Questions tagged [layer3]

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

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Cisco VRFs and L2 inter-switch communication

I am having trouble wrapping my brain around a VRF concept and why two switches are communicating with each other on a particular VLAN when I don't think they should. switch1 & switch2 are ...
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4answers
4k views

In the TCP/IP model, how does the application layer inform the Internet layer of the destination IP address?

New to networking. How does the application layer inform the Internet layer of the destination IP address? Let's say I make a Http request to www.google.com, which the application layer resolves to 8....
1
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1answer
764 views

Ping over Trunk Port Juniper

Let's say I have one vlan on one switch and another vlan on another switch (2 EX2200 Juniper). I have a trunk between the two switches on which both vlans are members. What do I need to do to allow ...
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1answer
522 views

Calculation accounting for Layer 2 overhead when viewing traffic statistics

Recently, I was on a Juniper device, trying to figure out why I was getting a lower bit rate even though I knew I was sending a lot more. Then it hit me that Juniper devices show the Layer 3 ...
0
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2answers
20k views

How do you ping between VLANs?

I have created VLANs on the layer 3 switch and I would like to ping between them, how do i do so? I would like to allow VLAN 2 to ping VLAN 3, how? What command should I use? new#sh ip interf ...
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1answer
414 views

Multicast forwarding through VLANs for KVM Over Ip [closed]

I'm currently designing a terminal-server architecture, using KVM-Over-IP technology (I'm using Gefen devices) where I have four VLANs: One VLAN for the displays at 192.168.240.0/24 Three VLANs for ...
5
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2answers
4k 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?
2
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1answer
285 views

Problem with Routing in VLAN

I am trying to set up several VLAN's on a Cisco 3560 switch. These new segments should be able to communicate with VLAN 1 and even access the Internet. Basic IP information: Gateway: 10.1.1.2 VLAN1: ...
2
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2answers
692 views

On a Layer 3 switch, what part does the CPU play in forwarding packets?

I am a Systems Administrator at a small firm. We are latency sensitive. When forwarding packets, what protocols use the CPU and which use the ASICs? We have mostly Arista 7124's (for the most latency ...
2
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1answer
1k views

Load balancing between multiple layer 3 switches

I have two trunked L3 switches forming a network backbone. One is an old HP2848 and the other is a new Juniper EX3300. Currently only the EX3300 connects to our WAN Router and is trunked via 4 LACP ...
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3answers
1k views

Routing between two networks

I had a question here. Basically, we have two different networks. Each network has one Cisco 2960 layer 2 switch for each network in the same location. These are two individual networks. There is a ...
2
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1answer
126 views

How can fat tree ensure bandwidth?

I'm reading about fat tree and data center topologies, but I have doubts. To lower cost, "normal" tree is used sharing bandwidth to many hosts. 1:1 is not common, so we see something between 2.5:1 ...
2
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2answers
957 views

Exiting to a Router from Layer 3 Switch with SVI enabled routing

I am trying to simulate a network, I am having problem directing traffic to exit the L3 Switch and to go to router for routing to outside network. (I don't want to use routing capability of switch, ...
1
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1answer
934 views

How to use a layer 3 switch for QOS between gateway and hosts?

In the following scenario, is it possible to prioritize VOIP/RTP from x.x.x.51 through the gateway with a Cisco switch, and how? I need to prevent x.x.x.50 from saturating the WAN connection. ...
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1answer
76 views

General network comprehension

I wrote a program that does packet communication with a server and something has been in the back of my head for sometimes : When I analyze packets with WS I can see in the header first off two MAC ...
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3answers
3k views

Assign IP address to a FastEthernet port on CPT switch

I've configured a vlan 3 with ip address and then assigned FE port to vlan 3 , i read that this will assign the ip address to the FE interface. I know this is really simple configuration .But really ...
0
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1answer
657 views

theory: connecting two computers with ethernet cable [closed]

I am fairly new to networking but have done manual Linux command line wireless connections and home router configuration. The internet is full of how-to guides on transferring files between two ...
1
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2answers
321 views

How does a TCP segment go through the Internet Layer in TCP/IP?

I'm currently learning the reference models. It's said that TCP/IP supports only connectionless communication in the Internet Layer but both connectionless and connection-oriented in the Transport ...
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0answers
370 views

Optimizing access control lists on a Cisco SG500X-48 Small Business switch

I am trying to optimize the access control list rules on a Cisco SG500X-48 Small Business switch (on Layer 3). The general aim is to regulate the traffic between two VLANs (e.g., 10 and 30) in such a ...
4
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3answers
765 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 ...
7
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3answers
11k views

What is the difference between layer-2 and layer-3 broadcasts? Please explain with an example

What is the difference between broadcast addresses ff.ff.ff.ff.ff.ff (Layer 2) and 255.255.255.255 (Layer 3)?
6
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5answers
1k views

Inter-VLAN Routing

I am trying to configure inter-VLAN routing, but I can't route using MLS. I attached the image. Please check and give the answers. In switch0 I created VLANs 2 and 4; in switch1 only VLAN 3; in ...
2
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1answer
2k views

InterVLAN routing with one layer 3 switch

I'm looking to set up InterVLAN routing with one layer 3 switch within Packet Tracer (multiswitch), and then have 12 machines connect to these switch. The 12 machines are split between 4 VLAN's as ...
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4answers
2k views

Accessing devices on different subnets using a switch

I have two devices which come up with default IP addresses: Device 1 - 192.168.168.168 mask 255.255.255.0 Device 2 - 192.168.1.254 mask 255.255.255.0 I can commonly deduce that both the devices ...
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1answer
2k views

VLAN Tags and QoS

I have a bunch of phones that are tagged as VLANID 20 with priority 7. I have the router setup with VLAN Tagging as well to mark VLANID 20. My question in terms of switches. Do the switches need to ...
6
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4answers
2k views

Why is the ICMP protocol considered to run at layer 3 on the Wikipedia page?

