BARC 2018

$\textbf{VPN}$ Works at which layer?


1. Application layer
2. Transport layer
3. Network layer
4. Data-link layer
> 
> **$\underline{\textit{Application layer VPN's}}$**
> 
> 
> This type of VPN will work with specific applications. The most common example of this type of VPN network is seen over the SSL connections that people use to purchase items online every day. The Application layer VPN provides encrypted communication between the web browser that the visitor is using to view the item and the server that is used to process the order. There are other applications that can be protected in this way, as well. This type of VPN security requires that each different application be supported.
> 
> 
> **$\underline{\textit{Network layer VPN's}}$**
> 
> 
> A $\textit{Network layer}$ VPN functions on layer 3. Unlike Application layer VPN security, Network layer VPN security will encrypt any traffic, regardless of the different applications being used. This type of VPN is used by some of the most well-known names in Internet security. For example, Cisco uses this layer for VPNs. These VPN servers are sometimes provided under the names L2TP and GRE.
> 
> 
> **$\underline{\textit{Data Link VPN's}}$**
> 
> 
> **$\textit{Data Link VPN}$** is used when two private networks need to communicate. It is one of the most expensive types of VPN connection. Normally, the protocol used over these connections does not provide encryption, so encryption needs to be added to the connection.
> 
> 
>
VLANs, trunks and tagging are all related. As you probably know a VLAN defines a broadcast domain, trunks allows vlans to travel from switch to switch and taggings either use the InterSwitch Link (ISL) which is Cisco proprietary or the open standard 802.1q. So to put it a bit more simply a trunk permits different vlans which are tagged to traverse over the link.


A good article describing this is an [introduction to VLANs](http://archive.networknewz.com/networknewz-10-20030725IntroductiontoVLANs.html).


If you are dealing with Cisco switches [understanding knowledge of VTP](http://www.cisco.com/en/US/tech/tk389/tk689/technologies_tech_note09186a0080094c52.shtml) is also necessary.


To create a VLAN enter global configuration mode


config t  

vlan 10  

name Sales  

exit


Creates vlan 10 with the name Sales


To assign a port to this VLAN you would create an access port


e.g.


config t  

int fa0/1  

switchport access vlan 10  

switchport mode access  

exit


to assign a range of ports (0 to 5) to vlan 10  

int range fa 0/1 – 5  

switchport access vlan 10  

switchport mode access  

exit


To create a trunk link between two switches requires you set up a trunk port


on the interface


switchport mode trunk


You will need a layer 3 device such as a router or L3 switch (3750) to perform intervlan communications.


The propagation of VLANS from a master switch (VTP server) to client switches requires setting up a VTP domain if you do not want to create VLANS on each individual switch. Hello,  


Please find below the answer for your questions

 QinQ Mapping

 Principles

QinQ mapping maps VLAN tags in user packets to specified tags before the user packets are transmitted across the public network.

* Before sending local VLAN frames, a sub-interface replaces the tags in the local frames with external VLAN tags.
* Before receiving frames from external VLANs, a sub-interface replaces the tags in the external VLANs with local VLAN tags.

QinQ mapping allows a device to map a user VLAN tag to a carrier VLAN tag, shielding different user VLAN IDs in packets.

QinQ mapping is deployed on edge devices of a Metro Ethernet. It is applied in but not limited to the following scenarios:

* VLAN IDs deployed at new sites and old sites conflict, but new sites need to communicate with old sites.
* VLAN IDs planned by each site on the public network conflict. These sites do not need to communicate.
* VLAN IDs on both ends of the public network are asymmetric.

Currently, only 1 to 1 QinQ mapping is supported. When a QinQ mapping-enabled sub-interface receives a single-tagged packet, the sub-interface replaces the VLAN ID in the frame with a specified VLAN ID.

