Understanding the “NTP access-group” command in IOS.
NTP has always been one of those things I have found tricky to really lab up. Its fairly easy to setup, but verifying whether everything is working as you expect, can be hard because it takes a while to synchronize (and even unsynchronize).
First take on SDN
I have been very quiet when it comes to the topic of SDN (Software Defined Networking). However, these days you can hardly go through your day without spotting an article about it.
The reason I have been quiet is pretty simple.
The Tech Interview
Some very smart people have created a new website aimed at the career aspects of the tech world.
In time the site should prove to be a valuable tool for anyone trying to land a job in the tech industry.
MPLS VPN Per VRF Label feature
In this post i would like to explain the usage of the “MPLS VPN Per VRF Label” feature.
By default, in each VRF, prefixes are assigned a VPN label, used to identify the route within the VRF itself.
This label is the only label that is being looked at by the receiving PE router.
Going to DKNOG
I just ordered my ticket for DKNOG, which will be happening on March 21st in Copenhagen.
Catch me there if you can!
Cisco to sell Linksys to Belkin.
Yesterday it was announced that Belkin intends to purchase the Linksys division of Cisco’s hands.
I for one, am very happy to see this happen.
I think that for Cisco to be really great, it needs to focus on its core competencies, which does not include home networking equipment.
Some IOS-XR Training
Just wanted to let you know of a good place to go for some IOS-XR training.
Head on over to FryGuy’s place:
ASDM “Unconnected Sockets Not Implemented” Error
I ran into this error today on an old ASA and i needed a quick fix that didnt involve downgrading any Java versions from the clients servers.
I can confirm that by using version 6.1(5)51 of the ASDM works correctly (as noted in the link below).
Gold Nugget's, courtesy of Arista
I think the video below is worth going through for a couple of reasons.
First off, it explains one networking company’s strategy towards SDN (Software Defined Networking). Its a great academic concept with lots of potential. However there’s no real push for it from customers (at least the customer base of Arista).
The cat is out of the bag.
The cat is out of the bag.
I am going for my 2nd CCIE. This time its in the Service Provider track.
For a while i have felt something missing. And what is missing is a clear cut direction on what i want to learn more about in my professional life.
Week on the wire – Week 10.
I think one of the most important things this to happen this week, was a public announcement
from the boss of TeliaSonera.
He announced that they would in the near future, start to charge people for any VoIP calls they would make through their broadband services.
Update on INE's SP track.
There’s news on INE’s Service Provider material.
Updated workbooks for the SPv3 will be arriving “soon”. Hopefully that means within a month or two.
If you are interested, you can read more and even get a peak into a sample lab.
Week on the wire – Week 9.
Its been a rough week. I have been finishing up projects and getting rid of loose ends.
I have also been giving a couple of lectures on IPv6 (Basically primers) to customers as well as some information on basic failover configuration in IOS.
A picture which is worth far more than a 1000 words.
The picture below should be put into a frame and put onto the desk of everyone in the IT industry.
By day, I am a consultant, so I have quite a few stories that relate to this picture.
Obviously the picture shows that, at every step in a project there are misunderstandings.
CAR – The grand-old man in policing.
Below are my findings regarding CAR. Please be advised that this is work in progress.
CAR is the ancient way of doing policing.
It is not configured using any of the new and fancy MQC style configuration.
It is an interface-based command set.
Week on the wire – Week 7.
A couple of things i have found interesting this week.
The first one is that Intel is still in the game for making NIC’s. Even though they are doing some good ones in the server space, this batch seems to be targeted at the entry-level.
Cloud enabled task management.
I have been using Things as my task management program for about 5-6 months.
Its been better than not using anything at all, but what has really annoyed me quite heavily is its inability to do “Cloud” synchronization. The only form of synchronization from Things is through your wireless network.
Help the readers out!
I own alot of books.
By books, i mean those paper things, that takes up alot of space and for which we chop down trees.
Recently, i have been shifting my reading onto my iPad. Its easy to carry around, it holds multiple books and pdf files.
Great tips for making changes to your network
I stumbled across this blog post which i think most will find very interesting.
At least i think it contains some ideas that should be followed whenever you make a change to your own or your customers network.
Head on over and take a look: http://lamejournal.
Odd EIGRP behavior
Update: By most examinations, this seems to be a bug. A clever guy at the Cisco support forums might offer the reason why this happens. Thanks to everyone for clearing this up! (https://supportforums.cisco.com/message/3519430) I was trying someting out the other day concerning EIGRP when i ran into an issue i still cant explain, so i would like to put it out there for scrutiny.
