Difference between defining static routes with next-hop address or exit interface

How does the internet work - We know what is networking

There were a bit of confusion in my head about this case. It was not clear to me what is the difference between setting the static route using next hop interface IP address or using exit interface syntax. It seems that both methods are the same and that you have basically two different ways to […]

Difference between defining static routes with next-hop address or exit interface

Why ‘your’ project was outsourced

It’s easy to get upset when that cool new project you wanted is outsourced to an external VAR. The conversation usually goes something like, “You know the existing network and services really well so we’re  going keep focused there. We’re going to engage ACME systems integrators for ‘project awesome’ and get them to give that […]

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John Harrington

John is an experienced data center engineer with a background in mobile telecoms. He works as a network test engineer for a large cloud service provider, and is gradually accepting that he's a nerd. He blogs about network technology and careers at theNetworkSherpa.com. You can reach him on twitter at: @networksherpa

The post Why ‘your’ project was outsourced appeared first on Packet Pushers Podcast and was written by John Harrington.

Quiz #18 &#8211 Cisco vs. Juniper – Filtering ICMP between BGP Peers

Your company uses multi-vendor routing platforms (Cisco and Juniper) and has multiple sites connected via MPLS from a service provider. Each remote site has a GRE tunnel with the Headquarter (HQ) and a BGP session over this tunnel. After some security change in the network, sites that are Juniper-based behave differently than the Cisco-based ones, creating outage for the customer. What's wrong?

Cisco Nexus 7000 Proxy Routing


In my previous blog - Data Center Design Constraints, I mentioned some of the design caveats involving M and F series line cards in the same VDC or 7K chassis. In this blog, I'll talk about design considerations with classical ethernet on a 7K. For a deep dive, refer Design Considerations for Classical Ethernet Integration if the Cisco Nexus 7000 M1 and F1 Modules.

What prompted me to write this blog was a design whiteboard session with a customer to order the right line cards for the 7K switch. We know the F1 series line cards are strictly for Layer 2 functionality only. They do not perform Layer 3 routing functions, they cannot. The M series line cards perform Layer 3 routing. Consider a Nexus 7009 switch populated with F1 and M1 series line cards. Say servers A and B connect to the 7K. Server A and B belong to VLANs A and B respectively. If Server A needs to talk to Server B, the switch requires inter VLAN routing to route between VLANs A and B. Without the M series, or a separate router on a stick device, this is not possible, right?

If this were a Catalyst Continue reading

Balancing Complexity and Simplicity

I’ve been in tech for several years. Over time, I’ve configured things that I’m proud of and I’ve built things that I’m not so proud of. Most of the things that I’m less proud of involve unnecessary or unwarranted complexity that has created operational challenges. In some cases this was a result of a small […]

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Paul Stewart

Paul is a Network and Security Engineer, Trainer and Blogger who enjoys understanding how things really work. With nearly 15 years of experience in the technology industry, Paul has helped many organizations build, maintain and secure their networks and systems. Paul also writes technical content at PacketU.

The post Balancing Complexity and Simplicity appeared first on Packet Pushers Podcast and was written by Paul Stewart.

Show 159 – Finding a Way To Test It

A welcome return to the Packet Pushers of old where we get where we get a bunch of engineers around the table to generally poke sticks into a box of networking problems and laugh at the noises. Topics What VMware do with networking at VMworld Mentoring in the Day Job – how and what you do to […]

Author information

Greg Ferro

Greg Ferro is a Network Engineer/Architect, mostly focussed on Data Centre, Security Infrastructure, and recently Virtualization. He has over 20 years in IT, in wide range of employers working as a freelance consultant including Finance, Service Providers and Online Companies. He is CCIE#6920 and has a few ideas about the world, but not enough to really count.

He is a host on the Packet Pushers Podcast, blogger at EtherealMind.com and on Twitter @etherealmind and Google Plus.

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The post Show 159 – Finding a Way To Test It appeared first on Packet Pushers Podcast and was written by Greg Ferro.