Figure 7-8 QinQ mapping  
![imgDownload?uuid=4402391882494f24bacff41](https://download.huawei.com/mdl/imgDownload?uuid=4402391882494f24bacff41f1955d182.png)  


As shown in [Figure 7-8](https://support.huawei.com/enterprise/en/doc/EDOC1100055122/fbe6cdac/qinq-mapping#fig_dc_vrp_qinq_feature_003501), 1 to 1 QinQ mapping is configured on Sub-interfaces 1 on Switch 2 and Switch 3. If PC1 wants to communicate with PC2:

1. PC1 sends a frame to Switch 1.
2. Upon receipt, Switch 1 adds VLAN ID 10 to the frame, and forwards the frame to Switch 2. After Sub-interface1 on Switch 2 receives the frame with VLAN ID 10, Sub-interface 1 on Switch 2 replaces VLAN ID 10 with carrier VLAN ID 50. Interface 2 on Switch 2 then sends the frame with carrier VLAN ID 50 to the Internet service provider (ISP) network.
3. The ISP network transparently transmits the frame.
4. After Sub-interface 1 on Switch 3 receives the tagged frame from Switch 2, Sub-interface 1 on Switch 3 replaces the carrier VLAN ID 50 with VLAN ID 30.

PC2 communicates with PC1 in a similar manner.

 Comparison Between QinQ Mapping and VLAN Mapping

[Table 7-3](https://support.huawei.com/enterprise/en/doc/EDOC1100055122/fbe6cdac/qinq-mapping#tab_dc_vrp_qinq_feature_003501) describes the comparison between QinQ mapping and VLAN mapping.

Table 7-3 Comparison between QinQ mapping and VLAN mapping



| Mapping Type | Similarity | Difference |
|  |  |  |
| 1 to 1 | An interface maps the tag of a received single-tagged frame to the specified tag. | * QinQ mapping
	+ Performed on a sub-interface
	+ Used for VPLS access
* VLAN mapping
	+ Performed on an interface
	+ Used on Layer 2 networks where VLAN frames are forwarded
 |

  


  


Thanks you have to forward the sip and rtp ports of the snom. (before the update this was done by a sip application layer gateway, but we had to remove this because it breaks security.)

[image]

[security announcement: mitigating nat slipstreaming - the ipfire blog](https://blog.ipfire.org/post/security-announcement-mitigating-nat-slipstreaming)

last autumn, we learned about … Hyper -V is the virtualisation software layer used to run VM’s and SCVMM is the central management server to manage multiple Hyper-V servers. Hello Nanda, Basically you need to include the network drivers and the storage drivers.

+ You can find the drivers from Manufacturer site where you can filter the Category and download –

Like this – <https://snipboard.io/bQt5ER.jpg> well, then, you might as well put extra jacks out there anyway. in either case, it should work fine as long as ap is on the same subnet (ip address range.) that's exactly what it is. the ports you use for hdd's and so on. the pcie lanes are shared between them so if you use the m.2 slot, you lose the ports that share the lanes. 

it's only 2 and you still have 4 more :)

love my aorus pro wifi btw. snazzy board that works well and looks good doing it a network socket is an entry into a network. it allows transmission of data from one computer to another. engineers create a socket, tell it how to find the other computer, and then tell it to send. to receive data, a socket is created, told which computer to listen to and wait for data to come pouring in.(source: wikipedia) Dear Jay Nelish


Your Question is incomplete


is the specific system is not on Network? its might be a problem discovered last year, that system ping but not share any data, or cannot access the system


you click on start menu and then click on run  

type serivces.msc  

and run the computer browser service, Remote Procedure call service, Server, and Client service


and your problem will resolved  

but actually this is because of virus change your antivirus program and scan your system wtih updated A/V just a note to say this is resolved.one thing i'd not realised was that a policy doesn't take effect until 'save...to firebox' is selected. (smh)anyway, the original engineer got back in contact and reckons that the original policy that should have been handling the traffic (the one in the screenshots above) had too many destination choices in it, such that the firebox got confused and couldn't find the match, then moved on to the rest of the policies until it got to the end (block-all).he reckons this is an issue with the version of the os our firewall is running but is fixed in the new version.what's handling the traffic now is a new policy that accepts smtp traffic on port 25 from our server to any-external address.thanks all for your responses.