In this post i will shed some light on some spanning-tree info that has been floating around. But also an explanation why i choose a non-obvious answer to an IPexpert question.
Specifically 2 things.
The first one is the selection of ports and what _exactly_ selects the root port.
Back from trip.
I am back from our company trip to Dubai.
Dubai is a fantastic place. Its my first time in the middle east and it left a great impression.
The whole city struck me as a proof-of-concept kind of city. They decided they wanted to do something great and they went ahead and did it.
Some thoughts on Openflow
It seems that everywhere i look, be it on twitter, google+ or my regular reading list of blogs, Openflow comes up alot.
What is Openflow?
Openflow is an initiative to create a protocol and an API infrastructure to improve overall functionality of your network.
Quick Tip: SPD
One of my friends told me about a feature called SPD and whether i knew about it. I didnt so i decided to read a bit more about it.
SPD stands for Selective Packet Discard. As the name implies it has something to do with discarding packets.
NAT shows its ugly face in the IPv6 world.
Lately theres been some fuzz in the corners about the need for NAT in the new world order of IPv6.
I think its a poor design choice and ill give my reason below.
One of the reasons why people seem to feel like they need NAT, is accessibility to IPv4 only content.
Thoughts on the SSL/TLS – Beast
It seems like every day, there are some vulnerability or crack announced on the geek news-outlets.
For some reason, the recent publication of an exploit of a flaw in the SSL/TLS implementation in some versions, made me extra curious and it made me think a little harder about this whole security business.
Flex Links, otherwise known as the devil for your L2 network.
In all fairness, lets actually figure out what this feature
is used for.
The most important thing you need to know is the fact that
Flex links disable your spanning-tree process.
Great free multicast lecture by INE
I just watched this great lecture from INE on multicast. Well worth sharing:
L2TPv3 – A wormhole through your L3 network.
Using L2 tunnel protocol version 3, you can accomplish what so many scientists are working on. A Wormhole!
Granted, this wormhole is just through your L3 network, so it might not raise as many eyebrows, but its still a nifty tool in your toolbox.
The Verify Source command.
In this small post i want to clarify the use of the “ip verify” command.
There has been some confusion on the usage of this command, especially in conjunction with the access-list parameter. I would like to clarify this here.
Time people.. Time…
Being a network consultant means getting access to lots of customers using a range of different equipment.
One thing thats common for almost all of them, is the fact that the time is not in sync throughout their devices. As you may know, this is a real issue when you are trying to sort out a problem.
In this article i will try and setup a very simple example using Cisco IOS IPS (Intrusion Prevention System).
As before, a simple topology consisting of 3 routers will suffice.
They are configured as follows:
Topology for IPS example. R1 will act as our source host.
Thoughts on the Skype / Microsoft deal.
My take on the Microsoft purchase of Skype.
Only last week i attended a mandatory briefing of Lync, Microsofts all-in-all wonder for communicating.
Basically its a PBX, IM-server, Video-conferencing, Outlook-Integrator kind of a product.
Basically they have taken alot of code from alot of different half-done products and thrown them into one big pile and put alot of marketing money behind it.
Over selling and underdoing.
Warning: The following is primarily a rant! You might not find it applicable in your situation, or you might simply not care. You have been warned 🙂
Having been a consultant for a while now, i am constantly amazed at how solutions are made up and what is sold simply because it has a buzz-word in its title or description.
Working through detailed blueprint.
I am going through the detailed blueprint, one item at a time and verifying that there are no surprises. Especially IP services and security is something i havent paid enough attention to in the past.
Anyways, there are lots of items on that darn list and going through them all takes alot of time.
Frame-relay compression and fragmentation.
Link optimization on frame-relay.
Using frame-relay, bandwidth is especially a concern.
It is possible to optimize this bandwidth in several ways.
I will concentrate this post about compression and fragmentation.
First off, with compression on frame-relay there several methods of accomplishing this.
Final Rack Photo
As promised, here is a couple of photos of the final layout.
More detailed view
Thats all there is to it 🙂
So I modified the previous layout a bit.
The concern i voiced about the 3640 was enough to make me figure out a way to have that one as the bottom piece of equipment.
This is what i ended up with:
I need to start cabling all of this gear into place. I have made a layout which i think i will try out.
The only thing that concerns me is the weight of the 3640 router. Its a heavy baby.
Beginning of March
I have received the rest of my routers (1841s), I have also received the memory and flash upgrades for them all (256meg memory and 64mb flash). The guy who sold them to me was very helpful and it turned out he had the cables that i needed as well (some Smart-serial to Smart-serial, as well as some DB60 ones).