Let Me Tell You…

In the last post in this series, I spent some time talking about the process of detecting a link failure (given down detection is always the more important issue in fast convergence); let’s continue by looking at notification. If a router discovers a down link, or a down neighbor, how does it tell all the […]

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Russ White

Russ White
Principle Engineer at Ericsson

Russ White is a Network Architect who's scribbled a basket of books, penned a plethora of patents, written a raft of RFCs, taught a trencher of classes, and done a lot of other stuff you either already know about, or don't really care about. You want numbers and letters? Okay: CCIE 2635, CCDE 2007:001, CCAr, BSIT, MSIT (Network Design & Architecture, Capella University), MACM (Biblical Literature, Shepherds Theological Seminary). Russ is a Principal Engineer in the IPOS Team at Ericsson, where he works on lots of different stuff, serves on the Routing Area Directorate at the IETF, and is a cochair of the Internet Society Advisory Council. Russ will be speaking in November at the Ericsson Technology Day. he recently published The Art of Network Architecture, is currently working on a new book in the area Continue reading

DCI with LISP for Cold Migrations

Let’s step back for a minute. So far in this series of blog posts on DCI, I’ve been focusing on extending the Layer 2 domain between data centers with the goal of supporting hot migrations — ie, moving a virtual machine between sites while it’s online and servicing users.

Is that the only objective with DCI?

Well if it was, there wouldn’t be a need for this blog post :-) Cold migrations have valid use cases too. Cold migrations occur when the virtual machine is shut down in one site and then booted in a new site. As part of that operation, typically an orchestration layer (such as VMware’s Site Recovery Manager) will poke and prod the VM to make it ready for operation in the new site. Most notably, it takes care of changing the VM’s IP address and default gateway.

Cold migrations do not have a requirement for the same IP subnet in both sites. This is because there’s no need to maintain active user sessions during the migration. Different IP subnets in the sites means no stretched Layer 2 which means no risk of combining failure domains!

What if that orchestration layer didn’t have to poke Continue reading

Healthy Paranoia Show 16: BSides DC Oktoberfest!

Willkommen, bienvenue, welcome!  Meine Damen und Herren, Mesdames et Messieurs, Ladies and Gentlemen. Introducing the latest installment in that grand epic known as Healthy Paranoia. Where the nerds are a little nerdier, and the evil bit is always set on your packets. In this episode, we help launch the very first Security Oktoberfest, aka BSides DC. […]

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Mrs. Y

Snarkitecht at Island of Misfit Toys

Mrs. Y is a recovering Unix engineer working in network security. Also the host of Healthy Paranoia and official nerd hunter. She likes long walks in hubsites, traveling to security conferences and spending time in the Bat Cave. Sincerely believes that every problem can be solved with a "for" loop. When not blogging or podcasting, can be found using up her 15 minutes in the Twittersphere or Google+ as @MrsYisWhy.
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The post Healthy Paranoia Show 16: BSides DC Oktoberfest! appeared first on Packet Pushers Podcast and was written by Mrs. Y.

Understanding OTV


I took notes while reading up on OTV documentation. If you don't want to read through the OTV IETF or related Cisco documentation, this can be a quick deep dive into what OTV is and how it functions. Hopefully I'll implement this in a real network sometime soon to share actual configs. 

Overlay Transport Virtualization (OTV)

OTV is a data center interconnect technology that routes mac based information by encapsulating mac addresses with IP addresses in an overlay transit network. As long as there is IP connectivity between two or more sites (DCs), OTV will function (ofcourse with the right hardware and configuration).

'MAC in IP' technique for supporting L2 VPNs over L2/L3 infrastructure. 
Routing and forwarding states are maintained at the network edge devices between sites, not within the site or core.
There is no need to extend STP across sites, and STP topologies can be local to each site.

Hardware Requirements:

As of March 2013, from here.

Cisco Nexus 7000
M1/M2 line cards
NX-OS 5.0(3) or later, 5.2(3) or 6.2(2) are Cisco recommendations
Transport Services License

Cisco ASR 1000
IOS XE 3.5 or later
Adv IP Srvcs / Adv Ent Srvcs license

The Only Two Ok Responses to Valid Feedback

Earlier this week, I wrote over on the Plexxi blog that the most important thing to look for in a potential new hire is coachability. If being coachable is the most important contributor to sustained long-term growth in employees, then how do you make yourself more coachable? There are countless tips and tricks to being […]

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Michael Bushong

The post The Only Two Ok Responses to Valid Feedback appeared first on Packet Pushers Podcast and was written by Michael Bushong.

