For questions about the OSI layer-2 (data-link layer).
1
vote
1answer
25 views
Why do I see “ethernet” keyword in my wlan0? [on hold]
When I check my wireless network card interface with the command ifconfig wlan0:
ether -my-mac-adress- (Ethernet)
I just started to learn this stuff, but I thought Wifi and Ethernet are kind of ...
5
votes
4answers
947 views
Do layer 3 protocols use layer 2 protocols?
I saw the STP on layer 2. The guy that made the tutorial says at the end :
Even though it seems that Layer 2 access layer solutions are slowly
being replaced by blazing fast Layer 3 solutions.
...
3
votes
2answers
378 views
Spanning Tree on the interface that resides at end users
I do not understand why we use portfast and in fact STP on the interface of a switch that is directly connected to end users. Indeed, a user can interfere with the STP election and perform DDoS (that ...
3
votes
2answers
58 views
How the packet is routed between two host from same sub-net and associated with same AP?
Given host 'A' and 'B' have IP 10.10.0.5 and 10.10.0.8 respectively, the sub-net mask for both are 255.255.255.0, both 'A' and 'B' are associated and connected to the same AP, and the AP is connected ...
0
votes
1answer
40 views
Counting the Number of re-transmission for a single UDP packet transmission in IEEE 802.11?
I was working with a client-server project based on UDP and 802.11 as a link and physical layer. There, the client was trying to probe some packets in the wireless channel to gauge channel condition. ...
6
votes
2answers
357 views
How is the Groupwise Transient Key used in WiFi networks?
In Wifi WPA, I understand that during association, a 802.11 client and AP negotiate a Pairwise Transient Key (PTK), using which the Groupwise Transient Key(GTK) is provided to the station.
I ...
3
votes
2answers
63 views
Does WiFi broadcast traffic from a station go through the access point?
Let's say I've got two devices connected to my Access Point, a laptop and a tablet. If the laptop sends unicast traffic to the tablet, I understand that it must go through the AP.
However, how is ...
1
vote
1answer
35 views
How to understand the rectangle shape wave? [closed]
I am read a tutorial:
there is example, says the source signal waveform like this.
I can not understand this, because I did not laid eyes on the rectangle shape wave. who can explain to me?
0
votes
0answers
12 views
Is the analog signal or digital signal inside the twisted pair? [duplicate]
Is the analog signal or digital signal inside the twisted pair?
In our network, the twisted pair linked to Switch and Hosts.
I want to know the twisted pair's signal is analog signal or digital ...
2
votes
2answers
34 views
Can Multicasting be duplicated by broadcasting on a subnet?
Is there any functional difference between:
A) Broadcasting to a range of addresses
B) Putting the range of addresses into a subnet and broadcasting to that subnet
Would it matter if there was a ...
2
votes
1answer
39 views
Layer 2 error correction
How are acknowledgement sent at data link layer to the sender when crc of frame is incorrect?
0
votes
2answers
72 views
BGP with x2 sessions and x2 L3 VLANs - Please Explain
I am learning about Cisco BGP networking now and came across an interesting situation. In my examples, there was one which suggested that two VLANs were configured on Layer 3 in order to run two BGP ...
1
vote
1answer
46 views
Layer 3 switch model 3950 encapsulation
How to ensure trunk link in the switch are using dot1q encapsulation, when dtp (dynamic trunking protocol) is enable along with vtp.
I know when manually setting trunk links, you can force the trunk ...
1
vote
1answer
20 views
Protocol Identification
At the data link layer, many protocols run simultaneously, or one after other, right? my question is how date link layer knows about which layer 2 protocol to run and at which sublayer?
1
vote
3answers
78 views
Why do clients request a MAC via ARP, if the router knows the local LAN's MAC addresses already?
If I have an infrastructure type network, why does a local PC send out an ARP request for a MAC? Doesn't the router know the MAC addresses already, since it is using at least Layer 2?
Does it do ...
0
votes
3answers
60 views
Can Ethernet II frame's Type be Layer1's or Layer4's protocol?
The Ethernet II frame's Type field can be IPv4, ARP, so it can be Layer2 and Layer3's protocol.
This is a snapshot of frame captured by WireShark.
But I have a question, whether it can be other ...
2
votes
1answer
52 views
Connecting Layer 2 switchport to layer 3 port
I have a config that I am trying to bring up, and in my mind it should work, but perhaps I am missing something.
