Questions tagged [layer2]
For questions about the OSI layer-2 (data-link layer).
337
questions
0
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1answer
33 views
Does a router have multiple DLLs inside?
I came across a practice question of true/false answer type . The statement is:
"A router has single network layer that will interact with 2 Data link layers" .
Ans:True
(no explanation ...
0
votes
3answers
86 views
No internet access on VLAN
I'm trying to setup VLAN on my TL-SG3210 (3.0).
I created simple VLAN:
vlan 10
name "vlan10"
Then, I assigned port 2 & 3 to VLAN.
I also created interface:
interface vlan 10
ip ...
1
vote
0answers
42 views
What are non-learning and learning VLANs?
I was going through some IEEE standards for switches (IEEE 802.1aq and IEEE 802.1Qca), and came upon a terminology of learning and non-learning VLANs.
I read that learning VLANs are used in Shortest ...
0
votes
2answers
49 views
How do layer-2 devices (bridges/switches) join a multicast MAC address?
I was going through the IEEE 802.1Q (2018) standard on my own. The standard speaks about group addresses, and how these group addresses are learned by transit bridges, which is all fine.
But how do ...
1
vote
4answers
86 views
Do layer 2 protocols allow hosts to communicate without being on a network?
Please go easy on me as I'm just a noob in the networking space.
As far as I have learnt, layer 2 protocols use MAC addresses for communication, which doesn't really depend on what network you're in ...
0
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0answers
18 views
How is it possible that CSMA/CA works in areas with a lot of users within a small radius (e.g. rallies, concerts, etc.)?
My understanding of CSMA/CA is that devices listen until a Wi-Fi channel is idle before sending packets. If a collision still happens, then the devices waits a random interval before attempting to ...
0
votes
2answers
37 views
Is there a layer 2 protocol that can be used to send arbitrary data?
I would like to design several devices that receive simple commands from a single controller device all residing on the same layer 2 switch. Is there a protocol that allows me to do this without ...
0
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3answers
65 views
Is it possible to have a local area network with only layer 1 and not layer 2 of the OSI model?
I know the OSI model has seven layers. Can you consider a LAN to exist without layer 2 and just layer 1? The answers that I saw on Quora were not clear. Some of the answers on Quora came close to ...
1
vote
1answer
55 views
100BaseTX Ethernet Idle code (“/I/”) 4B/5B origin
While searching how the PHY LINK status is determined, I stumbled across this answer :
In 100BaseTX Ethernet, link pulses aren't used, but instead, link
status is detected and maintained via the ...
1
vote
2answers
42 views
Proxy-ARP when the destination device is connected to the same layer-2 switch, but belongs to a different subnet
I have recently learned about Proxy-ARP and am slightly confused about what would happen in the following scenario. Let's say I have two host devices A (IP: 10.0.0.10/24) and B (IP: 10.0.1.10/24) that ...
0
votes
1answer
25 views
Routing switches at core and distribution
My employer has your standard 3 layer architecture, however they want both core and distribution routing and switching.
This is so that some networks are routed, and some use only layer 2 between ...
0
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2answers
32 views
Tagging a Vlan across routers
I'm usually against tagging a VLAN across a router, as to not incur issues with spanning tree.
My company is asking the following
PLC --Vlan72-- SwitchA --RouterA---CoreRouter---RouterB---...
9
votes
3answers
2k views
Why does PPP need an underlying protocol?
The Point-to-Point Protocol is (at least according to Wikipedia) a Datalink Layer Protocol.
I know that different use cases exist for it but on examining the image below from Wikipedia one can see ...
1
vote
1answer
65 views
How does Network Layer behave when client received a unicast DHCP offer?
I went through various stack exchange post to understand the concept of DHCP offer when it comes as a unicast to client from the DHCP server.
A server can send a unicast DHCP offer since it knows the ...
3
votes
2answers
346 views
Capturing LACP PDUs in an aggregated link on Juniper MX
We need to capture LACP PDUs on a member link of an aggregated bundle link on Juniper MX connected with other router via DWDM link and save the output in .pcap format using write-file knob.
Can ...
6
votes
2answers
1k views
How do I know the switch is layer 2 or layer 3?
Is it possible to find the switch is Layer3 or Layer2 in (Switch)CLI? Is there any command to check whether the switch Layer(Layer 3 or 2) in CLI?
