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Questions tagged [layer3]

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

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27 views

Unicast Adjacency Routes Nexus (AM) Cisco Nexus

I have an odd situation. There is static route on my Nexus 7700 that routes anything for specific subnet /24 to a F5 LTM Load Balancer, external VRRP interface 10.x.153.15. As you can see below, ...
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0answers
17 views

How many IP fragments are sent? [closed]

An IP Packet of size 5,730 bytes is sent over a link with a 600 byte MTU How many IP fragments are sent? Fragment 3 is lost, will the IP layer request retransmission?
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1answer
34 views

What is the advantage of Supervised Machine Learning over Deep Packet Inspection in Network Traffic Classification?

As per the definition of Deep Packet Inspection (DPI), it uses signatures for packet filtering. Supervised Machine Learning can help put a label on a packet which does not get identified by Deep ...
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3answers
2k views

How does Deep Packet Inspection work with encrypted packets?

I've been reading up on Deep Packet Inspection for Software Defined Networks. However, I know that some applications use encryption to evade Deep Packet Inspection. Is there any alternative (such as ...
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1answer
50 views

What is the theoretical difference between the link layer and the network layer?

I have run into this problem again and again and have never found a sufficient answer to this question. I want to understand the fundamental, theoretical difference between a layer 2 network and a ...
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4answers
42 views

ACL on routers to block TCP/UDP ports

How routers understand the layer 4 port numbers to be blocked in ACL? When an ACL to block TCP/UDP traffic with certain port numbers is applied on a router/L3 interface , how will router understand ...
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0answers
16 views

how OSI and TCP/IP layers work? [duplicate]

I am really confused by how the layers these model work. I'm not asking about what are their functions. I read that transport layer provides end-to-end of all packet delivery, and networking also ...
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0answers
13 views

Why we need routers when there is layer 3 switches [duplicate]

I know that routers only do routing but layer 3 switches can do both switching and routing. my question is why we still need routers when we have layer 3 switches ?
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3answers
67 views

Regarding Cisco's hierarchical network design

why routed ports usually implemented between the distribution layer and the core layer ? why not just extend the layer 2 domain to the core layer ? is the other design model more practical than this ...
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0answers
19 views

Are there any other notable protocols besides IP on OSI layer 3 in the internet? [duplicate]

Are there any other notable protocols besides IP on OSI layer 3 used in the internet?
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2answers
61 views

switch died after slow to rapid failure now DHCP will not function across network even with new switch

ok so i'm running out of ideas here. we have/had 3 managed switches in our server rack and one in a closet; one hp procurve 3500yl 48 port with poe for 2 APs and 2 catalyst 2960s in the bottom of the ...
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3answers
298 views

Leaf-Spine network without routing

If I have a leaf-spine network with all the servers on the same subnet, say 10.10.0.0/16, do I need a router (or l3) since everything is on the same network and the network is flat?
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2answers
76 views

Why do transport layer do data chunking. If there is fragmentation in Network Layer

I just curiously wanted to know about the question regarding L4, L3 Data Chunks, IP Fragmentation : Data chunking happened at Layer 4(Transport, TCP), and Fragmentation at Layer 3(Network, ipv4) ...
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2answers
103 views

Different MAC addresses [closed]

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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2answers
105 views

Is a “LAN” a layer 2 or a layer 3 concept, in TCP/IP?

I think my question is purely theoretical and a matter of definitions; it derives from the fact that a L2-switch with VLAN capabilities is able to "create" different virtual LANs, and thus I am led to ...
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1answer
76 views

Layer 2 and Layer 3 traffic with one cable

Hers the topology. L2 switch L3 switch Router There are 2 VLANs. One VLAN ends on the L3 switch 1 VLAN on the router. Here is the question. Can i connect the L3 switch and the router with just 1 ...
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2answers
231 views

What are neighboring ports?

I know this is as basic as it gets but I can't find a direct answer to this question. Are they ports on two different switches (or routers) that are connected by a cable? Are they the ports ...
2
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1answer
19 views

Understandable/Implementable explanation of CSMA p - persistent

I have been trying to understand how the CSMA P-persistent method works, but haven't been able to understand how it's implemented. I have referred to a few textbooks and other sources, but all of them ...
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0answers
17 views

DHCP Layer 2 and Layer 3 [duplicate]

I am having a difficult time to visualize the conceptions of DHCP Discover message in order to receive an IP address sends out a broadcast at both layer 2 and layer 3. Can someone care to explain? ...
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1answer
242 views

Arp Cache Timeout [closed]

I'm trying to poll the arp table from a backbone switch but i want to understand which records are up. I just want to know if there is a specific time for the switch to keep a record on the arp table ...
3
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2answers
124 views

Is static routing used in large networks?

