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Recognizing IP MTU Issues

At some point, Network engineers will likely face some type of issue with MTU or maximum transmittable unit. Their first experience with this may be an eye opening and time consuming effort. After resolving the issue, those with a thirst for knowledge will take the necessary time to understand the issue.

MTU problems are most often seen when Path MTU Discovery, or PMTUD, fails to function. This is the process by which one end host determines the largest possible packet size to another station on the network. Symptoms of this type of issue include two devices having proven reachability, but applications fail to work in a way that indicates a network issue. Some applications may even crash or hang the system.

Symptoms of PMTUD Failure

• Hosts may be able to ping one another
• Service/Port may prove accessible using telnet
• Severe and persistent application issues
• Partial page loads
• Either host appearing to hang

Understanding IP MTU

To understand the problems of Path MTU Discovery, it is first necessary to understand how MTU relates to the conversation. MTU, or maximum transmittable unit, is the maximum chunk of data that a given interface can transmit. The type of data receiving our attention is IP Continue reading

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Some Internet Measurements

At APNIC Labs we’ve been working on developing a new approach to navigating through some of our data sets the describe aspects of IPv6 deployment, the use of DNSSEC and some measurements relating to the current state of BGP.

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Handling “Multiples” in Cisco NX-API with Python

A few weeks ago, I was working with the NX-API currently found on Cisco’s Nexus 9000 series switches, and ran into some peculiar behavior.

NX-API returns all information in terms of Tables and Rows. For a specific example, let’s look at what NX-API returns when I ask the switch for running OSPF processes:

There’s actually a lot more information in this snippet that pertains to the OSPF process itself, but I have omitted it for brevity. This specific example focuses on the section that describes the areas in this OSPF process.

{
  "ins_api": {
    "sid": "eoc",
    "type": "cli_show",
    "version": "0.1",
    "outputs": {
      "output": {
        "code": "200",
        "msg": "Success",
        "input": "show ip ospf",
        "body": {
          "TABLE_ctx": {
            "ROW_ctx": {
              ### OSPF process information omitted for brevity ###
              "TABLE_area": {
                "ROW_area": {
                  "age": "P15DT15H27M6S",
                  "loopback_intf": "1",
                  "passive_intf": "0",
                  "last_spf_run_time": "PT0S",
                  "spf_runs": "9",
                  "lsa_cnt": "5",
                  "no_summary": "false",
                  "backbone_active": "true",
                  "stub": "false",
                  "aname": "0.0.0.0",
                  "total_intf": "2",
                  "auth_type": "none",
                  "act_intf": "2",
                  "nssa": "false",
                  "lsa_crc": "0x18d91"
                }
              }
            }
          }
        }
      }
    }
  }
}

NXAPI uses a special tag that starts with TABLE, and within that, tag(s) that start with ROW, whenever it needs to describe something that would normally be Continue reading

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Understanding IPv6: Link-Local ‘Magic’

Denise Fishburne performs a little IPv6 sleight of hand in the second post in her series on IPv6.

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Working with VMware NSX – Logical networking

In my last post, we wrapped up the base components required to deploy NSX.  In this post, we’re going to configure some logical routing and switching.  I’m specifically referring to this as ‘logical’ since we are only going to deal with VM to VM traffic in this post.  NSX allows you to logically connect VMs at either layer 2 or layer 3.  So let’s look at our lab diagram…

If you recall, we had just finished creating the transport zones at the end of the last post.  The next step is to provision logical switches.  Since we want to test layer 2 and layer 3 connectivity, we’re going to provision NSX in two separate fashions.  The first method will be using the logical distributed router functionality of NSX.  In this method, tenant 1 will have two logical switches.  One for the app layer and one for the web layer.  We will then use the logical distributed router to allow the VMs to route to one another.  The 2nd method will be to have both the web and app VMs on the same logical layer 2 segment.  We Continue reading

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Quick’n’dirty Nslookup BASH Script

I’m always wondering if the addresses I’m assigning to interfaces aren’t already in DNS. So I came up with a little BASH script that takes a list of IP addresses and performs an nslookup on them to ensure they’re not in use already:

$nslookup < input-filename > output-filename

The addresses in the input file are carriage return delimited.

A better use for this would be to check if DNS entries already have an IP address assigned to them.

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Handling “Multiples” in Cisco NX-API with Python

A few weeks ago, I was working with the NX-API currently found on Cisco’s Nexus 9000 series switches, and ran into some peculiar behavior. NX-API returns all information in terms of Tables and Rows. For a specific example, let’s look at what NX-API returns when I ask the switch for running OSPF processes: There’s actually a lot more information in this snippet that pertains to the OSPF process itself, but I have omitted it for brevity.

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Handling “Multiples” in Cisco NX-API with Python

A few weeks ago, I was working with the NX-API currently found on Cisco’s Nexus 9000 series switches, and ran into some peculiar behavior. NX-API returns all information in terms of Tables and Rows. For a specific example, let’s look at what NX-API returns when I ask the switch for running OSPF processes: There’s actually a lot more information in this snippet that pertains to the OSPF process itself, but I have omitted it for brevity.