1
vote
1answer
108 views
Transporting an Ethernet Port in a LDP Based VPLS Instance on Juniper MX routers
We are currently transporting an Ethernet Port using LDP Based Layer 2 VPN service (P2P PW) in Juniper MX.This P2P LDP PW is up and currently working. Below is the configuration against this:-
set ...
2
votes
1answer
105 views
In RSTP, where all switches generate their own BPDUs, are they limited to forwarding them only on designated ports? (like in classic STP)
I recently learnt a rule in STP: only Designated ports forward BPDUs.
However, I'm not sure about this in RSTP since ALL switches generate their own BPDUs every few seconds. So, in a certain LAN ...
0
votes
1answer
29 views
Where can I find virtual switches to learn about layer 2 [closed]
I am learning about layer 2 networking, arp, cam tables, mac addresses etc. I will like to see some of these things in action but I do not have access to physical hardware now, does anyone know of a ...
1
vote
2answers
54 views
How does an L3 Supported Switch differentiate L2/L3 Packets?
I had a managed or layer 3 supported switch (it can process both layer 2 and layer 3 packets). Now a packet from a connected host comes to it, sending traffic. How does the switch decide to process it ...
0
votes
0answers
19 views
Switch vs. Router and sequence of OSI Model [duplicate]
As I understand it:
A switch (layer 2) seems to define a LAN and a router (layer 3) enables communication between distant LANs.
A device on a LAN will give it's MAC address to the switch upon ...
1
vote
2answers
64 views
Some extra clarification regarding VLANs and SVI
Good afternoon guys,
I've got a question regarding VLANs and SVIs.
First of all, I know some concepts about VLANs, and I've been in the IT field for a while.
But this one is a bit confusing for me.
...
0
votes
0answers
11 views
Query regarding ethernet header [duplicate]
I have a query regarding ethernet header.
Some representation of ethernet header have Type Field and some tell it as Length field.
Which is the right one here ?
0
votes
1answer
29 views
Why does SONET need atomic clock but T-carrier does not?
SONET and T-carrier are both synchronous TDM.
But T-carrier does not use atomic clock. Why does SONET?
Is it because SONET does not use buffer? But how does it prevent bit loss if there is no ...
2
votes
2answers
699 views
MAC address and unicast, multicast and broadcast
I'm very new to computer networking and I'm trying to figure out this dilemma about the Unicast, Multicast and Broadcast transmissions. I was told that MAC address are unique for each device and they ...
2
votes
2answers
50 views
What if my data contains nothing but Preambles and Start of Frame numbers?
Will that continually reset the receiving NIC or is there a sort of escape character that need to be used if my data contains nothing but alternating 1s and 0s in 7 byte blocks with start of frame ...
0
votes
1answer
34 views
Is SONET a physical layer or a data link layer?
According to some sources, SONET is physical layer.
But some sources say that SONET can carry IP directly. Also, SONET defines its own frame -- it has a header and a payload. That must make SONET a ...
1
vote
2answers
66 views
Query regarding LACP System Priority
This is regarding LACP System Priority.
From my research I could find the following info pertaining to system priority.
LACP combines the System Priority value with the MAC address of the switch to ...
0
votes
1answer
59 views
Query regarding LACP timeout flag
Say we have two swicthes.
Switch A and Switch B.
Switch A sends LACPDU's with timeput flag set to 1 (fast).
Switch B sends LACPDU's with timeout flag set to 0 (slow).
By researching came to know that ...
2
votes
3answers
190 views
Why is in all arp table snmp oids an interface index before the ip number?
When I want to get arp information about a single ip number or subnet, I have to snmpwalk the whole arp table, as some oid architects had the "great" idea to always insert an interface index ...
0
votes
1answer
32 views
BPDU Header System ID Extension
Previously network switches was using the 8 byte field Bridge Priority to identify a root on the network.When networks grows and becomes complex vlan creation comes into play the 2 bytes Bridge ...
0
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3answers
80 views
Propagating Static MAC Addresses
I have a situation where I need to place a static MAC on a switch as the server in question does not generate any outbound traffic. This static MAC seems as if it will work for hosts on the same ...
0
votes
1answer
44 views
How loops appeared when skipped listening and learning state?
In STP convergence process, I just know that after a link failed a blocking port become listening state for 15 seconds then learning state for 15 seconds. I've read a CCNA 200-301 Guide explained me ...
