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Questions tagged [linux]

For questions about or involving the open-source operating system modelled on UNIX. Use this tag only when your question is about Computer Networking where Linux is used as a network device.

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16 views

openVPN client connects to VPN server from Android app but not from Ubuntu or iOS app [on hold]

Disclaimer: I am posting with full knowledge that the school owns the network and has every right to restrict traffic as they wish. My rpi3 is running an openVPN server configured using PiVPN and it'...
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0answers
16 views

IPFIX Flows from OVS Linux Bridge are not accurate [closed]

I’m struggling to understand my IPFIX flow data. To explain: I have an Ubuntu (16.04.2 LTS Xenial Xerus) box, and within that box, I have a single Linux bridge: root@Ubuntu1:~# ovs-vsctl show ...
3
votes
0answers
30 views

Why does TCP exit out of slow-start faster than expected?

For context, I am testing a client-server TCP flow, where the client makes a request for a file, and the server sends the file using regular TCP streams. Both servers are using the "Cubic" ...
2
votes
1answer
52 views

Virtual IP failover issue with vmware exsi ip based hashing

We are deploying HA database cluster on exsi which based on virtual IP concept for failover. if One node fail reserved VIP will be assigned to another node we have two exsi nodes and two virtual ...
0
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1answer
34 views

Access Localhost (Ubuntu -VM) from Windows [closed]

I use Ubuntu in my virtual machine and start from there my code projects. These project when active can be run under localhost:3000. Now when i execute in Ubuntu ifconfig I get following result: If ...
0
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0answers
64 views

Mininet - Configure an IPv6 Router

There are a handful of examples for adding an IPv4 Router in a mininet topology. What there are almost no examples of, is how to add an IPv6 Router in a topology. I have read a few posts on the ...
0
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0answers
21 views

Reduce Packet Tracer window size

I downloaded Packet Tracer 7.2 for my Linux Mint machine. At first everything worked. But now it looks like this: The interface is way too big. Does anyone know how can I reduce the size of it?
1
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1answer
85 views

How can I configure link aggregation/bonded LAN for my simple Ubuntu router build? [closed]

I'm spinning out on this one...! Someone please help! I followed this fab tutorial below to make my own Ubuntu based router: How to build a simple router Ubuntu Server 18.04 Which works great using ...
1
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1answer
48 views

Which layer and protocol takes care of power-down and power-up of ethernet port

Which layer and protocol takes care of power-down and power-up of ethernet port (based on cable connected or disconnected) in a Linux machine. I think it (power-up and power-down) will be taken care ...
0
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1answer
55 views

How to get MAC address on same sub-network without IP [closed]

Currently I am working on a research project, let's say we have two computers connected over LAN cable directly with out any switch or router in same sub-network. Both nodes not have IP address ...
0
votes
1answer
23 views

Daisy chaining IOT devices without switches? [closed]

I have multiple IoT board with two network interface in each device. I want to connect them in a daisy chain without help of switch. The eth1 of first device will be connected to eth0 of second device,...
0
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1answer
36 views

How do I find the IP of the DNS server that respond for a specific domain name?

So as the title says I want to get the IP of the DNS server that respond when I'm trying to reach a specific domain, using bash commands. If I understood it right, when I'm trying to reach www....
0
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1answer
43 views

Linux network bonding/teaming

I have two linux servers with two NICs each and two unmanaged switches. This is my preferred design: Server A - eth0 -> Switch 1 Server A - eth1 -> Switch 2 Server B - eth0 -> Switch 1 ...
1
vote
1answer
140 views

Understanding IP multicast in linux [closed]

My ultimate goal is to setup IGMP snooping on a linux machine using netfilter hooks. This is for exploratory purposes to understand IGMP protocol. The topology we are using is as follows: | ...
1
vote
1answer
425 views

Can I force a higher TCP segment size with netcat?

