Getting started with Network Packet Generators

bit blaster

A friend of mine has just ordered a shiny new packet generator for his network lab. I’ve spent some time working as a QA engineer in a network lab and wanted to share some advice.

You can purchase stateful and stateless packet generators from major vendors like Spirent, IXIA or Agilent. If you just need to test throughput, latency or loss, a stateless packet generator will do the trick. The test hardware will use an ASIC to produce line-rate 10G traffic or higher. The Cisco Enterprise Testing Book calls this a ‘bit-blaster’ which I love. In the wrong hands it can also be a ‘network-melter’.  Continue reading

Link Utilisation Varies By Packet Size

I said to a colleague recently, “you can’t get 100% link utilisation on an Ethernet link”. When I tried to explain myself I wished I could link to a simple blog post with a nice graph. So here’s a quick blog post with a nice graph. I have talked a little about link speed in a previous post, but I wanted expand on this and add a quick graph to back up the argument.

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Running vEOS in GNS3

Virtualbox_Arista_Logos-whtbkA few weeks back I posted about my experience using VirtualBox to create running Arista vEOS instances. I loved how VirtualBox made is so easy to create VMs. However it seemed unwieldy and error prone to rely upon the VirtualBox console to attach each vEOS interface to a particular LAN segment. My last post explored using the CLI to create these mappings. I had planned to generate topologies using a script to create the appropriate vboxmanage commands at some later date.

I did manage to create a python script that read a topology file and create the right links between the VirtualBox vEOS VMs. I thought it would be cool to control that script via a GUI of some sort.  You know, like using GNS3 for drag an drop link creation. I downloaded the latest version of GNS3 to test IOS and noticed that it had a new VirtualBox category. Woot! Continue reading

Create a VirtualBox Arista vEOS image from the command line

Virtualbox_Arista_Logos-whtbkI’ve wanted to check out Arista EOS for a while, but didn’t have access to the hardware. I recently learned that Arista had made EOS available as a virtual machine. Arista call this vEOS. By installing the free VirtualBox hypervisor I could get vEOS running on my MacBook. It sounded a bit too easy, but to be fair the process is really well documented.

Before I go further I should say that I obtained my copy of vEOS from my local Arista SE. I don’t know of any formal way to get a copy but I’d be very surprised if Arista couldn’t provide one through your local sales team (read, don’t ask me to supply a copy). Once I obtained the bootloader iso and veos.vmdk image files I was ready to go. Continue reading

Test – Throughput alchemy using a snake topology

Sometimes it’s best not to trust network vendor datasheets.  Nothing quite beats a controlled test of a network device in your lab with your config and your required features. But if you want to load test multiple ports on your 10G device-under-test (or DUT), then things can get very expensive, very fast.  In this post I’ll show a test topology that will help you turn 10Gbps of test traffic into 640Gbps or more.

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OSPF – Setting MTU values for Cisco and Juniper

MTU mismatches are the primary reason an OSPF adjacency becomes stuck in the EXSTART state.  After hellos are exchanged and the routers become neighbors, each OSPF speaker advertises the IP MTU of it’s local interface in a Data Base Description (DBD) LSA.  If there is a mismatch you’ll probably just adjust the configuration to be identical on both ends of the link and be done. However, when you try to peer two OSPF routers with different network operating systems, things start to fall apart fairly quickly.

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