Show 158 – Avaya – Software Defined Data Centre & Fabric Connect

We’ve done many podcasts now on Software Defined Whatever. Most of those shows are focused on diving deep into SDN technology and how protocols such as OpenFlow are meant to work. Let’s face it - this is fascinating stuff to a bunch of engineers. But over and beyond just being cool technology – SDN must solve a problem.

Author information

Greg Ferro

Greg Ferro is a Network Engineer/Architect, mostly focussed on Data Centre, Security Infrastructure, and recently Virtualization. He has over 20 years in IT, in wide range of employers working as a freelance consultant including Finance, Service Providers and Online Companies. He is CCIE#6920 and has a few ideas about the world, but not enough to really count.

He is a host on the Packet Pushers Podcast, blogger at EtherealMind.com and on Twitter @etherealmind and Google Plus.

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The post Show 158 – Avaya – Software Defined Data Centre & Fabric Connect appeared first on Packet Pushers Podcast and was written by Greg Ferro.

To Sit or Stand?

Unless you’ve been living under a rock for the last couple of years, I’m sure you’ve read the articles about how bad prolonged sitting is for your health. If you sit for a major part of your day (at work, in traffic and at home), your risk of diabetes and heart disease is doubled. The […]

Author information

Mrs. Y

Snarkitecht at Island of Misfit Toys

Mrs. Y is a recovering Unix engineer working in network security. Also the host of Healthy Paranoia and official nerd hunter. She likes long walks in hubsites, traveling to security conferences and spending time in the Bat Cave. Sincerely believes that every problem can be solved with a "for" loop. When not blogging or podcasting, can be found using up her 15 minutes in the Twittersphere or Google+ as @MrsYisWhy.
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The post To Sit or Stand? appeared first on Packet Pushers Podcast and was written by Mrs. Y.

IPv6 Implementation beyond theory & How playing with RA messages may be issue-istic

How does the internet work - We know what is networking

Some of this things I read in books and some of them took me few days of troubleshooting and sweating to get to them so I give them for free here to save you fellow networker some time: SLAAC The mighty SLAAC is the prefered method of IPv6 allocation, but is it so mighty? Or it […]

IPv6 Implementation beyond theory & How playing with RA messages may be issue-istic

Networking Field Day 6

I’ll be attending Networking Field Day 6 in San Jose, CA from September 11 - 13th. I am both honored and humbled to be a part of this event, and I am counting the days until my flight leaves for Silicon Valley. I love the area in general, as I’ve been there several times now - but having the privilege to go back for something like Networking Field Day is truly exciting.

Networking Field Day 6

I’ll be attending Networking Field Day 6 in San Jose, CA from September 11 - 13th. I am both honored and humbled to be a part of this event, and I am counting the days until my flight leaves for Silicon Valley. I love the area in general, as I’ve been there several times now - but having the privilege to go back for something like Networking Field Day is truly exciting.

RSVP Per Flow Limit and RSVP Call Rate

When configuring RSVP, the “ip rsvp bandwidth (bandwidth) [per flow limit]” command there is an optional parameter which limits the per flow bandwidth of individual RSVP reservation.  When using Call Admission Control for VoIP, that is the rate of an individual voice call in one direction, but the behavior is not as clear cut as it seems.

This feature was added to prevent other application from reserving all of interface’s reservable bandwidth.  If a video application uses RSVP within the network, it can take up majority of the reservation with a single video call.  For example if the smallest interface only has 500 kbps RSVP bandwidth and a video conference request all 500 kbps, no voice calls will be allowed through. Per flow limit wouldn’t allow one reservation to request all of the bandwidth. There are other methods to limit other application’s ability to reserve bandwidth with a more granular method using a RSVP local policy.

The actual VoIP rate is depended on many factors such as codec, sampling rate and header overhead.[1] The most common codec is either G.711 or G.729. For the G.711 codec, the IP rate is 80 Continue reading

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