I'm a beginner in networking stuff and just wondered if Static Routing has any use in large networks ? How about small ones ? In which cases we prefer to use static over dynamic routing ? I searched ...
3
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1answer
437 views

MAC Table vs ARP

I understand that for a switch to learn a MAC address, if host A wanted to send data to Host B the switch learns host A MAC and places it in the MAC table. If it doesn't know where the MAC (for Host B)...
2
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1answer
546 views

Successful Intervlan Routing on a Layer 3 Switch, Unsuccessful IP Routing

Hello and thank you in advance for your help! I'm using Packet Tracer for testing purposes and I' m trying to implement a simple intervlan routing in a Layer 3 Switch (3560-24PS) and an IP Routing. ...
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3answers
545 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 ...
2
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3answers
676 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 ...
3
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2answers
184 views

Mgmt Vlan vs other SVI s

Think of a layer 3 switch. Assume that we have a management vlan and a mgmt vlan interface. And we have other svi's on the switch. The question is this. I know that mgmt vlan is for telnet/ssh, simply ...
3
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1answer
279 views

Cisco ARP cache rewrites?

I know that the Cisco's default ARP entry expiration is 240 minutes, however how does the ARP table mechanism work when a different MAC address is seen using the same IP? In other words, if I move ...
2
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1answer
73 views

Is it worth the effort to split up in layer 3 with point to point links? [closed]

I have this technical question. With my family we have a little business. I got to provide internet access to three places, separated a few hundred meters each other. I need to allow to watch the ...
1
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1answer
79 views

HP 2920 Routing

I am working on setting up routing on a HP 2920 to a firewall. I can not figure out what I need to do to get this set up. I know that the ip routing command turns on routing and the ip route ...
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2answers
33 views

How can subnets not fulfil symmetric property?

While studying Internet Protocol, I came upon the following example of two devices: Device A: IP address: 10.1.1.1 Subnet mask: 255.255.255.0 and Device B: IP address 10.1.1.200 Subnet mask 255....
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1answer
495 views

Firewall on a stick for Intranet and static routing

I have a question about possible problems that can occur with this network design. If I have an intranet with a firewall on a stick design, multiple switches with layer 2+, is this setup fine? or ...
1
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1answer
226 views

Help with small office setup - Cisco SG350 28 port switch

I have very limited knowledge in Cisco IOS but in a crucial state to setup up a small office network. I have bought 2 Cisco SG350 28 port Layer 3 switch, Switches should be enabled with VLAN and VTP. ...
3
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2answers
767 views

L2 / L3 on CISCO ASR

I am new to CISCO and have the following problem: I have 3 routers. Between these only one physical connection. The VLAN 100 is connected to R1 and R2. The VLAN 200 is connected to R1, R2 and R3. The ...
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1answer
279 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, ...
4
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1answer
689 views

Cisco 3172 asks for LAN_ENTERPRISE_SERVICES_PKG license to enable OSPF and PIM when they are LAN_BASE_SERVICES_PKG license features

I have several Nexus 3100 switches in which I use OSPF and PIM. Cisco says that these features are included in the LAN_BASE_SERVICES_PKG which is included by default in the switches. Switch1# sh ...
4
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4answers
1k 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. ...
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2answers
343 views

Inter vlan routing not working

Apologies if any details not clear as I'm not a network expert. I have a Procurve 3500yl layer-3 switch. I am trying to make two VLANs and get a PC in one VLAN to connect to the other VLAN. Below is ...
2
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1answer
188 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 ...
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1answer
37 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
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1answer
98 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 ...
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2answers
466 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 ...
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3answers
136 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 ...
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2answers
227 views

Routing specific TCP/UDP packets from VLAN's to proxy server

I need to set up a solution which is for routing specific TCP/UDP packets between the devices in two separate VLANs through a proxy server. For eg: all my computers are connected to one VLAN(1) and my ...
4
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2answers
2k 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 ...
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1answer
37 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 ...
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5answers
479 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 ...
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1answer
478 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 ...
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1answer
64 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
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2answers
1k 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 ...
4
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1answer
82 views

How does Junos distinguish that route is learned in Layer 3 or Layer 2 VPN environment?

As I understand from Understanding Junos OS Routing Tables document, then bgp.l3vpn.0/bgp.l3vpn-inet6.0 or bgp.l2vpn.0 tables contain routes learned from other PE routers in Layer 3 or Layer 2 VPN ...