Why is the ICMP protocol considered to run at layer 3 on the Wikipedia page (same layer as IP) when the ICMP protocol data is a payload of the IP packet? This is the article on Wikipedia that states ...
2
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1answer
98 views

Cisco MLS - single port carry L2 and L3 packets

While learning networking concepts I learn a network hardware port can be switch port to carry MAC headers or Routed port to carry L3 info. However, Cisco MLS concepts as I understand a switch port ...
4
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3answers
209 views

Campus Area Network questions

Looking for design principles in regards to a Campus Area Network? We are a medium sized company with < 250 employees spread across 4 offices. We will soon be combining 2 offices into 1 larger ...
18
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3answers
8k views

What do TCP/UDP add to “raw ip”?

I know that both TCP and UDP are built on top of IP, and I know the differences between TCP & UDP, but I'm confused about what exactly "raw ip" is. Would it be fair to say that TCP & UDP both ...
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2answers
116 views

Cisco Nexus 6004 Layer 3 capabilities

My organization currently has a pair of Nexus 7010's (Sup-1's) in one of our smaller data centers as our core switch (we still currently implement a Core-Dist-Access model). Long story short, this ...
2
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1answer
3k views

Does the spanning tree protocol come as standard in L3 switches? [closed]

Online there is a lot of content mentioning the spanning tree being a l2 switch feature so I guess it comes as standard/ is a given that it available for all modern l3 switches... (Could the answer be ...
3
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3answers
3k views

Cabling standard for Layer-3 switch

I want to know the appropriate cable type between: Layer-2 and Layer-3 switch Layer-3 switch and router Is it cross-over or straight through?
9
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4answers
3k views

Advantage of layer 3 switch over Router

What is the advantage of Layer 3 switch over the Router ??
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1answer
371 views

Why PPP cares about network layer?

Why PPP have protocol field? Isn't whole purpose of partitioning communication system to have simple isolated subsystems?
3
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3answers
6k views

What is the difference between ff-ff-ff-ff-ff-ff (layer 2 broadcast) 255.255.255.255 (layer 3 limited broadcast)?

Please explain the flow of traffic in each case.
2
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1answer
162 views

Where exactly is the limited broadcast address used?

I read that limited broadcast address will be dropped by the router. So, it's not used in the layer-3 (Network layer), where IP addresses are meant to be used. So, where exactly is it used?
1
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1answer
617 views

Is “Layer-3 switch” a combination of router and switch?

I noticed there are some switches called "Layer-3 Switch", which is able to do both switching and routing. I have seen some articles that says Layer-3 switch can replace routers. Is it going to ...
9
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3answers
1k views

What is a “Layer 3 Switch”?

What is a "Layer 3 Switch"? I essentially understand the OSI model, well maybe I don't and maybe that is why I don't understand. Its just that I don't see how/when/if a "managed switch" becomes a "...
2
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3answers
4k views

What is the relationship between the IP address and MAC address?

I own a MAC address and I want to know from it, the IP address.
4
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1answer
2k views

Help with VLANs, ACLs, DHCP on SG-300 Layer 3 switch

I have to do the following configuration on an cisco Sg-300 small business L3 switch as in the figure. Since i don’t have access to this switche for practice before doing this live in production i ...
5
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5answers
332 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 ...
2
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1answer
62 views

Inter Vlan Packet Transfer

I am trying to establish communication between 2 devices within different vlan. But I require a router for that. Can I send packets within different VLAN without having a router or a Layer 3 device.
2
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3answers
2k views

What is Routing Daemon?

Reading about IP Routing, I found a brief explanation: "routing daemon, which is normally a user process. The most common daemons used on Unix systems are the programs routed and gated." In an Unix ...
2
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2answers
514 views

IP Fragmentation

When Device A sends an IP datagram toward Device B, the IP Layer of Device A computes if it must or not fragment the IP datagram to fit the link MTU. Sent to the next hop, the process will be repeated....
3
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2answers
499 views

SonicWALL TZ215 : 2 LAN interfaces and 1 WAN

Here is network schema: 192.168.2.200 - Switch layer 2 ---| |--X0 LAN 192.168.2.254 |---Switch layer 3 ---| 10.50.40.40 --- Swtich layer 2 ---| ...
2
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1answer
155 views

How do I use my SP Ethernet connection between HQ and Branch for Layer 2 and Layer 3

I am looking to use my provider Ethernet Connection between our HQ and Branch to do Layer 2 and Layer 3. The Ip addresses I hope to use for the remote are those being advertised to the ISP using BGP. ...
6
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1answer
4k views

Assistance with routing between layer 3 switches with ospf

I have two Cisco 3560's in a branch office. One acts as an access switch configured with two vlans: interface Vlan10 ip address 192.168.0.254 255.255.255.0 interface Vlan20 ip address 172.16.0.254 ...
2
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1answer
287 views

Metro Ethernet no layer 3 connectivity

We're working with a metro ethernet provider to bring up a new multi-point connection between our sites. Currently we're just trying to get it working with two sites. As a simple test I've plugged in ...
5
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1answer
306 views

Optimizing Network Topology

Recently I wish to split the network by VLANs. Mainly for two reasons Exclude management interfaces from the commonly accessible lan Separate WiFi traffic (security and broadcasts) The current idea ...
3
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1answer
11k views

Can same port configured for different IP address or different protocol

I read following line from port WIKI So, does it mean that same port, let's say 7001 can be bind to a different IP address or different protocol? As per my knowledge, it cannot be and would result ...