Newest Questions
17,015 questions
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Chrome complains about self-signed certificate on Windows [closed]
My goal is to add SSL certificates to my local network services. So I´ve generated a self-signed CA:
openssl req -new -newkey rsa:4096 -days 3650 -nodes -x509 -subj "/C=.../CN=LAN ..." -...
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3
votes
2
answers
324
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Can I perform inter-VLAN routing on a Layer 3 switch using a single trunk cable connected to an unmanaged Layer 2 switch?
My scenario: I have many endpoints currently connected to an unmanaged switch. I want to add Layer 3 switch and segment the network into VLANs, but I'd like to avoid the manual work of tracing which ...
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0
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14
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Why my home internet is frequently disconnected, but university internet has 100% uptime? [closed]
It is a cliche that no internet has 100% uptime. I've been in university for several years and never experience one disconnection.
However, home internet can be unstable. If I pay for a high-end 1000m ...
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0
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25
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Does it make sense to put a router into Bridge mode for the purposes of using it with a hardware firewall? [closed]
I have a fiberbox and a router.
I want to put a hardware firewall in between the two, but when I power on the firewall, it doesn't have any WAN address, presumably because the modem isn't assigning it ...
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0
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25
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'User role not defined...' error showing while authenticating against AD in packetfence [closed]
whenever I'm testing any AD user authentication, showing 'user role not defined...' error in radius logs. I have already created role and configured in authentication source but still not working. I'm ...
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0
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20
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Is it possible that POE on a UTP link increases resistance to interference? [closed]
This comment on https://diy.stackexchange.com/questions/326245/will-this-cat6-cable-be-too-close-to-the-120v-electrical-wiring got me wondering...
If you have issues with noise on your Cat6, add a ...
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1
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0
answers
42
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FRR BGP peering on ipv6 link-local address
I have following setup in my lab. Host1/2 running ubuntu with FRR daemon for BGP. R1 is my cisco nexus switch. I want to route traffic between host1 to host2.
[host1]------ibgp----[R1]------ibgp----[...
- 4,461
0
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1
answer
26
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how does anycast network deployment work?
as far as i understand, anycast network i.e a /24 block is announced by a BGP with the same ASN from multiple regions. anycast networks such as 1.1.1.1 and 1.0.0.1 are largely used for DNS services or ...
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0
votes
1
answer
29
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ACL on router originated traffic
For router originated traffic for example routing protocol hello packet that source from the local router.
Do ACL have any effect on them ?
I remember that in some Old CCNA study materials, it stated ...
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12
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Looking for a Network Architect/Engineer in London [closed]
Network Designer – London or Ipswich – Permanent (37 hours per week) – DV Clearance or willing to undergo
Our client is supporting the Defence and National Security industry and are looking for a ...
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2
votes
1
answer
117
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Counting to infinity in distance vector routing problem
Slides are taken from: https://cseweb.ucsd.edu/classes/sp15/cse123-a/lectures/123sp15-lec15.pdf
When converged and just after B-C link breaks(and when B knows that B-C does not exist anymore), the ...
- 123
3
votes
2
answers
136
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Cisco Catalyst Switch 2960X Gibberish Console Output
I bought a 2nd hand Cisco Catalyst switch for a cheap price I tried to connect to it using the RJ45 port - USB port, I used putty to connect to the console at first I ran everything normal 9600 baud ...
- 31
1
vote
1
answer
178
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Dell EMC Switch to Juniper EX2300 Switch
I'm fairly new so this might be a simple question, but haven't had any luck when trying to Google them.
I'm trying to get a Dell N2224PX-ON switch to communicate with a Juniper EX2200 switch via ...
4
votes
1
answer
549
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Switch internal layout
Tanenbaum's Computer Networks book has nice schematic drawings of hubs vs switches.
I wonder why he draws a full grid for the switch. In my understanding the green stuff (my addition) would be enough?
...
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1
vote
1
answer
152
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If the router is a Layer 3 device, does it even support Layer 2 forwarding (like a switch does)?
Nowadays we have multilayer switch and pure layer 3 device.
Do "pure" layer 3 device like a router use layer 2 protocol ?
Do they require layer 2 header to operate ?
If so, what are the ...
- 165
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1
answer
31
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Question on lldp chassis ID TLV
I have a question regarding lldp chassis ID LLDP TLV. If your switches are in a stacking or virtual switching setup, the lldp chassis ID TLV from slave/standby units will be its own chassis MAC ...
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0
answers
50
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1st time Firmware update
Im a junior networkengineer and my first job is to upgrade remotly the firmware of the 2960X-24PS-L switch from c2960x-universalk9-mz.152-7.E7.bin to c2960x-universalk9-mz.152-7.E12.bin.
