CCIE Home Lab, what to do when your router has too little Flash space for IOS

I already explained in an older post my home lab for CCIE preparation. My BB1-BB3 routers are Cisco 2600 series and the rest of R1-R6 are emulated with Dynamips. The only problem is that one of the C2600 has too little Flash space to hold the required IOS. Memory is sufficient, but Flash not.

The only workaround I have is to load the IOS image from a TFTP server. I will explain here my procedure, maybe it’s useful for somebody else out there.

First, I recently upgrade to Ubuntu 12.04 and for some reason the TFTPD (default tftp server) was not working properly. I found TFTPD-HPA to be a good alernative, so I did install it:

sudo apt-get install tftpd-hpa

After installation you may want to check /etc/default/tftpd-hpa. On my system it looks like this:

# /etc/default/tftpd-hpa


Next step is to get a IOS image and copy it under /var/lib/tftpboot. If you need a hint, I’m using c2600-adventerprisek9-mz.124-25d.bin which needs only a small amount of memory to be installed on the Cisco 2600 platform and it’s enough for testing.

Now we need to get the IOS image on the C2600 using TFTP. Depending on your topology used for CCIE exam practice, this can be done in different ways.

Currently I’m using the workbooks from Micronicstraining (Narbik’s workbooks, if this sounds more familiar). Previously I used the ones from Internetwork Expert. The idea is that topology is pretty similar and it looks something like this:

Narbik’s workbook topology

My problematic router is the BB3. Somehow I need that BB3 is communicating with my Ubuntu server, as simple as possible, without changing ethernet cables all the time.
You noticed int the above diagram that BB3 has an interface on the SW1 (Fa0/13) and SW1 has F0/1 connected to my Ubuntu server as explained in this post. What I need is to have Fa0/13 and Fa0/1 on the SW1 on the same VLAN for proper communication. Usually I just default the interface and then everything is fine.

On the Ubuntu box, I can have an IP address on the physical card (this will not influence in any way the Dynamips emulated router attached to this interface):

eth1      Link encap:Ethernet  HWaddr 00:e0:b6:06:a6:3b
          inet addr:  Bcast:  Mask:
          inet6 addr: fe80::2e0:b6ff:fe06:a63b/64 Scope:Link
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:64 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 B)  TX bytes:14100 (14.1 KB)

By default on the BB3 router I have an IOS image that can fit the Flash size (c2600-i-mz.123-26.bin) and in case that for some reasons the TFTP Server is not reachable, it will boot that image.

The BB3 startup-configuration looks like this:

interface FastEthernet0/0
 ip address
boot system tftp c2600-adventerprisek9-mz.124-25d.bin

What you have to remember:
1. Start your TFTP server and assure that it has the correct IP address on the interface where you will server IOS files
2. Start your switch (if you have one in between Cisco router and the TFTP server) and be sure that the interfaces are able to exchange packet (same VLAN, etc)
3. Start your Router

In case you did miss any of the above steps, you’ll see something like this:

%SYS-4-CONFIG_NEWER: Configuration from version 12.4 may not be correctly understood
 Slot is empty or does not support clock participate
 WIC slot is empty or does not support clock participate
%SYS-6-READ_BOOTFILE_FAIL: tftp:// File read failed -- Timed out.

 Hello from IFS_TYPE_ROM successful type-check

%SYS-6-BOOT_MESSAGES: Messages above this line are from the boot loader.
boot of "tftp:c2600-adventerprisek9-mz.124-25d.bin" using boot helper "flash:c2600-i-mz.123-26.bin" failed
error returned: File read failed -- Timed out
loadprog: error - on file open
boot: cannot load "tftp:c2600-adventerprisek9-mz.124-25d.bin"

and the router will boot your image stored locally on Flash.

Instead of doing all this work, which may generate some headache, I could just buy another router with enough Flash (and Memory). Currently I don’t want to make this investment, so I’ll stick with the above scenario.

Cisco IOS release naming

Most probably you already know this, but for those who are interested, here is a list of the letter definitions for Cisco IOS release trains. In more human terms, if you have loaded an IOS image like c2900-universalk9-mz.SPA.150-1.M5.bin, what those letters (in this case SPA) mean:

  • A = Aggregation/Access Server/Dial technology
  • B = Broadband
  • C = Core routers (11.1CA, 11.1CT, 11.1CC)
  • D = xDSL technology
  • E = Enterprise feature set
  • F = Feature Specific enhancements (11.2F)
  • G = Gigabit Switch Routers (GSR)
  • H = SDH/SONET technology (11.3HA)
  • J = Wireless Networking technology (Aironet)
  • M = Mobile (Restricted to Mobile Wireless BU usage and further reserved for Mainline)
  • N = Voice, Multimedia, Conference (11.3NA)
  • P = Platform features (11.2P)
  • R = Reserved for ROMMON reference
  • S = Service Provider
  • T = Reserved for Consolidated Technology Train
  • W = LAN Switching/Layer 2 routing
  • X = A short lived, one-time release (12.0XA)
  • Y = A short-lived, one-time release (when Xs are exhausted)
  • Z = A short-lived, one-time release (reserved if Ys are exhausted)

Additional information can be found here.

