MLD Considered Harmful
Multicast Listener Discovery (MLD) protocol is well hidden deep in the bowels of IPv6 protocol stack and most of us tend to gloss over it when we discuss IPv6 neighbor discovery process… until MLD raises its ugly head to bite an unsuspecting network administrator.
The problems with MLD are not new (and I wrote exhaustively about them a while ago), but it’s always nice to see other people raise awareness of broken IPv6 features like Enno Rey and his security team did during the IPv6 Security Summit (part of Troopers 15 conference).
Read more ...How to Upgrade IOS on Cisco 4500X Switch
Original content from Roger's CCIE Blog Tracking the journey towards getting the ultimate Cisco Certification. The Routing & Switching Lab Exam
The post describes the process of how to upgrade the IOS / Software on a Cisco 4500X switch. I will not be covering how to do a hitless upgrade using ISSU with 2 switches in a VSS pair. This process is performed on two switches which are not in production. So to perform the upgrade... [Read More]
Post taken from CCIE Blog
Original post How to Upgrade IOS on Cisco 4500X Switch
Understanding 802.11 Medium Contention
In this post, I dive deep into 802.11 medium contention to understand how it works as a precursor to the final blog post in this series where I’ll detail the two main sources of medium contention, identify Wi-Fi's breaking point (that'll be fun, stay tuned) and how this affects proper WLAN design in order to optimize wireless networks to prevent medium contention from killing your WLAN performance.
Read the full blog post over on the Aruba Networks Tech Blog...
This is the third blog post in a series about WLAN capacity planning. Be sure to read the first and second posts.
Cheers,
Andrew
OpenStack Neutron – The Dirty Network Detail
This post is just a quick response to a comment by Turing Machinæ on Show 227 – OpenStack Neutron Overview with Kyle Mestery, which was “I’ve learnt absolutely NOTHING about openstack from this podcast.” Whilst I don’t agree I have some empathy; time and time again I’ve found myself hitting a brick wall recently when […]
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The post OpenStack Neutron – The Dirty Network Detail appeared first on Packet Pushers Continue reading
Centec GoldenGate Chip to Challenge Broadcom Trident II
Centec enters the 10G age with its newest switch chip.
A Go Gotcha: When Closures and Goroutines Collide
Here's a small Go gotcha that it's easy to fall into when using goroutines and closures. Here's a simple program that prints out the numbers 0 to 9:
(You can play with this in the Go Playground here)
package main
import "fmt"
func main() {
for i := 0; i < 10; i++ {
fmt.Printf("%d ", i)
}
}
It's output is easy to predict:
0 1 2 3 4 5 6 7 8 9
If you decided that it would be nice to run those fmt.Printfs concurrently using goroutines you might be surprised by the result. Here's a version of the code that runs each fmt.Printf in its own goroutine and uses a sync.WaitGroup to wait for the goroutines to terminate.
package main
import (
"fmt"
"runtime"
"sync"
)
func main() {
runtime.GOMAXPROCS(runtime.NumCPU())
var wg sync.WaitGroup
for i := 0; i < 10; i++ {
wg.Add(1)
go func() {
fmt.Printf("%d ", i)
wg.Done()
}()
}
wg.Wait()
}
(This code is in the Go Playground here). If you're thinking concurrently then you'll likely predict that the output will be the numbers 0 to 9 in some Continue reading
The Facts Behind the Myth
I hate getting into lengthy discussions regarding open networking (or bare-metal) pricing as there are benefits other than price. However, with so many people trying to understand the industry transition, I feel compelled to jump in when I see confusing information.
Forrester analyst Andre Kindness recently published a report called The Myth of White-Box Network Switches which is causing a pretty interesting debate. The discourse forms, as Andre puts it, “I think there is misunderstanding/reading my research. I’m not saying one solution is cheaper. It highlights the cost”; however, the title of the report necessarily creates bias. Luckily, we had a chance to speak with Andre to better understand his perspective and intentions as well as relay our observations.
For the hardcore, we’ve gone through some of the market basics in prior blog posts; most notably Democratizing Capacity and Death of the Multipler Effect. Some of the absolute numbers in those analyses have changed; however, these hold true and directly relate to both the points that Andre was trying to make as well as the gaps in his analysis.
Bill of Materials Cost
The report makes two observations that we completely agree with. One is that, most of Continue reading