AS-Path Filtering

Before we get into the how, let’s talk about the why. According to the CIDR Report, the global IPv4 routing table sits at about 525,000 routes, it has doubled in size since mid 2008 and continues to press upwards at an accelerated rate. This momentum, which in my estimate started around 2006, will most likely never slow down. As network engineers, what are we to do? Sure, memory is as plentiful as we could ask for, but what of TCAM? On certain platforms, like the 7600/6500 on the Sup720 and even some of the ASR1ks we have already surpassed the limits of what they can handle (~512k routes in the FIB). While it is possible to increase the TCAM available for routing information, there are other solutions that don’t include replacing hardware just yet.

As far as I know, adjusting TCAM partitioning on the ASR1000 is not possible at this time.

Before I get too deep into this, I should clarify as many of you (yes, I’m looking at you Fry) are asking yourselves why is an ISP running BGP on a 6500… Many of my customers are small ISPs or data centers that have little to no Continue reading

Why Network Automation Won’t Kill Your Job

I’ve been focusing lately on shortening the gap between traditional automation teams and network engineering. This week I was fortunate enough to attend the DevOps 4 Networks event, and though I’d like to save most of my thoughts for a post dedicated to the event, I will say I was super pleased to spend the time with the legends of this industry. There are a lot of bright people looking at this space right now, and I am really enjoying the community that is emerging.

I’ve heard plenty of excuses for NOT automating network tasks. These range from “the network is too crucial, automation too risky” to “automating the network means I, as a network engineer, will be put out of a job”.

To address the former, check out Ivan Pepelnjak’s podcast with Jeremy Schulman of Schprokits, where they discuss blast radius (regarding network automation).

I’d like to talk about that second excuse for a little bit, because I think there’s an important point to consider.

A Recent Example

A few years back, I was working for a small reseller helping small companies consolidate their old physical servers into a cheap cluster of virtual hosts. For every sizing discussion that Continue reading

When they throw a Cisco guy to do something with HP networking gear

How does the internet work - We know what is networking

…There’s a nice little pdf to get you through HP is aware that most of networking engineers start their learning process in Cisco Networking Academy. Is is a normal course of events if you want to learn networking. Cisco has the very best study materials and best, carefully developed syllabus that is both high quality […]

When they throw a Cisco guy to do something with HP networking gear

Certified Application to Network Isomorphism Engineer, anyone?

There has been a recurrent debate over the last few years on the future of CCIEs, or more broadly network engineers as we know (and love) them today. While certainly calls for the “death of the CCIE” are certain to grab eyeballs, as always the more probably truth is more nuanced and tricky to predict. Certainly change is coming, but it is important to understand the true value of the present network engineer and how that maps into the future we expect.

Why would network engineers die?

Apart from a deadly virus outbreak transmitted by TCPDump, or for the true preppers out there – the distant alien race whose network engineers have all died out and who are coming to claim ours – the vast disappearance of all network engineers is most likely hyperbole. Yet it is probably fair to say that specific skills that network engineers have long used to compare or present their own value, attributes like the CCIE certification, are diminishing in the value they present to the market. The reason is pretty simple – while a CCIE (or JNCIE, etc) certification implies a thorough knowledge of overall network engineering theories and concepts and a detailed understanding Continue reading

Networking Is Not as Special as We Think It Is

I was listening to the Packet Pushers show #203 – an interesting high-level discussion of policies (if you happen to be interested in those things) – and unavoidably someone had to mention how the networking is all broken because different devices implement the same functionality in different ways and use different CLI/API syntax.

Some POODLE notes

Heartbleed and Shellshock allowed hacks against servers (meaning websites and such). POODLE allows hacking clients (your webbrowser and such). If Hearbleed/Shellshock merited a 10, then this attack is only around a 5.

It requires MitM (man-in-the-middle) to exploit. In other words, the hacker needs to be able to to tap into the wires between you and the website you are browsing, which is difficult to do. This means you are probably safe from hackers at home, because hackers can't tap backbone links. But, since the NSA can tap into such links, it's probably easy for them. However, when using the local Starbucks or other unencrypted WiFi, you are in grave danger from this hack from hackers sitting the table next to you.

It requires, in almost all cases, JavaScript running in the browser. That's because the attacker needs to MitM thousands of nearly identical connections that can fail. There are possibly rare cases where such connections may happen (like automated control systems), but JavaScript is nearly a requirement. That means your Twitter app in your iPhone is likely safe, as the attacker can't run JavaScript in the app.

It doesn't hack computers, but crack encryption. It reveals previously encrypted data.

Continue reading

Why Network Automation Won’t Kill Your Job

SSLv3 Support Disabled By Default Due to POODLE Vulnerability

SSLv3 Vulnerability

For the last week we've been tracking rumors about a new vulnerability in SSL. This specific vulnerability, which was just announced, targets SSLv3. The vulnerability allows an attacker to add padding to a request in order to then calculate the plaintext of encryption using the SSLv3 protocol. Effectively, this allows an attacker to compromise the encryption when using the SSLv3 protocol. Full details have been published by Google in a paper which dubs the bug POODLE (PDF).

