How does the internet work - We know what is networking
DoS – Denial of Service attack The concept behind the design of DoS attack is interfering in the normal functions of a server, web site, or other resources of a network. The hackers and even the virus writers can use number of ways in order to get this job done. One of the most common […]
Recently I was faced with an issue outside my normal expertise… those of you that know me realize I am anything but a security engineer. But in reality, you must always expand your horizons. One of the projects I’m working on involves migrating between two edge networks. Obviously, for a time there has to be traffic using both networks while you migrate services from one network to the other. This creates an issue from services that may be NAT’d from the inside of the network, where as the current (read: old) default route takes them out a different connection..
In order to solve this, you need to either change the default route, which may not be possible, or start NAT’ing the source address of your traffic. It took me a bit of time to get the details worked out, so I wanted to share what I found out.
Since 8.3, NAT has changed quite a bit. The most obvious change is the use of Object groups pretty much everywhere. In some ways, this simplifies the config. In others, not so much. Basic static NAT takes the form of a single object group that defines the Continue reading
I decomissioned my CustoMac to return it to its origins as a gaming rig. This was mainly due to the fact that trying to keep my MacBook and CustoMac in sync was turing out to be very labour intensive... This means I am using my Macbook Air as my main office PC but its limited I/O was proving to be a little bit of a problem!
I decomissioned my CustoMac to return it to its origins as a gaming rig. This was mainly due to the fact that trying to keep my MacBook and CustoMac in sync was turing out to be very labour intensive... This means I am using my Macbook Air as my main office PC but its limited I/O was proving to be a little bit of a problem!
I needed:
While the new range of Thunderbolt docks will be available later this year from the likes of Belkin and Matrox they will be priced in the £200-300GBP range (Expansys have the Belkin dock listed at £279). While it offers all the I/O I want over a high bandwidth connection I don't think I can justify spending over 1/4 the cost of the laptop itself on one... so I came up with a homebrew solution for under Continue reading
I decomissioned my CustoMac to return it to its origins as a gaming rig. This was mainly due to the fact that trying to keep my MacBook and CustoMac in sync was turing out to be very labour intensive... This means I am using my Macbook Air as my main office PC but its limited I/O was proving to be a little bit of a problem!
A colleague of mine pointed something out the other day: the numbers and letters that make up the Nexus 2000 (FEX) model actually have meaning! No, I haven't been living under a rock. I think it's pretty clear that with a model number like “2248TP-E” the “22” indicates this is the 2200 series FEX and the “48” indicates it's got 48 ports. But what about the letters that follow the numbers?
I will be giving a updated version of my bufferbloat talk there on Saturday, October 6. The meeting is about community wireless networks (many of which are mesh wireless networks) on which bufferbloat is a particular issue. It is in Barcelona, Spain, October 4-7.
We tried (and failed) to make ad-hoc mesh networking work when I was at OLPC, and I now know that one of the reasons we were failed was bufferbloat.
I’ll also be giving a talk at the UKNOF (UK Network Operator’s Forum) in London on October 9, but that is now full and there is no space for new registrants.
As I've written about in the past (here), Apple's AirPlay technology relies on Bonjour which is Apple's implementation of “zero config” networking. One of the things that Bonjour enables is the automatic discovery of services on the network. For example, an Apple TV might advertise itself as being able to receive AirPlay streams. An iPad that is looking for AirPlay receivers would use Bonjour to discover the Apple TV and present it to the user as an AirPlay destination. Both the Apple TV and iPad do all this without any user intervention or configuration (hence the “zero config” part).
That's fine and dandy but what my earlier article focused on was how Bonjour broke down in a network where what I'll call the “server” and the “client” are not in the same Layer 2 domain/VLAN. This is because the service discovery aspect of Bonjour relies on link-local scope multicast. These packets will not cross Layer 3 boundaries in the network.
The very simple answer is when the local NTP master controller is synching to the IP address 127.127.7.1 instead of 127.127.1.1. Ok, I think I need to clarify few things. In a number of CCIE workbooks, you’ll get a task to configure NTP access-control on the master NTP router to only peer with R1. After trying for a long time, you lookup the solution guide and realize that you were missing an ACL entry for the local address 127.127.7.1. Or you finished the task, everything works, you check the solution guide and ask yourself “why did they have an ACL for the IP address 127.127.7.1? I did it without it and it worked.”
This is something that I found to be very frustrating and without any information on the web. After doing some of my own research, it appears Cisco made few changes that are not very clearly documented.
To give you an example, R4 is the NTP master and R6 (150.1.6.6) is the NTP peer.
R4#sh run | i ntp | access-list
ntp master 4
ntp access-group peer 1
access-list 1 permit 150.1. Continue reading