Petition for Educational Cisco IOS emulator

Sign Educational Petition

The Cisco IOS Emulator Petition

We the undersigned ask Cisco to consider our petition for an open and usable IOS Emulator for learning, study and training.

We are the people who are learning about Data networking and Cisco IOS software. As students and practitioners, we need to learn theory and knowledge and then to take that knowledge and practice on Cisco IOS software.

We want to be able to practice that knowledge, and demonstrate our competence. We know that you are considering the value. This petition is to show our need for this solution. Wendel Odom discusses the possibility Cisco Considers IOS for Certifcation Self Study and we are calling for Cisco to make an option available.

This experience and knowledge we gain gives us the capability to make the most of Cisco equipment for our employers, your customers. We help drive the best return on investment, and keep the network performing in the way that your customers expect.

We can test configurations prior to making and be better prepared. We can develop more complex configurations than would otherwise be possible, and not blame the equipment afterwards.

We resolve problems more quickly, we make better designs and we have greater confidence in our work. We raise less support cases (and reduce your costs) by being to perform our own testing and validation.

Whether we are resellers, consultants, students or just interested in learning, we all need an practical method to access IOS and practice.

Therefore, we are asking Cisco Systems to make a version of IOS available for educational and testing purposes.

by Greg Ferro at Etherealmind

Please sign this petition. Together we can be strong!

Cisco: Prioritize Voice traffic with LLQ

In one of my previous posts I was explaining how to mark packets closer to network edge. Starting from that point, we are sure the packets are market with the correct value, so on the router device we can directly match those packets and prioritize using Low Latency Queueing.

I believe you already know why queueing is so important for Voice packet especially, but also for all other kind of real time protocol (e.g. Video over IP), but just a small reminder. Most of the interfaces are using FIFO method for queuing. This is the most basic queue method and as you probably know means First In First Out. In human terms, first packet how arrive on the interface will be send first. Nothing wrong with this theory until this point and I can assure you that most of the time you don’t have to do anything to improve this technique. But what if you have real time protocols (e.g. voip services) and data transfer over the same physical interface? With FIFO the packets are sent out the interface as they arrive, but this is not very good for the delay sensitive traffic like voice. If a TCP packet in HTTP flow can wait it’s turn to be sent out, with not visible impact for user, than a delayed voice packet will cause deprecation in voice call.

With this problems need to be solved we arrive at LLQ, which is an ehanced version of Priority Queueing (PQ) in a Class-Based Weighted Fair Queueing (CBWFQ).

Before we start let’s have a look to the topology we will use (the same like in Cisco: Mark voice packets at the network edge post):

After marking the packets on the Access Switch,now we want to prioritize voice packets on the core router:

1) Match packets market with EF in a class-map

class-map VOICE
match dscp 46

2) Configure a policy-map unde which you match the traffic in the class-map VOICE and enable LLQ. The parameter “priority” is the one telling policy-map to enable priority queueing under that class. The value after the “priority” keyword can be a value in kbps or percentage from the total bandwidth. In the example below I assume that I have a 10Mbps bandwidth and I’ll configure LLQ class to use 10% from it, meaning 1000kbps

policy-map MYPOLICY
class VOICE
priority 1000

or with percentage

policy-map MYPOLICY
class VOICE
priority percent 10

I have to tell you that after the bandwidth or percent value you can add a burst value in bytes. If you don’t add this value, it will be calculated automatically. I chose this method when I’m doing simple config, but if you want to fine tune the values you can calculate it yourself and add it. Be careful that a higher value will influence the Tc value in the process.

3) Apply the policy to the WAN interface of the Core router (I assumed that the Core router is your direct connection to provider backbone) direction outbound. You cannot apply this type of queueing direction inbound. Keep this in mind.

interface s0/0
service-policy output MYPOLICY

If you insist on applying it inbound, you’ll get an error message:

Core(config-if)#service-policy input MYPOLICY
Low Latency Queueing feature not supported in input policy.

To check that your queueing policy is applied:

show policy-map interface s0/0

Service-policy output: MYPOLICY

queue stats for all priority classes:

queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 0/0

Class-map: VOICE (match-all)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: EF
Priority: 10% (1000 kbps), burst bytes 25000, b/w exceed drops: 0

Class-map: class-default (match-any)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any

queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 0/0

10 Cisco IOS Router file management commands every Cisco admin should know

Well this is the most CIsco IOS basics commands and perhaps useful for some of you, who are beginning to experience with this products.

The following Cisco IOS commands explained in the video below are used for file management:

dir, cd, copy, delete, rm, show flash, erase, format, more, verify, mkdir, fsck

The tutorial is work of Bill Detwiler at