I'm using netcat to send random data from A to B, both Linux machines on Ethernet networks, with a router in the middle. For pedagogic purposes I'd like to force IP fragmentation on the router (Cisco ...
-1
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1answer
195 views

Can't save configration in router(gns3 )

I have installed gns3 v2.1.9 with gns3 vm(oracle v5.2.18) in my Ubuntu 64bit v18.04. I have installed 2 routers 3725 and 3745 in gns3 vm. But if i try to save my config with copy running-...
4
votes
1answer
349 views

Linux TCP stack repeatedly sends “TCP window update” without acknowledging any data

My company is developing its own TCP stack for low-latency purposes and one of the tests involves running 128 instances of ncat on Linux 4.11 to listen to ports 55000 through 55127 and sending data in ...
1
vote
2answers
574 views

How to connect Cisco Catalyst 2960G using a RJ45 Console Port

Got a used Cisco Catalyst 2960G-24TC-L switch for studying networking and having a fundamental issue. As I new to networking, I'm trying to figure out what type of cable I need to use for connecting ...
0
votes
1answer
2k views

“ssh: connect to host myserver port 22: Invalid argument” (intermittent, ipv6, link-local address, dhcp hostname) [closed]

Since this question is off-topic I moved it to Super User. But I was unable to delete it. Here is the new location. Here is the original question: I'm trying to connect to a headless server via my ...
2
votes
2answers
726 views

GRE-IPsec Tunnel between Cisco Router and a Linux Router

I am trying to create a GRE/IPsec tunnel between Cisco router and a Linux Router. The tunnel is UP and active, but when I do a "show crypto session" on the Cisco router the Active SA's keep on ...
1
vote
1answer
109 views

Improve ping speed (lower up ping time) [closed]

In normal network with Cisco 3650 (1Gbps) and Linux base servers, the ping time is between 0.150ms to 0.250ms. (I also mean using ping or ICMP is to refer to all protocols) I want to know is there ...
4
votes
2answers
3k views

Cisco Nexus vPC LACP bonding with server issue

I am configuring vPC end to end till my server to get more bandwidth, and following is my scenario I am seeing one strange thing which is i configured vPC on N3k switch and then i configured my ...
0
votes
1answer
308 views

Wireshark capture on LoopBack interface [closed]

We have two applications running on same machine, both of them are listening on the loopback interface on two different ports. Client Application is sending data to server, but receiving Application ...
0
votes
1answer
201 views

Accessing Servers behind double NAT [closed]

Basically, I want to know every possible way to access Linux servers or any other devices located behind ISP'S (Carrier-grade NAT) and our local NAT. I have used VPN and forward-reverse tunneling ...
6
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2answers
357 views

how to find the right value of MTU Jumbo frame

we take the decision to set jumbo frame on all our linux machines we have hadoop cluster with master machines , workers machines and kafka machines our switches ( Cisco ) are suitable to Jumbo frame ...
1
vote
1answer
178 views

tcp sequence number and routing rule

I'm doing a network project. I first create a tcp socket, which is a merely a placeholder. Then I send tcp many packets by libnet. ISN is captured through tcp 3-way handshake and seq number after is ...
0
votes
1answer
4k views

Confused about Linux “route add” commands for this diagram [closed]

I am confused about this network diagram. In class the router R1 was assigned to me and other students were given various routers/workstations on the diagram. Our task was to set the network up with ...
0
votes
1answer
701 views

What will happen at server side if it received 2 SYN packet from the same client application?

A server moves to SYN_RECV state once it gets a SYN packet from a client application. What will happen at server side if it received 2 SYN packet from the same client application?
0
votes
1answer
81 views

How to get Adtran TA5000 23 firmware information with an SNMP request?

I'm looking for any SNMP request that I could use through a Linux terminal to get the firmware information of all our ADTRAN DSLAMs that we currently have in the field(there are close to 18,000). I ...
0
votes
1answer
496 views

What could cause kvm virtualized pfsense to get 84mbps behind physical pfsense, but then drop to 1mbps when it replaces physical pfsense?