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27 – Stateful Firewall devices and DCI challenges – Part 1

Stateful Firewall devices and DCI challenges

Having dual sites or multiple sites in Active/Active mode aims to offer elasticity of resources available everywhere in different locations, just as with a single logical data center. This solution brings as well the business continuity with disaster avoidance. This is achieved by manually or dynamically moving the applications and software framework where resources are available. When “hot”-moving virtual machines from one DC to another, there are some important requirements to take into consideration:

• Maintain the active sessions stateful without any interruption for hot live migration purposes.
• Maintain the same level of security regardless the placement of the application
• Migrate the whole application tier (not just one single VM) and enable FHRP isolation on each side to provide local default gateway (which works in conjunction with the next bullet point)
• While maintaining the live migration, it can be crucial to optimise the workflow and reduce the hair-pining effect as much as we can since it adds latency.  As such, the distances between the sites as well as the network services used to optimize and secure the multi-tier application workflows amplify the impact of performances.

As with several other network and security services, the Continue reading

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Everything can be a bomb

This last week, pranksters replaced the US flag on top the Brooklyn Bridge with a white-flag. Nobody knows who or why. Many in the press have linked this to terrorism, pointing out that it could've been a bomb. Not only local New York newspapers have said this, but also CNN.

Such irrational fears demonstrate how deeply we've fallen for police-state fears, where every action is perceived as a potential terrorist threat.

It could've been a bomb, of course. But what could also have been a bomb is a van full of C4 explosives driven across the bridge. There are no checkpoints at either end inspecting vehicles with bomb sniffing dogs. What also could've been a bomb is a ship full of fertilizer that, when ignited, would act as a small nuke. The point is that everything can be a bomb. Instead of using this as justification for an ever increasing police-state, we just need to accept this and live with the danger -- because this danger is, in the end, tiny. A thousand 9/11 events would still not equal cancer, for example.

I mention this because the former 9/11 commission released a new report yesterday stoking the fears of cyber-terrorism, Continue reading

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Configuring NetFlow on vSphere 5.5

The NetFlow protocol was developed by Cisco to collect traffic statistics. An enabled NetFlow device send to a NetFlow receiver a set of flows via UDP protocol. Each NetFlow contains one or more records: Input and output interface index Timestamps Number of bytes and packets observed in the flow Source and destination IP addresses Protocol, source […]

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Um, talks are frequently canceled at hacker cons

Talks are frequently canceled at hacker conventions. It's the norm. I had to cancel once because, on the flight into Vegas, a part fell off the plane forcing an emergency landing. Last weekend, I filled in at HopeX with a talk, replacing somebody else who had to cancel.

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How to run Juniper Firefly Perimeter vSRX on GNS3

Firefly Perimeter is a virtual security appliance that provides security and networking services at the perimeter in virtualized private or public cloud environments. It runs as a virtual machine (VM) on a standard x86 server  and delivers similar security and networking features available on branch SRX Series devices.

However not all the features that are supported by SRX hardware devices are supported. Here is the list of features supported by current firefly 12.1x46-d10 release.

Firefly Perimeter Hardware Specifications

• Memory 2 GB
• Disk space 2 GB
• vCPUs 2
• vNICs Up to 10
• Virtual Network Interface Card type (NIC) E1000

Thanks to Juniper’s software evaluation program we can download the Firefly Perimeter security solution for free and test it out for 60 days. In this tutorial we are going to connect Firefly Perimeter to GNS3 and create a simple lab to test connectivity between two vSRX instances. As GNS3 has built-in support for VirtualBox and Qemu/KVM they both can used as hypervisor.

Firefly Perimeter virtual machines can be download here. You have to use your Juniper account to proceed the download but a valid service contract is not required to to download Firefly Perimeter virtual machine.

Picture 1 - Juniper Login Window

Notice that they Continue reading

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Big Switch Networks Launches Mature Hardware-Centric Data Centre SDN Solution

Big Switch Networks (BSN) launches Version 4.0 of Big Cloud Fabric for hardware-centric SDN data centre fabric. The Data Centre Fabric solution clearly shows the maturity gained from 5 years of shipping products while adding innovation in switch hardware through Switch Light operating system. At the same time, they have completed the transition from platform to product. A product that really has what you need in a hardware-centric SDN platform and addresses nearly all of the issues the competitors have not addressed. And it is shipping now.

The post Big Switch Networks Launches Mature Hardware-Centric Data Centre SDN Solution appeared first on EtherealMind.

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I Can’t Drive 25G

The race to make things just a little bit faster in the networking world has heated up in recent weeks thanks to the formation of the 25Gig Ethernet Consortium.  Arista Networks, along with Mellanox, Google, Microsoft, and Broadcom, has decided that 40Gig Ethernet is too expensive for most data center applications.  Instead, they’re offering up an alternative in the 25Gig range.

