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Questions tagged [layer3]

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

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5
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3answers
6k 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
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4answers
36 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 ...
1
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3answers
2k views

Juniper EX how to clear route forwarding table?

After layer 3 routing a large IPv6 assignment on an EX Juniper switch, the route forwarding table filled up and some entries corrupted or became otherwise invalid. We want to clear the whole table. ...
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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 ...
0
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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 ...
0
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0answers
12 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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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
60 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 ...
4
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3answers
280 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?
0
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2answers
72 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) ...
0
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2answers
102 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 ...
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 ...
1
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2answers
102 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 ...
0
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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 ...
33
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3answers
95k views

What is the difference between MSS and MTU?

I'm confused as to the difference between maximum segment size and a maximum transmission unit. Can someone please explain in relation to layers 2 and 3? If I had a packet of 800 bytes in the ...
4
votes
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 ...
2
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2answers
230 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 ...
3
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2answers
461 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 ---| ...
3
votes
3answers
2k 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?
2
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1answer
18 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 ...
0
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0answers
16 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? ...
0
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1answer
218 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
votes
2answers
118 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
votes
2answers
172 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
votes
1answer
391 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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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 ...
2
votes
1answer
495 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. ...
1
vote
1answer
73 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 ...
3
votes
3answers
437 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
637 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
votes
1answer
266 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
votes
1answer
66 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
vote
3answers
801 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 ...
3
votes
2answers
9k views

Mac address and IP address in physical addressing in Data-Link layer

Framing is done in Data-Link layer. We give physical addresses there. Destination address, source address and MAC. If two PCs in different networks, we try to sent data from one another, we specify ...
2
votes
2answers
482 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....
1
vote
1answer
426 views

Help setting up multiple IP ranges on same subnet

So long story short. We setup our network YEARS ago, when we were a small company of only 10 people. Now, we are pushing 100 employees, and my network has outgrown itself. Originally, I setup the IP ...
3
votes
4answers
152 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 ...
4
votes
2answers
562 views

Can I Use BGP as an IGP - Multisite w Redundant Layer 3 MPLS WANs

The requirements are Hundreds of sites. Each has a router and firewall and a switch stack. Layer 3 MPLS WAN with BGP to provider VRF. BGP as an IGP? iBGP Would you distribute a public ASN across ...
2
votes
1answer
670 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 ...
4
votes
3answers
564 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 ...
5
votes
5answers
2k 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
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....
7
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4answers
496 views

Why is the IP layer aware of higher layers in the network stack?

In the IP packet header there is an 8-bit Protocol field (at offset 9) that holds the "next level protocol", with assigned numbers given in RFC 790. For example, TCP is 6. My question is, why is the ...
2
votes
1answer
100 views

Why does Neighbor Discovery Protocol have to monitor upper-layer protocols?

While reading the RFC of NDP I wondered, why it is necessary to monitor upper layer traffic in order to know if a neighbor is reachable, e.g. a TCP ACK. I do get the IPv6 packet anyway, so I know it'...
1
vote
1answer
2k views

Inter VLAN with layer 2 and 3 switch

Is there a way to interconnect VLANs using this diagram? MLS0 has this configuration: interface FastEthernet0/1 switchport trunk encapsulation dot1q switchport mode trunk And SW0: interface ...
1
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3answers
1k views

HSRP Issue Both sides are active ( Layer 3 4300 X serires)

Why does HSRP shows both sides are active HSRP? Could you please give me details answer? First router: **Vlan111 - Group 6** State is Active 5 state changes, last state change 2w4d Virtual ...
1
vote
1answer
2k views

Can't ping through L3 switch

I've built a scenario in Packet Tracer that I am looking at implementing but having issues with pinging from a PC through a L3 switch. From the switch, I can ping every IP address in the environment ...
3
votes
1answer
10k 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 ...
0
votes
2answers
16k 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 ...
1
vote
2answers
325 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 ...