Category: Networking

PNRP – The Peer Name Resolution Protocol is new protocol made by Microsoft which is one of the first technology that will change the way we think about naming resolution in computer networking and possibly be the next DNS – Domain Name System like technology. PNRP is the new DNS but there are so much differences between them that it deserves an article on this blog.

Just to remind, is few simple words, DNS is a technology that enables us to type the domain name in the browser and leaves to Domain Name System to translate the domain name to IP address of the server where the web page is published.

As we are stepping forward to IPv6 implementation in the whole world in next years, there are technologies and future services that will not function at their best using DNS. In this case Microsoft was one of the first to develop a new technology, decentralized technology that will rely on neighbor computer for the name resolution and completely rely on IPv6 addressing. The Per Name Resolution protocol was the answer.

In case of DNS, it depends on a hierarchical structure of naming, while PNRP depends on peer systems in order to resolve the computer system’s location. Mainly, PNRP is a referral system that operates lookups on the basis of data it is familiar with.

Here is a simple example, if you require to search Computer 1 and you are close to Computers 2 and 3, it is important for your system to know whether Computer 2 knows Computer 1 or not. If the response of Computer 2 is positive, only then a a link to Computer 1 is provided to you. If the reply is in negative, then the system asks Computer 3 whether it knows Computer 1 and the same method is used with Computer 2. If none of the computers knows Computer 1, then the request is sent to other computers close to the system till it successfully finds the one that is familiar with Computer 1.

There are number of ways in which PNRP is different from the DNS service:

If you work in networking sooner or later there will be a situation where someone will bring you a device that you must connect to your network that was used somewhere else before. That can be something like switch, Fiber channel switch, some security appliance, different controllers etc. In that case this device will often have a static IP address assigned and you will not know whish address that is. In that case you are unable to communicate with the device and if you are connecting it to your network he will have different IP from you subnet. That will make the device unreachable.

You need to find this unknown IP address in some way so you can connect to the device and then change the IP.

Session Announcement Protocol as an experimental protocol designed for the purpose of multicasting a session’s information. IETF issued it as RFC 2974. SDP (Session Description Protocol) is being used by SAP as real-time transport protocol’s session depiction arrangement. With SAP use, correspondent can transmit SDP descriptions from time to time to an acknowledged multicast address and also to port.

This is a movie based on a true story. Is the issue you will have sooner or later if you are into networking and managing devices? Perhaps you will manage to upgrade hundreds of devices before you will see this happening but maybe it will be one of the first devices in production environment to go down exactly when you don’t have time for this kind of problem. Better be ready and read next short story about how is possible in very short time to revive a dead device stuck without IOS Software on it.

If you have a corrupt or missing software image on Cisco device this is the thing you should do:

Reset to the factory default using Mode button if you have the Mode button, if your device is not having that button then simply reboot the device and hit break or Esc key to stop the booting process. In this example, again, based on my true story I will take an example with recovering one of standalone Cisco Aironet Wireless Access points. It’s basically the same with all IOS devices and some devices that do not have IOS but some older software and then you want them to upgrade to IOS. It’s for example the situation with one very old Cisco Aironet AP350 device. Let’s go…

Block Traffic among two VLAN’s but only in one way, how to do that?

VLAN and VLAN configurations are very useful in all kinds of different ways. This configuration will be useful sooner or later for all network administrators out there.

It was a big challenge to resolve this tricky communication security requirement. The problem actually does not seem like a big deal but when you try to make it work you see that it is.

The goal was to make unidirectional communication filter between two VLANs. The request was to allow VLAN 10 to access VLAN 20 but not the opposite. The computers from VLAN 10 needed to access resources in VLAN 20 normally but computers from VLAN 20 had to be prevented to access VLAN 10.