Generally, modern browsers will default to a more modern encryption protocol (e.g., TLSv1.2). However, it's possible for an attacker to simulate conditions in many browsers that will cause them to fall back to SSLv3. The risk from this vulnerability is that if an attacker could force a downgrade to SSLv3 then any traffic exchanged over an encrypted connection using that protocol could be intercepted and read.

In response, CloudFlare has disabled SSLv3 across our network by default for all customers. This will have an impact on some older browsers, resulting in an SSL connection error. The biggest impact is Internet Explorer 6 running on Windows XP or older. To quantify this, we've been tracking SSLv3 usage.

SSLv3 Continue reading

vPC order of operations

Cisco Nexus can be very temperamental or capricious (pick the one you prefer ) and the vPC technology is not an isolated case. There is a certain way to configure vPC and we will see that in that blogpost. The following topology will be used: Enabling the feature Obviously we need to activate the […]

Standards are a farce

Today (October 14) is "World Standards Day", celebrating the founding of the ISO, also known as the "International Standards Organization". It's a good time to point out that people are wrong about standards.

You are reading this blog post via "Internet standards". It's important to note that through it's early existence, the Internet was officially not a standard. Through the 1980s, the ISO was busy standardizing a competing set of internetworking standards.

What made the Internet different is that it's standards were de facto not de jure. In other words, the Internet standards body, the IETF, documented things that worked, not how they should work. Whenever somebody came up with a new protocol to replace an old one, and if people started using it, then the IETF would declare this as "something people are using". Protocols were documented so that others could interoperate with them if they wanted, but there was no claim that they should. Internet evolution in these times was driven by rogue individualism -- people rushed to invent new things with waiting for the standards body to catch up.

The ISO's approach was different. Instead of individualism, it was based on "design by committee", where committees were Continue reading

Network Dictionary – Invariant

I use the term "invariant" quite regularly when designing networks. It sounds fancy.

The post Network Dictionary – Invariant appeared first on EtherealMind.

Don’t Be Afraid of Changing Jobs

Some people are corporate survivors, sticking with one company for decades. Some people move around when it suits, while others would like to move, but are fearful of change. Here’s a few things I’ve learnt about adapting to new work environments. It’s not that scary.

Corporate Survivors

We’ve all seen the people who seem to survive in a corporate environment. They seem to know everyone, and almost everything about the business. Return to a company after 10 years, and they’re still there. Somehow they survive, through mergers, acquisitions, and round after round of re-organisation. But often they seem to be doing more or less the same job for years, with little change.

Why Do People Stay?

There’s four possible reasons for staying at a job for a long time:

You’re really happy with what you do, and you’re well looked after.
You just don’t care. You come to work to eat your lunch and talk to your friends. You don’t care how you’re treated, or what work you do, as long as you get paid.
This is the only possible job you can get, due to location/skills/whatever.
You’re comfortable where you are, and you’re scared of moving, scared of what Continue reading

OpenStack and Cumulus Linux: Two Great Tastes that Taste Great Together

OpenStack is a very popular open source technology stack used to build private and public cloud computing platforms. It powers clouds for thousands of companies like Yahoo!, Dreamhost, Rackspace, eBay, and many more.

Why drives its popularity? Being open source, it puts cloud builders in charge of their own destiny, whether they choose to work with a partner, or deploy it themselves. Because it is Linux based, it is highly amenable to automation, whether you’re building out your network or are running it in production. At build time, it’s great for provisioning, installing and configuring the physical resources. In production, it’s just as effective, since provisioning tenants, users, VMs, virtual networks and storage is done via self-service Web interfaces or automatable APIs. Finally, it’s always been designed to run well on commodity servers, avoiding reliance on proprietary vendor features.

Cumulus Linux fits naturally into an OpenStack cloud, because it shares a similar design and philosophy. Built on open source, Cumulus Linux is Linux, allowing common management, monitoring and configuration on both servers and switches. The same automation and provisioning tools that you commonly use for OpenStack servers you can also use unmodified on Cumulus Linux switches, giving a single Continue reading

MindshaRE: Statically Extracting Malware C2s Using Capstone Engine

It’s been far too long since the last MindshaRE post, so I decided to share a technique I’ve been playing around with to pull C2 and other configuration information out of malware that does not store all of its configuration information in a set structure or in the resource section (for a nice set of publicly available decoders check out KevTheHermit’s RATDecoders repository on GitHub). Being able to statically extract this information becomes important in the event that the malware does not run properly in your sandbox, the C2s are down or you don’t have the time / sandbox bandwidth to manually run and extract the information from network indicators.

Intro

To find C2 info, one could always just extract all hostname-/IP-/URI-/URL-like elements via string regex matching, but it’s entirely possible to end up false positives or in some cases multiple hostname and URI combinations and potentially mismatch the information. In addition to that issue, there are known families of malware that will include benign or junk hostnames in their disassembly that may never get referenced or only referenced to make false phone-homes. Manually locating references and then disassembling using a disassembler (in my case, Capstone Engine) can help Continue reading

VMware Meets The Physical Network — What If?

