results in full-mesh of adjacencies and excessive flooding when using link-state routing protocols.
- STP loops – it is certainly possible that a customer creating an STP loop could impact other customers of the ISP. STP may be blocked across the MPLS cloud, but it is normally used for multi-homed deployments to prevent forwarding loops.
- Load-balancing – the use of MPLS encapsulation hides the VPLS encapsulated flows from the core network and thus prevents the effective use of ECMP flow-based load-balancing.
A popular task in CCIE-level scenarios requires creating an access-list matching a set of prefixes using the minimum number of access-list entries. Typically, such scenarios were relatively easy, so figuring out a combination of subnet prefix and wildcard mask was more or less intuitive. However, a good question would be if there exist a generic algorithm for constructing such “minimal” access-lists. To give you a better feel of the problem, let’s start with an example. Look at the following access-list matching nine different subnets:
ip access-list standard TEST permit 220.127.116.11 permit 18.104.22.168 permit 22.214.171.124 permit 126.96.36.199 permit 188.8.131.52 permit 184.108.40.206 permit 220.127.116.11 permit 18.104.22.168 permit 22.214.171.124
Have you ever been on your GradedLabs rack of equipment and wanted to test a particular feature or set of configurations, but you certainly do not want to keep these changes on the rack? Perhaps this is because you are right in the middle of solving a Volume 2 lab and you certainly cannot have that configuration impacted.
Thanks to the very handy config replace command, you can easily rollback almost instantly to your previous saved configuration after your experimenting. Here is a demonstration of just how simple this is. Enjoy, and let us give thanks for all there is to learn on blog.ine.com! I also want to thank my good friend Keith Barker for first showing me this one.
Rack29R1#configure terminal Enter configuration commands, one per line. End with CNTL/Z. Rack29R1(config)#hostname TEST TEST(config)#interface fastethernet0/0 TEST(config-if)#ip address 126.96.36.199 255.0.0.0 TEST(config-if)#no shut TEST(config-if)#end TEST# TEST#config replace nvram:startup-config force Total number of passes: 1 Rollback Done Rack29R1# Rack29R1#show run interface fa0/0 Building configuration... Current configuration : 83 bytes ! interface FastEthernet0/0 no ip address shutdown duplex auto speed auto end Rack29R1#
BGP (see ) is the de-facto protocol used for Inter-AS connectivity nowadays. Even though it is commonly accepted that BGP protocol design is far from being ideal and there have been attempts to develop a better replacement for BGP, none of them has been successful. To further add to BGP’s widespread adoption, MP-BGP extension allows BGP transporting almost any kind of control-plane information, e.g. to providing auto-discovery functions or control-plane interworking for MPLS/BGP VPNs. However, despite BGP’s success, the problems with the protocol design did not disappear. One of them is slow convergence, which is a serious limiting factor for many modern applications. In this publication, we are going to discuss some techniques that could be used to improve BGP convergence for Intra-AS deployments.
BGP-Only Convergence Process
Tuning BGP Transport
BGP Fast Peering Session Deactivation
BGP and IGP Interaction
BGP PIC and Multiple-Path Propagation
Practical Scenario: BGP PIC + BGP NHT
Considerations for Implementing BGP PIC
Appendix: Practical Scenario Baseline Configuration
Cisco originally promised us a new CCDP exam (version 2.1) on Nov 8, 2010.
That date is now moved to December 23, 2010. Our Class On Demand was designed to cover you for the old blueprint and the new, so there should be no concern for students. Of course we will be taking the new exam the week following its release and we will be sure to provide any updates to the course that may be required free of charge.
In the meantime, watch blog.ine.com for many posts regarding valuable extra technical information regarding this popular new course. I also want to send out one more thank you to the many students we had that were active participants in the live event. It was an honor to have so many Cisco employees join us, as well as the many highly motivated students from around the world.
Here is the recommended reading list that several asked for from our CCDP Bootcamp. Thanks again to all that attended for the awesome participation and discussions.