Questions tagged [link-layer]

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Shared layer 2 state in a P2P Tunnel between two Linux Machines

Assume two Linux Hosts, that are directly connected to each other cia ethernet and their ethernet interface is always up. I am wondering if there is a tunneling protocol implementation that would ...
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Forwarded Packets are received by namespace's veth0 but not received by application

I use libtins (It uses Pcap) to capture link layer packets and forward to a network namespace where the actual application runs on. Client(Browser) -> Server -> Pcap -> Pcap Send -> br0 (...
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1 answer
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Different MAC addresses in packet and ARP table

What happens if a host on the network receives an IP packet with a MAC source address that differs from the MAC address in the local ARP table for that source IP? The ARP table entry for that IP was ...
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3 answers
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Can data link layer do IP fragmentation in some special cases?

I'm reading book TCP/IP Illustrated, Vol.1 and there it says that IP fragmentation is done by network layer. This is how I understood the concept so far: Network layer (L3) creates "IP datagram" (IP ...
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How to setup an encrypted L2-Tunnel using MikroTik Routers?

What I would like to achieve I want to securely spread an existing internal subnet over multiple buildings. That means that I have two locations with virtual machines that need to be within the same ...
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3 votes
0 answers
515 views

How to get the topology of a layer-2 switch network with the switches' forwarding tables?

Suppose I have a list of layer-2 switches that do not support LLDP (Link Layer Discovery Protocol) but support SNMP. I have the management IP addresses of these switches, but I don't know how they are ...
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1 answer
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Blindly bridging wireless client with MAC NAT

This is the usual "I want to bridge wifi with ethernet" question, but I need something specific here. My Linux box has a wlan0 interface which is in station mode, with MAC aa:aa:aa:aa:aa:aa, and a ...
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RHEL6: bonding NICs with DHCP reservation problems

I am using a 4 NIC bond with Bonding Mode: transmit load balancing and a port channel is configured on the switch. I have a DHCP reservation for the IP address being used for the bond. I configured ...
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2 answers
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Comunication between LANS using layer 3 switch only

I have a LAN-A with VLANs 10,15 and a layer 3 switch-A used to communicate between VLANs 10 and 15. This LAN is working OK. I have a LAN-B with VLANs 60,65 and a layer 3 switch-B used to communicate ...
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4 votes
2 answers
3k views

ARP responds with single MAC address on Linux server with multiple interfaces on the same network

Linux server has 2 active network interfaces: IF:eth1 IP:192.168.1.1/24 MAC:11:11:11:11:11:11 (1GbE) IF:eth2 IP:192.168.1.2/24 MAC:22:22:22:22:22:22 (10GbE) The idea is that the ...
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Layer 2 bridged networking issue with QEmu

I am having a problem with a layer 2 bridged network configuration using Linux, QEmu, and VMware ESX. The configuration works fine on a small isolated network, but once introduced into our large ...
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Layer 2 Load-Balancing on redundant Architecture

Some PCs with 2 NICs are bound on 2 Switches in order to avoid a Single-Point-of-Failure (the switches are interconnected to each other too). Under which cirumstances is it possible that the PCs can ...
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2 answers
486 views

Duplicate IP on network and layer 2 devices caching

I have two identical VMs (Windows XP guests). I use KVM for the hypervisor. The first one is running, the second is a clone of the first not yet running. I edited the config for the second one to ...
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1 vote
4 answers
7k views

Cisco Switch: trigger mac-address table update

If I run show mac-address-table dynamic I get a bunch of mac addresses on that table. But due to the aging parameter, I don't see the mac addresses of all possible devices on the network that come ...
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14 votes
1 answer
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What are the data link protocols for cellular networks? [closed]

What are the link layer protocols for cellular networks? There are several platforms for high speed cellular networks. From GSM, to GPRS, W-CDMA, HSPA, LTE, etc. I (mostly) know about the physical ...
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2 answers
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2 networks with a layer 2 bridge that shouldn't be there.

I have 2 separate networks that I manage. They have a router between and layer 3 connection is working fine. Last week my DHCP servers started handing out IPs across the networks, looking around I ...
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1 vote
5 answers
387 views

About the link layer of TCP/IP

I know there're ethernet,token ring,FDDI ,etc protocat the link layer, but how to know the exact protocol used to perform a specific task,like browsing a web page?
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4 votes
3 answers
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Network link layer equivalent of `ping` to probe a device which fell from the intranet?

Here's my situation. It's hypothetical, but happens often enough to be a problem. We have a generic layer 2 ethernet network switch. All of the devices connected to this switch use IP addresses in a ...
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2 votes
2 answers
109 views

Need confirmation on layer 2 security question

I need confirmation on a question regarding layer 2 security. I've been doing research and I just need to know that I understand it correctly. Basically, if you have a LAN with a few machines ...
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1 vote
1 answer
8k views

How many bits for sequence number using Go-Back-N protocol

I'm a regular over at Stack Overflow (Software developer) that is trying to get through a networking course. I got a homework problem I'd like to have a sanity check on. Here is what I got. Q: A ...
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8 votes
7 answers
3k views

Should Cat6 cables be used for servers ('important hosts') rather than Cat5-E?

Wouldn't you want your crucial hosts being served with the most signal-reliable/improved method of connectivity? Gig Switch<->Cat5E<->Server? or Gig Switch<->Cat6<->Server? My ...
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