With other acquisition rumors floating around, I figured I would add my own 2 cents and do some speculating.

It’s not uncommon to hear that VMware might acquire Cumulus. Like others, it’s one acquisition that I’ve speculated about for a while. There is already an interesting dynamic between Cisco and VMware, but as both companies continue to go to market with their Software Defined Networking (SDN), or controller based solutions, VMware still needs to run over a physical data center network. The physical network market is still largely dominated by Cisco though. Does VMware want or need to control the physical network?

Extending the SDDC

If VMware took their network strategy one step further and kept true to the Software Defined Data Center (SDDC), they would need a network operating system (NOS) that could run on approved hardware, e.g. hardware compatibility list (HCL). They need a bare metal (white box) switch company. Cumulus fits this build well because they are focused on creating open IP fabrics using tried and true protocols and already have their own HCL. They’ve also already partnered with VMware and support VXLAN termination on certain platforms. Continue reading

The Current State of SDN Protocols

The Current State of SDN Protocols

by Hariharan Ananthakrishnan, Distinguished Engineer - October 14, 2014

In last week’s blog post I started outlining the various standards needed to make SDN a reality. Here is more detail about the relevant protocols and the IETF’s progress on each one.

OpenFlow has emerged as a Layer 2 software defined networking (SDN) southbound protocol. Similarly, Path Computation Element Protocol (PCEP), BGP Link State Distribution (BGP-LS), and NetConf/YANG are becoming the de-facto SDN southbound protocols for Layer 3. The problem is that these protocols are stuck in various draft forms that are not interoperable, which limits the industry’s SDN progress.

Path Computation Element Protocol (PCEP)

PCEP is used for communicating Label Switched Paths (LSPs) between a Path Computation Client (PCC) and a Path Computation Element (PCE). PCEP has been in use since 2006. The stateful [draft-ietf-pce-stateful-pce] and PCE-initiated LSP [draft-ietf-pce-pce-initiated-lsp] extensions were added more recently and enable PCEP use for SDN deployments. The IETF drafts for both extensions have not yet advanced to “Proposed Standard” status after more than two years.

Because the drafts went through many significant revisions, vendors are struggling to keep up with the Continue reading

The Great Tech Reaving

#143116955 / gettyimages.com

It seems as though the entire tech world is splitting up. HP announced they are splitting the Personal Systems Group into HP, Inc and the rest of the Enterprise group in HP Enterprise. Symantec is forming Veritas into a separate company as it focuses on security and leaves the backup and storage pieces to the new group. IBM completed the sale of their x86 server business to Lenovo. There are calls for EMC and Cisco to split as well. It’s like the entire tech world is breaking up right before the prom.

Acquisition Fever

The Great Tech Reaving is a logical conclusion to the acquisition rush that has been going on throughout the industry for the past few years. Companies have been amassing smaller companies like trading cards. Some of the acquisitions have been strategic. Buying a company that focuses on a line of work similar to the one you are working on makes a lot of sense. For instance, EMC buying XtremIO to help bolster flash storage.

Other acquisitions look a bit strange. Cisco buying Flip Video. Yahoo buying Tumblr. There’s always talk around these left field mergers. Is the CEO Continue reading

Automatic protection for common web platforms

If you are a CloudFlare Pro or above customer you enjoy the protection of the CloudFlare WAF. If you use one of the common web platforms, such as WordPress, Drupal, Plone, WHMCS, or Joomla, then it's worth checking if the relevant CloudFlare WAF ruleset is enabled.

That's because CloudFlare pushes updates to these rules automatically when new vulnerabilities are found. If you enable the relevant ruleset for your technology then you'll be protected the moment new rules are published.

For example, here's a screenshot of the WAF Settings for a customer who uses WordPress (but doesn't use Joomla). If CloudFlare pushes rules to the WordPress set then they'll be protected automatically.

Enabling a ruleset is simple. Just click the ON/OFF button and make sure it's set to ON.

Here's a customer with the Drupal ruleset disabled. Clicking the ON/OFF button would enable that ruleset and provide protection from existing vulnerabilities and automatic protection if new rules are deployed.

For common problems we've rolled out protection across the board. For example, we rolled out Heartbleed protection and Shellshock automatically, but for technology-specific updates it's best to enable the appropriate ruleset in the WAF Settings.

Should you run OSPF over DMVPN?

Original content from Roger's CCIE Blog Tracking the journey towards getting the ultimate Cisco Certification. The Routing & Switching Lab Exam
You may have heard that you should not run OSPF over DMVPN but do you actually know why? There is actually no technical reason why you cannot run OSPF over DMVPN but it does not scale very well. So why is that? The reason is that OSPF is a link state protocol so each spoke […]

Other pages of interest:

Post taken from CCIE Blog

Original post Should you run OSPF over DMVPN?

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