0
votes
2answers
45 views
Private VLANs Same As VLANs!
The common VLANs provides a layer 2 speration flooding and broadcasting is limited to each virtual lans.
Im wondering what is the purpose of the private VLANs also the secondary VLANs (isolated and ...
2
votes
2answers
86 views
When traffic is intiàted from pc is ANDing process or ARP process start working first
When traffic is initiated from desktop which process starts first; the ARP process or ANDing process?
1
vote
1answer
36 views
How a wifi AP handle packets
Computers are connected to a wifi AP. The wifi AP is connected to a L2 switch. A server is also conected to this switch.
When computers sends packets to the server, how the wifi AP manages the paquets?...
0
votes
2answers
147 views
Connecting switches together
I have L2 switches which will be daisy chained together (yes I know, daisy chaining isn't great, but anyway..) The L2 switches will then link to a L3 switch.
Both the L2 and L3 switches have x4 10GbE ...
1
vote
3answers
615 views
Minimum MTU size on Ethernet and minimum Ethernet frame size
I am a bit confused about the understanding of the relationship between minimum MTU of MTU and minimum Ethernet frame size.
We know that the maximum MTU of Ethernet is 1500 Bytes which makes the ...
3
votes
2answers
266 views
Confusion about MTU
I am studying about IP fragmentation and MTU. What I know is MTU is the property of Physical medium, as in the amount of data it can process without having to fragment the data. The default MTU on ...
1
vote
2answers
77 views
Is the outgoing interface of a router in the same Subnet as the Incoming interface of the NEXT HOP router?
In the TCP/IP Volume 1, it is stated that ARP works only on the same subnet. Does this mean that the outgoing interface of a router is necessarily on the same subnet as the incoming interface of the ...
0
votes
2answers
70 views
Layer 2 managed switch and layer 3 switch
If you have layer 2 managed switches which have VLAN's on them, do you still need a layer 3 switch/router?
1
vote
2answers
36 views
What is the need for the NEXT HOP coloumn in the routing table when we already mention the OUTGOING INTERFACE in another coloumn?
If the OUTGOING INTERFACE is already mentioned in the routing table, it is natural that the next hop will necessarily be the router attached to the outgoing interface. Then why is there a separate ...
0
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0answers
27 views
network cutover for remote site from L2 to L3 over IPSec tunnel
I have been trying to cutover one of our remote sites (A) to the new ISP we have purchased.
The existing setup is utilizing L2 through another remote site (B) and coming back to the main campus.
The ...
1
vote
2answers
218 views
Are all packets addressed with the MAC address of the router as they leave the machine?
In the Comptia Network+ All in One, it is said that most home routers have a switch built into them. It is also said that the first thing the router does is strip off any layer two information present ...
1
vote
1answer
131 views
Unicast and Multicast MAC address convention
I need help in understanding how Unicast and Multicast MAC address is differentiated as explained in wiki.
According to what I understood, when the least significant bit is set as 0 in the first octet ...
1
vote
1answer
10k views
difference between switchport trunk encapsulation dot1q and switchport mode trunk
I am new to network engineering and I am currently delving deep into L2 functionality.what is the difference between these two commands:
1 switchport trunk encapsulation dot1q
2 switchport mode trunk
...
0
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2answers
155 views
Network topology for merging two different layer 2 networks
I have a scenario, (shown in attach diagram)
where i need to merge traffic from two server 1 , 2 to target server 3. All three are on different vlans/subnets.
With layer 3 switch in between would it ...
0
votes
1answer
95 views
Why does the Layer 3 switch drop the ping packet?
I am trying to ping from PC2 (not PC1, there's typo in the picture) to the router's int g0/0, but the packet is dropped at the L3 switch which is along the path. I have tried setting a default static ...
1
vote
1answer
38 views
Can use virtual port as the port mirroring's destination port?
Port mirroring can mirror several source port to a destination port(mirroring port).
I have several questions about port mirroring.
in the dest port, how to differentiate the different source port? ...
1
vote
2answers
378 views
Vlan vs. Subnet Broadcast Domain
It is my understanding that Vlans separate broadcast domains, but I often see people say, "subnets define a broadcast domain" as well.
Is it correct to say, "Vlans define a L2 broadcast domain, and ...