This podcast with Greg Ferro (@EtherealMind) and Andrew Conry-Murray (@Interop_Andrew) does a great job of breaking down the technical details on the reasoning behind 25Gig Ethernet.  In short, the current 10Gig connection is made of four multiplexed 2.5Gig connections.  To get to 25Gig, all you need to do is over clock those connections a little.  That’s not unprecedented, as 40Gig Ethernet accomplishes this by over clocking them to 10Gig, albeit with different optics.  Aside from a technical merit badge, one has to ask themselves “Why?”

High Hopes

As always, money is the factor here.  The 25Gig Consortium is betting that you don’t like paying a lot of money for your 40Gig optics.  They want to offer an alternative that is faster than 10Gig but cheaper than the next standard step up.  By giving you a cheaper option Continue reading

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Six Phases of Network Evolution

Last month I was asked to speak about Next Generation Networks at Indonesian Network Operators Group (IDNOG) forum. Whenever I speak about this subject with my customers, I usually use top down approach: started by talking about the business drivers and requirements, NGN architecture, to high level and low level design, before going deep into details to each supporting technology.

This time I decided to take a different approach. Instead, I tried to demonstrate how to build a new SP network from bottom to up. The objective is to show how the network can be transitioned from the simple one that offers a single service, to the one that carry multiple services and become resilient Next Generation Networks. I don't know if the message was received by the attendees, but I run out my 30 minutes time so I continued that effort by conducting the webex session few weeks ago.


The presentation I made for that session inspires me to write down about the six phases of network evolution below. And the phase will end up with the one thing that has become hot topic these days: Software Defined Network (SDN).

Phase 1: It begins with connectivity
When we build Continue reading

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Kurdish ISPs enable growth of Iraqi Internet

The recent violence in Iraq and the government’s actions to block social media and other Internet services have put a spotlight on the Iraqi Internet. However, an overlooked but important dynamic in understanding the current Iraqi Internet is the central role Kurdish ISPs play in connecting the entire country to the global Internet.

In the past five years, the Internet of Iraq has gone from about 50 networks (routed prefixes) to over 600. And what is most noteworthy this that the growth has not occurred as a result of increased connectivity from the submarine cable landing at Al Faw, as would be expected in a typical environment. Instead the dominant players in the Iraqi wholesale market are two Kurdish ISPs that connect to the global Internet through Turkey and Iran: Newroz and IQ Networks.

Help from the Kurds

The Iraqi Kurdistan region contains four main cities: Erbil, Duhok, Zakho and Sulaymaniyah. Newroz covers the first three, while IQ Networks provides service in the last. However, it would be incorrect to simply classify these providers as city-level retail ISPs. They also carry significant amounts of traffic for the rest of the country.

From the relative peace and stability of Continue reading

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Listo! Medellin, Colombia: CloudFlare’s 28th Data Center

With the World Cup at an end, so too is our latest round of data center expansion. Following deployments in Madrid, Milan and São Paulo, we are thrilled to announce our 28th data center in Medellin, Colombia. Most of Colombia’s 22 million Internet users are now mere milliseconds away from a CloudFlare data center.

A data center unlike the others

Our deployment in Medellin is launched in partnership with Internexa, operators of the largest terrestrial communications network (IP backbone) in Latin America. Internexa operates over 28,000 km of fibre crossing seven countries in the continent. Our partnership was formed over a shared vision to build a better Internet—in this case, by localizing access to content within the region. Today, it is estimated that as much as 80% of content accessed in Latin America comes from overseas. It is with great pride that, as of now, all 2 million sites using CloudFlare are available locally over Internexa’s IP backbone. Let’s just say we’ve taken a bite out of this percentage (and latency)!

If your Internet service provider (ISP) is not connected to Internexa, Continue reading

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More fun with #TSA

That's Julian in the center waving at me to stop taking pictures. That's Michael faced away on his right

Coming back through JFK, my bag was stopped in the x-ray. The examiner shouted "bag checked", and sat and waited. And waited. Nobody came. Finally, he shunted it aside to the special bag check area. Where it sat, and sat.

There was as TSA agent standing around doing nothing, except flirting with a cute passenger standing right next to me bag. Finally, I pointed out that my bag needed to be checked, at which point he talked to the x-ray examiner, pulled it out, and checked it (I had a spray can of foot powder I bought because omg I wore my workout shoes that stink to the convention).

So, of course, I asked to see his badge, which was turned away from me, and to talk to his manager. He refused to even tell me his name, but he did get the supervisor, who confirmed his name was "Michael Vails". The manager was quite rude, looking at me in disbelief as I pointed out the guy was standing around flirting with girls instead of checking my bag. He wouldn't let Continue reading

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Show 197 – Cisco Nexus Updates with Ron Fuller – Sponsored

Repeat guest and friend of the Packet Pushers Ron Fuller chats with Greg Ferro and Ethan Banks about the latest updates to both the hardware and software in the ever-growing and capable Cisco Nexus product line. We get a thorough update in this show, hitting lots and lots of highlights. Discussion What’s new with the […]

Author information

The post Show 197 – Cisco Nexus Updates with Ron Fuller – Sponsored appeared first on Packet Pushers Podcast and was written by Ethan Banks.