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For questions about the OSI layer-3 (network layer).

2
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2answers
187 views

How does the Transport Layer construct the Pseudo-Header for TCP checksum?

THE TCP Psuedo Header needs sender and destination IP Address and protocol type. All of this informations is present in the network layer/IP header. Since the transport layer cannot access the data ...
2
votes
1answer
24 views

Connect two VLANs on an NE1032 Lenovo L3 Switch

I just got a new Lenovo ThinkSwitch NE1032 with some 1G sfp. I have already created two VLANs called FE and BE that have the following IDs: 2,3. I have managed to assign an IP subnet to both of them, ...
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. ...
2
votes
1answer
179 views

Is There an Indication in Protocol Stack showing that the End Host is Mobile?

Suppose you are using the Web from your mobile phone. Is there any indication in the internet backbone, when you look at the traffic that shows that the end host is a mobile device? I am sure there ...
0
votes
1answer
34 views

Unable to reach a device on another net while having routes

I'm not sure what I'm doing wrong and would therefore need some guidance. The goal is to be able to have a SSH connection between: PC -> C On PC I have created a route route add 192.168.50.0 mask ...
2
votes
1answer
70 views

TCP connection question

Let’s say I have 4 ethernet interfaces getting IP addresses via DHCP. I make a TCP connection to a TCP server via one of the IP addresses on a certain ethernet interface. After the connection is ...
0
votes
2answers
73 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
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 ...
2
votes
1answer
53 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
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 ...
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
87 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 ...
0
votes
1answer
38 views

Routers and RIP violation of isolation?

I'm studying networking from the book 'A top down approach' from Kurose and Ross. In the book it is stated that routers are generally considered Layer 3 devices (i.e. implementing the stack up to ...
2
votes
1answer
244 views

At which layer does router operate?

I have studied from various sources that router is a layer 3 device. It does routing based on Network layer (layer 3) header, but I have a doubt. Network address translation (NAT) is a feature of ...
2
votes
1answer
60 views

Weird networking behavior with a gateway between a switch and CMC module, on Dell VRTX equipment. Am I doing something wrong?

Diagram: Here's the simplest way I know how to explain how the internal networking of this Dell VRTX works. So, you have your 4 blades and your network switch module that have integrated remote ...
5
votes
3answers
2k views

What are the reasons for seeing an incomplete ARP?

As was mentioned in this post: The reason for seeing an incomplete ARP is that "An ARP request was sent for that address, but the host with that address is not up and running on the LAN, so there is ...
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 ...
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:...
1
vote
3answers
459 views

When is 'Timestamp' and 'Timestamp Reply' are used in ICMP protocol?

I started the packet capture in my laptop through Wireshark application. Now through cmd, I pinged some server (say, www.google.com). And i stopped packet capture and analysed the packets being ...
2
votes
2answers
144 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 ...
3
votes
3answers
171 views

Layer 3 tunnel with Dynamic IP address

I want to ask whether it is possible to configure Layer 3 Tunnel with the two end points/interfaces have dynamic IP address? If the interface IP change, the tunnel will have to be re-negotiated, is ...
4
votes
5answers
715 views

Why can't two hosts (in two different logical networks) connected to each other through cross-over cable communicate?

Let us say, i have two computers (hosts) A and B. Where A has been assigned an IP address of 192.168.1.10/24 and host B has been assigned an IP address of 192.168.2.11/24. And both of them has been ...
1
vote
1answer
303 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 ...
1
vote
2answers
110 views

CGN and its advantages

I have been reading about CGN. Though similar to NAT it is used by service providers to route traffic without the need for the a public IP address. But when the packet leaves the ISP to the public ...
0
votes
1answer
83 views

Two Layer 3 Switches to one router

So I have a cisco 2811 router and 2 3560 switches Currently the router is connected to Core1 only, what i would like to do is use the other port on the router (fa0/1) to connect to Core 2. How do I ...
4
votes
3answers
352 views

How does a router a layer 3 device translate port address in PAT, as it is a layer 3 device?

While I was reading about PAT i.e Port Address Translation.The router was configured to translate all the private IP addresses to one single public IP.Since router is a layer-3 device, it can do that ...
3
votes
2answers
2k views

How to trunk VLANs over Layer 3 EtherChannel?

I am trying to setup a network that includes an EtherChannel link between two Cisco Layer 3 switches (Catalyst 3750). I am using a collapsed core hierarchical network. The picture above is my ...
0
votes
1answer
75 views

How to extend ports with L3 switch or other device? [closed]

I am a software engineer and no one in my team is familiar with network setup. My team recently bought 20 PCs for test our software but we only have 2 ports left in the room. And I have suddenly come ...
0
votes
1answer
763 views

Router vs VLAN in networking?

Why do we need Routers at all when we have VLAN ? Vlan breaks the broadcast domain. Vlan along with the use of SVI can be used for routing. So why do we need routers for in networking ?
0
votes
2answers
82 views

Is it possible to have a single port serve a layer 2 and 3 link simultaneously?