How to do ...
3
votes
1
answer
1k
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Why do we still need NAT pool network mask when we already have starting IP and ending IP?
When configuring source NAT in cisco device
for the command that create nat pool
ip nat pool MYPOOL 203.0.113.10 203.0.113.20 netmask 255.255.255.0
Why do we still need NAT pool network mask when we ...
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4
votes
1
answer
616
views
Wasn't separation of traffic between bridge ports problematic in the presence of hubs?
I know hubs are a thing of the past, but I'd like to know if my reasoning is correct and accurately describes how things worked 30+ years ago. Assume we have a classic two-port bridge, a hub connected ...
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7
votes
1
answer
1k
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Server does not send FIN ACK response, but instead ACK with "out of range" Ack number increased by 1 byte
We are trying to track down some very strange behavior with IBM MQ managers. To keep the intro short and high-level, MQ clients subscribe to durable subscriptions on those MQ managers (all affected ...
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1
vote
1
answer
194
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Large (traceroute) SYN packets dropped in IPv4
I've been running a few TCP-traceroutes towards some target and noticed that larger SYN packets (say, >5B TCP payload) are dropped. But only in IPv4. In IPv6 those are still delivered.
I also ran ...
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0
answers
22
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Unexpected UE Behavior
We recently observed an interesting issue during LTE testing:
The eNodeB transmitted only a UL grant (DCI 0) for a UE — there was no DL grant intended for that UE in the same subframe.
On the UE side, ...
2
votes
1
answer
585
views
Why does TCP have a dedicated Window Size field while HDLC doesn't?
Both TCP and HDLC implement flow control mechanisms. Both protocols have dedicated fields for Sequence Number and Acknowledgment Number.
However, TCP includes a dedicated Window Size field in its ...
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4
votes
2
answers
248
views
Do routers rate-limit TimeExceeded packets generated by other routers?
I know routers often rate limit the generation of ICMP error messages to keep CPU load managable.
Does anyone know if there are routers that also rate limit the forwarding of ICMP messages? In ...
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0
votes
1
answer
40
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If I generate BOOTP/DHCP xid, can it be an unique (MAC based) number but constant?
If I'm a client and I generate XID using condensed version of a MAC address (chaddr) to ensure unique 4 byte transaction ID, does that pass RFC951 specs? Aside that it has to be a random number to ...
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3
votes
0
answers
51
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Why Do We Need Advanced OTN Features When MPLS-TP or Similar Packet Transport Technologies Exist?
As a service provider, suppose all customers only need Ethernet services (L2 or L3 VPN). In that case, why is an OTN layer necessary? Wouldn’t a simple physical layer infrastructure—such as optical ...
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1
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60
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How to set up IPsec for pfSense with load balancer in front that provides private IP addresses?
I’m trying to set up a network with the following configuration:
My load balancer is a TPlink - E3707-M2
The challenge I’m facing is that pfSense requires a WAN interface with a public IP, but the ...
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0
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2
answers
60
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Invalid input on 7th Etherchannel and above in PacketTracer
Good evening -
I am setting up a network in Packet Tracer and I'm not sure why I am getting this error.
The setup:
I have 5 edge switches representing 5 floors of an office. I want to connect an ...
3
votes
1
answer
70
views
Did ipv6 ever solve the issue of opening listening ports at CPE or beyond a carrier-grade NAT router that is not owned or controlled by the user?
Stupid question I know. I guess I'll just stick with ipv4 for another 20 years and not bother with ipv6. But.....
Let's say your dual stack net connection does not come with a public IP so to speak. ...
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0
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2
answers
51
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why does FDM uses bandwidth bands in practice
I am reading Tanenbaum's Computer Networks. Section on FDM left me confused.
In FDM, a carrier frequency is modulated via amplitude, phase or frequency to transmit signal - typically amplitude and ...
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3
votes
1
answer
78
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Firewall Security Policy for traffic that destined to / originate from the firewall
I was trying to set up a IPsec tunnel on the firewall.
I wonder how do firewall handles the traffic that destined to / originate from the firewall ?
Since Interface Profile do not have a option to ...
- 165
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0
answers
42
views
Bit Ordering in Bluetooth Low Energy (BLE) Link Layer Packets
As part of a project, I am trying to simulate the link layer packet generation of the Bluetooth Low Energy (BLE) standard version 5.4, with the specification found here. What's relevant to my current ...
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1
vote
2
answers
84
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Practical importance of bonding and grounding Ethernet cables in IP camera installations
this is my first post in this community. I’m looking forward to learning from your expertise.