The idea is that one end of the link is a layer 3 interface on a router. The other end ...
0
votes
2answers
37 views
Layer 2 Routing between subnets and VLANS [closed]
I am studying for my Networking exam and from what I have pieced together from other posts on here is this. Please correct me if I'm wrong:
Layer 2 switches can only route packets between different ...
0
votes
1answer
28 views
Separate network for test systems
I often read that you should put customer machines into a separate (testing) network like a DMZ.
Is a layer 3 device (switch/router + firewall) a good option for this? Since some ports need to be ...
1
vote
0answers
54 views
Why is RTS/CTS optional for IEEE 802.11?
In wikipedia it is stated:
Request to Send (RTS) frame: The RTS and CTS frames provide an optional collision reduction scheme for access points with hidden stations. A station sends a RTS frame as ...
-1
votes
2answers
49 views
Slotted Aloha Protocol divides up time into slots, each slot corresponding to one frame. Is this same TDM?
Slotted Aloha Protocol divides up time into slots, each slot corresponding to one frame. Is this the same as Time Division Multiplexing (TDM)?
0
votes
0answers
22 views
Fibre Channel Forwarding between devices behind single NPIV port
How does Fibre Channel switch with NPIV enabled port operates, when two devices behind the single NPIV port want to communicate with each other?
e.g. Ethernet switch, would just drop frames, if ...
3
votes
5answers
387 views
Is there a Layer 2 address advertising protocol?
I needed help in understanding if LLDP/CDP is the Layer 2 equivalent to RIP or say any Layer 3 route advertising protocol. If not,is there a protocol that advertises the MAC Address Tables among ...
0
votes
1answer
85 views
Routing and Bridging on a Layer 2 or Layer 3 device
The thing that intrigues me is, say I have a router and I configure it’s interface as a Layer 2 and have 2 Vlans on the same router. So if I want to transfer the data from one Vlan(say VLAN-10) to ...
4
votes
1answer
576 views
Do we send ack frames in ethernet? if not then how does a router know if its neighbors are down or not?
So first off, do ethernet sends ack frames or not?
if it doesn't : then how does a router know whether its neighbors are down or not?
if it does : then is it cumulative ack with an ack timer or one ...
0
votes
1answer
49 views
Frame transfer from one switch to another configured with VLANS
Hi,
My question is related to the Vlan. And this question would consist of 2 parts.
1)Would Switch 1 know all the devices present in Vlan 2 or Vlan 3, including the ones present in the Switch 2.
...
0
votes
1answer
26 views
How to show all data (bitstream with preamble, SFD) on Ubuntu with an Intel Ethernet Interface?
On my PC I have an Intel Ethernet Connection I217-LM with e1000e driver.
If I receive packets in Wireshark or any libpcap based tool, the received ethernet frames start with Ethernet II frame and end ...
1
vote
1answer
68 views
Why are Frame Relay, ATM and MPLS called “Layer-2 VPN”?
A VPN results, when two physically separate networks become virtually one bigger network.
But Frame Relay, ATM and MPLS don't do that, they just connect two network, but they don't unify them.
So ...
3
votes
2answers
816 views
Does it make sense to map a VLAN to each LAN?
I saw a picture of a network-structure with VLANs in it:
Why would somebody structure their network like this? Does this even make sense? I mean, they are in a different LAN, why then mapping a VLAN ...
1
vote
1answer
155 views
Bridging networks without NAT: how it's done?
I have quite limited networking experience, so probably i'm asking about very simple things. I'm reading about linux bridge interfaces, and documentation states that there is no NAT by default and ...
0
votes
0answers
23 views
Bit Stuffing Complication (Data Link Layer)
In Bit Stuffing technique, where we add an extra bit in our frame, so that a particular sequence of bits in our actual data doesn't match the EFD (End of Frame Delimeter);
Consider: Data = 110001001, ...
5
votes
1answer
91 views
ETH II vs 802.2 LLC/SNAP
I have a project where there is a custom implemented layer 2 protocol. An engineer before me decided to use what I'm used to as the Ethertype field as a size field. For awhile this looked right ...
1
vote
2answers
74 views
1 Layer 3 Switch, 2 Vlans, 2 Subnets, and an Unmanaged Switch
Is it possible to for a device with the ip address 192.168.0.1 and Vlan 100 to communicate with an other device with the ip address 192.168.1.1 and Vlan 200 with the following architectures
Senario 1:...
