Questions tagged [layer2]

For questions about the OSI layer-2 (data-link layer).

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7
votes
3answers
4k views

Does a switch understand packets? If yes, what is the frame terminology for?

I was a little confused between packet and frame. The confusion was based on, if a switch is a layer 2 device, how does it reads a packet from a layer 3 device, and where is the 'frame' thing which is ...
5
votes
2answers
3k views

How does a layer-2 switch work with UDP?

If UDP and/or TCP send packets via IP to an Internet Protocol Address, how can a layer-2 switch forward these? Is this possible or do you need a layer-3 switch?
3
votes
4answers
150 views

Need of routers and IP addresses

I dont know if my research is enough or not but I could not find answers on the net. My question is why not use bridges instead of routers. We know bridges can connect two different networks. Using ...
3
votes
3answers
327 views

Is it possible to perform a Layer 2 (MAC address) traceroute?

I understand the difference between layer2 & layer3 and MAC & IP. I understand address resolution protocol, etc. But is there any way to do a traceroute that will show Layer 2 information? For ...
17
votes
6answers
55k views

What, exactly, is required to make Airplay work across VLANs? [closed]

It seems like AirPlay works out-of-the-box, vaguely speaking, only within a LAN. It's not clear to me exactly why, but it looks like at least discovery relies on broadcasts. Wikipedia states that ...
16
votes
3answers
61k views

How is the root bridge elected in STP?

How does STP/RSTP determine which bridge is the root bridge, and how are paths to the root bridge selected?
4
votes
3answers
9k views

Inter-switch IGMP on a VLAN with two switches, and a multicast source per switch

I have a network consisting of two HP 2810 switched. Attached to each switch is, on one port, a multicast video coder, and on a different port, a decoder. There are two VLANs - a control VLAN (...
13
votes
4answers
16k views

MTU and Fragmentation

Consider the following: NAS with 10G interface connected to 10G interface on switch. Client computers connected to switch via gigabit Ethernet. Will there be any gain in performance if MTU size is ...
5
votes
2answers
9k views

Why each and every single port on Layer 2 switches need to have it's own MAC address?

A switch doesn't alter the frame, and source/destination mac addresses remain how sending host specified them,so let me say it again Layer 2 Switching never changes the frames means no changes in MAC ...
10
votes
1answer
10k views

RIB vs FIB differences?

Can someone explain the differences between a RIB and FIB a little further? I didn't see any similar questions on the site so I thought this would be a good addition. The RIB routes and the FIB ...
3
votes
2answers
3k views

Do broadcast (FF:FF:FF:FF:FF:FF) packets go through the router, or directly all computers on the subnet?

If you have the destination MAC address you need in your ARP cache, surely it shouldn't have to go through the router? Or is that the point - only the router can be sure to have all of its subnet's ...
12
votes
1answer
2k views

Can a router send ARP requests to hosts?

I play with libpcap in C recently to create an arp sniffer program that captures arp requests on the air. I came up with a strange effect. I captured arp requests from my router. I don't know if this ...
7
votes
2answers
419 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 ...
5
votes
5answers
287 views

What blocks a computer from another network in the same switch from answering an ARP request?

Let's suppose I have 3 computers A, B and C connected to the same switch with only the native VLAN active. A and B belong to the same network, let's say that their IP addresses are 192.168.1.1/24 for ...
4
votes
3answers
555 views

What practices/ mechanisms/ protocols can be used to secure communication on physically exposed Ethernet links?

Given that Ethernet cables are everywhere and use for all kinds of links and it is assumed they are physically guarded, hence typical installations do not leverage any "secure" mechanisms. Let's say ...
3
votes
2answers
433 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 ...
3
votes
3answers
6k views

D-Link L2 & L3 Network Setup

I'm currently setting up my new network using D-Link DGS-1510 series gigabit stackable smart managed switches. It is the first time i use this L2 & L3 switches and I'm trying to setup the ...
2
votes
3answers
582 views

Does a router send frames or packets?

Perhaps it's a novice question, but does a router send/receive frames? When I read about this subject, it seems that routers decapsulate the frame on arrival, and encapsulate the packet in a frame in ...
2
votes
4answers
1k views

Should I receive an ARP reply from a host that is logically on a different subnet but is connected to my host via a hub?

Host A: 128.238.66.100/16 Host B: 128.238.67.100/24 The hosts are connected to the same hub and nothing else is connected to that hub. The routing and ARP tables of both hosts are empty. Host A ...
1
vote
1answer
216 views

DTP mode desirable and on

the on mode still negotiable (send/receive DTP) until i set it no negotiate so what is the Difference between on and Desirable. please give an example :))
1
vote
1answer
990 views

Relation between Ethernet and 802.11 headers

I would like to ask about the relation between 802.11 and Ethernet L2 Link layer. Are they dependent of each other? Or can they be seen as independent L2 link layers (with only similarities in ...