I’ve noticed that many IP camera installers skip proper bonding and grounding when connecting cameras to ...
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2
votes
1
answer
96
views
Why would nmap show a port open on an unused IP address?
I work with NAC in my job, and one thing we're noticing is that every endpoint, regardless of what device type it is, shows up as having 1720/TCP open. When I log into the CLI of our NAC appliance and ...
0
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0
answers
73
views
LibreNMS maps > network - Link types of LLDP are not supported
I installed LibreNMS and added six devices. The LLDP protocol is enabled on the devices, and data is being sent from them without any problems. However, I can’t see the neighborhood map. The map tab ...
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6
votes
1
answer
594
views
How does a multirate SFP work?
I was recently looking into Ethernet fiber standards and auto-negotiation, and I stumbled upon "multirate SFP transceivers".
At my current employer, we use networking equipment that supports ...
- 435
0
votes
1
answer
89
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NAT applied but no NAT test policy match
On the Palo Alto firewall traffic log, there is a traffic that has NAT Applied
But when I try to test policy match, I cannot find such a NAT POLICY. I even tried to test policy match in the opposite ...
- 165
5
votes
3
answers
1k
views
Unknown MAC address data frame flooding by switch
Let's say switch A has 2 switches connected at port 2 & port 4. There are a total of 8 ports.
With time, it knows the MAC address of other devices connected to it.
Now, the device on port 1 wants ...
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1
vote
0
answers
81
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Enabling inband SSH on Nokia 7250 IXR-e TiMOS-C-24.10
How to enable Inband SSH on a Nokia 7250 IXR-e with TiMOS-C-24.10?
The device can only be reached through the management interface, but not with inband IP, even if they are reachable.
I cannot find in ...
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1
answer
57
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OPNSense Schedule is not working no matter where I place it
I try to place a schedule in OPNsense for one of my VLAN interfaces to shut down between 10 PM and 5 AM. However, when I try to enable it on my firewall, it blocks the whole internet, even if it isn't ...
3
votes
5
answers
1k
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In "Computer Networks:A Top Down Approach" - can multiple applications using the same protocol use its designated port?
I am reading "Computer Networks: A Top-Down Approach," edition 8. On page 153, it says:
Recall also that when a client or server program implements a protocol defined by an RFC, it should ...
4
votes
5
answers
1k
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In a network operating on layer 3 of the OSI model, why is the destination MAC address needed if the target host is in another network?
I am studying the OSI Model, and to my understanding: a MAC address is needed to transmit a message to a node within the same physical network or to a switch/router. IP addresses are used for globally ...
1
vote
1
answer
87
views
AS number used in EIGRP
What AS number range should be used in EIGRP ?
Public vs. Private ASN Ranges
ASN Type
16-Bit Range
32-Bit Range
Notes
Public ASNs
1 – 64511
1 – 4294967294
Globally unique; used for Internet peering ...
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1
vote
3
answers
153
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What bottleneck/factor decides the MTU for a network?
I don't mean calculating minimum MTU along a path.
I mean, what factors determine how large an MTU can be at all? Is there a physical bottleneck of some sort? For example MTU for the Internet is 1500 ...
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2
votes
1
answer
270
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Why does every TCP state diagram omit SYN SENT receiving a RST?
I am writing a TCP state machine, and I am trying to find an exhaustive state diagram.
After the handshake is initiated with SYN, I assume it's possible that the server rejects this? And I assume they ...
- 123
0
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1
answer
111
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Vlan on Stormshield PB
I'm coming to this forum because after a lot of research and testing, I'm unable to set up a VLAN solution on a Stormshield SN 510. Regarding my infrastructure, a router providing internet access and ...
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0
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1
answer
71
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Clear Channel Assesment ( CCA in wifi)
I have been learning about the WLAN technology, and I couldn't understand the logic behind the choice of the Clear Channel Assessment thresholds protocol used.
I'm trying to understand the logic ...
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0
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0
answers
52
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SVI Migration to the Fabric cisco
Can someone briefly explain how the SVI is migrated from a switch to the Fabric.
Thanks
0
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0
answers
46
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Conditional handover comparison with baseline handover in 5G
While implementing baseline handover in 5G and conditional handover, I found that the implementation will not lead to any significant differences between the two handover schemes. Does anyone else ...
4
votes
5
answers
2k
views
Need Advice - 140m Ethernet Run Between Buildings
I'm facing a technical challenge and could really use your expertise. I need to establish a wired network connection between two points 140 meters apart - well beyond the standard 100m limit for ...
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