3
votes
2answers
378 views
Is there 64k range VLAN support?
All i have learnt and understood so far about VLAN is - we can create a max of 4k VLANs (subjected to platform capability). However, as per the protocol 802.1Q there is only 12 bits kept for ...
2
votes
2answers
143 views
Routing steps on a serial port
"Because the exit interface is not an Ethernet network, R2 does not have to resolve the next-hop IPv4 address with a destination MAC address."
- this is routing from serial port , can anyone explain ...
1
vote
1answer
111 views
How would you map a network at layer 2 without CDP or LLDP?
I'm on an ASA right now and can path my directly connected next hop devices via IP address, but I want to make sure there isn't a switch in between.
Another related question, when I "show arp" it ...
0
votes
1answer
55 views
Advertise routes in simple switched network
I'm trying to build a fairly simple network.
I've got a few devices acting as the network core, which are basically all connected to each other by a simple Ethernet switch.
Each of these devices (I ...
4
votes
2answers
243 views
High availability LAN segment with Cisco ISR4451X and 2 x Netgear GS724 - Port-channel vs. BDI vs. BVI?
I have a customer that is getting a new 1Gbps ISP connection and wants his servers connected across two switches for redundancy and protection from:
failure of a router port
failure of a network ...
1
vote
2answers
110 views
CSMA/CD - CSMA/CA switch mix
Suppose I have 2 switches; one CSMA/CA (gigabit) and the other CSMA/CD (gigabit), would they work together when connected and if so would there be any dip in network performance?
Thanks in advance!
0
votes
1answer
75 views
How might I test layer2 latency over ethernet without a target IP address? [closed]
Is there a way, via standard ethernet layer2 protocols, to test latency to a device without using it's IP address?
Background:
I have a fibre "box" provided by my ISP physically connected to my ...
7
votes
7answers
3k views
How LAN works in video games if only one station is permitted to transmit?
I've read the in a LAN the data is transmitted in packets so as to allow only one station to transmit at a given time, so how could this be applied in video games LAN parties if only one device is ...
2
votes
2answers
240 views
What is the difference between CAM and FIB table?
As far I know,
CAM table is Content Addressable Memory table where MAC address is stored
FIB table is Forward Information Base table which is a dynamic table that maps MAC addresses to ports.
Both ...
0
votes
3answers
279 views
Cannot Ping Linux PC through L2 Switch
I’m a little embarrassed to be asking this but here goes.
In a training video for CCENT, I see a switch connected to 2 PCs that are pinging each other on the same subnet. I try to replicate the ...
3
votes
1answer
93 views
Does an ethernet checksum include padding bits?
For ethernet II (aka ethernet DIX) frames that are padded to contain 64 bytes total, is the checksum in the last 4 bytes computed with the padding bits as input?
1
vote
1answer
302 views
SD-WAN vs MPLS VPN
Citing wikipedia on MPLS VPN
There are three types of MPLS VPNs deployed in networks today: 1.
Point-to-point (Pseudowire) 2. Layer 2 (VPLS) 3. Layer 3 (VPRN)
I am confused about the difference ...
0
votes
0answers
72 views
type of architecture leaf spine
Please I would like to know, what is the difference between the two types of leaf spine architecture (layer 2 and layer 3) and, is it possible to have a topology with both types?
So the difference ...
0
votes
1answer
139 views
Layer 2 ARQ protocols
Some authors (i.e. Tanenbaum, Stallings) reference ARQ protocols as layer 2 mechanisms for handling errors.
Even this page from Wikipedia says that
these protocols reside in the Data Link or ...
4
votes
3answers
796 views
Error Detection across OSI layers confusion
Confusion:
How does the transmitter know that his information( bits in physical layer, frames in data link layer, packet in network layer ) was transmitted correctly to the receiver?
I know that in ...
3
votes
1answer
66 views
Example VLAN without any Router — Security Problems?
I was reading a VLAN setup walkthrough, and the author had an interesting idea for setting up VLANs without a router (which you don't normally see). At first glance, this doesn't seem like it actually ...
3
votes
1answer
77 views
VLAN Isolate Setup
How can I set up a switch so that devices on one switch port are isolated from devices on other switch ports? I'm guessing this should be done with VLANs, but I'm open to other options as well.
...
