Anycast HSRP and Design Considerations

hsrp

HSRP is the first hop redundancy Cisco property protocol which allows a transparent failover of the first-hop gateway. Many … [Read more...]

When Good NICs Do Bad Things: A Blast of IPv6 Multicast Listener Discovery Queries

This is the write-up of a recent event we experienced on our network.  This will be combination of a  journal of symptoms, … [Read more...]

Cisco Internal VLAN Usage

cgaller_blog_internalvlan1

About a month ago I worked on an old CatOS switch. Working on this switch reminded me about some of the differences between … [Read more...]

Out with the old, in with the new

blog_carl_niger

A few weeks ago I was asked to help a client turn up and move everything over to a new network. I have done this many times … [Read more...]

Kicking tires on Cumulus Linux

CL-whitebox-switch

So, I ended my last blog post with a wish - "hopefully someday I can get a real switch running Cumulus to play with ;-)" … [Read more...]

Fast Reroute Mechanisms

FRR

Network reliability is an important measure for deployability of sensitive applications. When a link, node or SRLG failure … [Read more...]

Switching to Linux for… Switches?

Lab whiteboard drawing

Like many folks out there, I'm following the rise of "whitebox switching", and am interested to see if (and where) it takes … [Read more...]

Don’t Need No Stinking Underlays

Why's everyone complaining about overlays; it's the underlays that are the problem. I've been in this awful game for … [Read more...]

Speaker for the Dead – Spanning Tree Protocol

dialog-warning

A friend of mine* text me early last week asking if I wanted to go to the cinema and watch the film After Earth. I … [Read more...]

Fun With Unmanaged Switches + Port Security

Figure 2: Connectivity After

I've just passed a year of my job working at a smallish non-profit, and one part that I really am enjoying is passing on … [Read more...]

Cisco OTV Implementation & Troubleshooting (Legacy Multicast mode)

For the details on what Overlay Transport Virtualization (OTV) is and how it works on a high-level, see my previous blog … [Read more...]

Cisco Nexus – Port “Inactive” Status

Quick notes on the "inactive" port status seen on the Cisco Nexus platform, which was perplexing the first time I ran into … [Read more...]

My First Junos Switch: Detailed Review After Three Days Under The Covers

Background This post is the story of my first practical look at Junos on Juniper EX-series switches. One day last … [Read more...]

Benefits & Limitations of SPAN Ports

A mirror or SPAN (switch port analyzer) port can be a very useful resource if used in the correct way. SPAN ports are … [Read more...]

OpenFlow Switching Performance: Not All TCAM Is Created Equal

The fundamental promise of OpenFlow - that any switches and any controllers can be used to build a network - was perhaps … [Read more...]