We are moving to a new L2 fiber network and i'm having trouble figuring out how to connect the DR. We are using a spoke and hub topology, with HQ as the hub. The branch locations all have unique ...
11
votes
2answers
6k views

VXLAN vs VLAN over layer 3

I read that one of the benefits of VXLAN over VLAN is that it can spawn across WAN and multiple layer 3 networks by creating overlay layer 2 networks. However AFAIN VLAN can also do the same using ...
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votes
2answers
205 views

Does a router divide a LAN into two seperate LANs, or a single LAN with two subnets?

The figure below is part of a networking homework question. The question asks about the source/destination IP and MAC addresses of frames sent throughout the system. My question doesn't touch on that ...
0
votes
1answer
58 views

Default Action in SDN Controller

In legacy IPv4 networks there exists a default route concept for routers where a router does not need to know exact destination of IP packet. Is there a default action concept for SDN switches? Let ...
1
vote
1answer
54 views

L3 routing between switches with some VLAN's trunked

During a migration various L2 equipment will be replaced with all Cisco L3 switches and over time traffic migrated to routed subnets instead of trunked. There are two straightforward approaches that ...
0
votes
1answer
54 views

Do packets take the same amount of time when they are within the MTU?

Without considering application processing or deep packet inspection, do packets that do not fragment all travel through the network at the same speed? For example, if there is a network with an MTU ...
1
vote
1answer
256 views

VLAN on Layer 3 Cisco C3560

I am looking to get a layer 3 Cisco switch and I know how to setup vlans, I will have the internet connection coming in from the pfsense router on port 1 and then vlan 10 on port 10 and vlan 20 on ...
3
votes
1answer
2k views

What's the difference between port number and protocol number?

Can someone explain it clearly. I know that port numbers are used by applications to differentiate which services you have requested, and routing protocols use protocol numbers in TCP header.
2
votes
4answers
462 views

Network service that is both connected and connectionless

I'm reading through Kuross "Computer Networking, a Top Down Approach". In the chapter about the network layer, they mention "In all major computer network architectures to date (Internet, ATM, ...
2
votes
1answer
124 views

Why does a layer 3 hop use vrrp secondary on nexus 6001

I have a nexus N5K-C5672UP as core layer 3 for our VLAN's. VLAN 601 on core 2 is secondary vrrp: core 02: core02# show vrrp Interface VR IpVersion Pri Time Pre State VR IP addr ---------------...
1
vote
1answer
111 views

Basic understanding of network operation

Assume two stations, A and B, are connected by two intermediate routers. A----R1-----R2----B Now, when A sends a packet to B, then the OSI model will come into the picture. Like, A's TCP layer will ...
0
votes
1answer
379 views

Cannot access Internet from VLANs on an HP layer 2 and layer 3 switch

I have got an HP switch, layer 2 and layer 3 capable. I created some VLANs. I have an ADSL router on VLAN 1 with the IP address 192.168.1.2. From VLAN 1, I can access Internet, but from the other ...
1
vote
1answer
106 views

VSS for layer 3 only 6500

I have 2 6500 at the core, that have only L3 links to the DC and the campus. I'd like to set VSS but I'm wondering if it's possible in such scenario. It uses OSPF for the routing. I'll have the ...
0
votes
1answer
729 views

What is the proper switch configuration for the switch that is connected directly to ISP source?

The Question: What is the proper configuration for the L3 switch to be allowed to assign public IPs for the firewalls? I guess All I need is that the switch L3 act as a layer 2 switch...Right? ...
2
votes
1answer
47 views

Host behavior with mask +1 and -1

Let's suppose I have a configuration: host: 192.168.1.145/25 gateway: 192.168.1.129 network: 192.168.1.128/25 broadcast: 192.168.1.255 What happens if I add +1 bit and remove -1 bit to the mask? 1) ...
0
votes
1answer
352 views

How do we find the host name name by using mac address,VLAN or IP address on Layer3 switch [closed]

have quick question How do we find the host name name by using mac address,VLAN or IP address on Layer3 switch . i pull up the vlan and mac address using my IP by i couldn't figure it out the host ...
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vote
2answers
1k views

How to make two Cisco switches talk to each other

I have a layer 3 switch with multiple VLANs. I created a trunk port that connects to a layer 2 switch. I can now successfully access the layer 3 switch VLANs from an access port on the layer 2 ...
1
vote
1answer
208 views

In IPv4 does the identification field in a TCP packet change for fragmented packets?

If a TCP packet is fragmented then would the identification field of the header stay the same for all of the fragmented packets, or would it increment by 1 so that the receiver would know what packet ...
5
votes
3answers
3k views

Layer 3 Switch Routing vs Router on a Stick

CORE: Dell N4032 (6.3.0.18) Access: Dell N2048 (6.3.1.13) We are in the process of setting up a serviced office that will serve multiple businesses. Each "customer" will naturally be on their own ...
2
votes
1answer
2k views

Designing a redundant switching infrastructure

Ultimately I've been tasked with the installation of a serviced office with upwards of 1000 staff, potentially being spread across 50+ VLANs. The hardware bought was out of my hands, but it's fairly ...