I'm scratching my head on what could cause the following behavior: Scenario A: Laptop -> virtualizedpfsense -> switch -> physicalpfsense -> modem speedtest.com gives me 84mbps download (...
2
votes
1answer
619 views

MPLS over GRE tunnel with Linux iproute2 [closed]

I'm trying to encapsulate IP packets in MPLS, transported over a GRE tunnel between two Linux hosts (a and b). a has 10.199.0.1 on GRE tunnel interface foo4, while b has 10.199.0.2 on GRE tunnel ...
2
votes
1answer
311 views

ARP flush manual broadcast after IP change

This is strange requirement but thought let me ask if some has good advice, so we have Linux iptables firewall with 3 interface, public, Internal and DMZ now we decided to replace linux firewall with ...
0
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1answer
94 views

Different results when same WireShark pcap file opened in Unbuntu17.04 and later Windows 10

Using Ubertooth, a bluetooth sniffer, I created a pcap file in Unbuntu that captured some data. When I opened that file in WireShark 2.4.1 in Windows 10 it showed more information in the SMP data ...
3
votes
1answer
3k views

net-snmp Creating my own MIB: No Such Instance currently exists at this OID [closed]

First thing first. I want to create my own MIB. Please pardon me if I'm asking a simple question as I'm a newbie to SNMP and I'm struggling on this from couple of weeks. I have already been through ...
1
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2answers
51 views

Can i use an actual network management application and connect it to a router inside GNS3?

I want to connect a NMS to a router on GNS if it's possible, so that i can practice the "actual thing".
1
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1answer
111 views

Why I don't see drops with a TCP flows in Linux

I wanted to observe the congestion window of a TCP flow so for that I have to nodes (using Linux namespaces) connected to each other through veth pairs and a bridge. To limit bandwidth to 10mbps I ...
2
votes
1answer
379 views

GNS3 v2 router to host connection

I'm trying to make a router inside GNS3 to connect to the host device (a Debian 8) with no success. Am I missing something? DHCP works as expected: ! interface FastEthernet0/0 ip address dhcp ...
2
votes
3answers
208 views

How does Ethernet driver know if the cable is plugged in?

How does the /sys/class/net/ethx/carrier field get set? I am trying to understand this field as it determines if a network cable is plugged in, but I am curious how it knows. This is specifically in ...
0
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1answer
380 views

Linux LACP (802.3ad) working for ingress traffic only?

We've setup LACP (802.3ad) on our Juniper switch and a Linux host, connected to the switch with 3x 1Gbps links. We are able to download from multiple sources at a rate of 3 Gbps, but when uploading ...
1
vote
2answers
259 views

How do I determine the IPV6 address added to VXLAN when interface is set to up? [closed]

Setup: Currently working on a machine with Red Hat 7.2 (Red Hat Enterprise Linux Server release 7.2 (Maipo) to be exact.) I have a vxlan interface configured: # ip link add test.123 type vxlan dev ...
3
votes
0answers
689 views

Is IKEv2 remote access VPN possible to an ASA 5510 without Cisco AnyConnect as the client?

I'm trying to configure a remote acccess vpn into a cisco ASA 5510 (9.1(7)15). I want to be able to use IKEv2 with Certificate + user/password xauth with strongswan as the client under Ubuntu. I ...
2
votes
1answer
413 views

TC & Qdisc Rules with 'Leaf' classes [closed]

I'm trying to determine a class which would be used as default for new IP's on my network, here's my current setup: # Delete qdisc rule tc qdisc del dev br-lan root # Add qdisc rule tc qdisc add dev ...
1
vote
1answer
164 views

Is it possible to control data length inside tcp frame? [closed]

I have a two different CUPS installation. One is 2.2.0 runs on macOS (10.12.2) Another one is 1.6.3 runs on Linux minibian 4.1.7-v7+ ( Raspberry ) There is thermal printer connected via network and ...
4
votes
2answers
428 views

SNMP agent on embedded device, No such object available on this agent at this OID

SNMP agent on an embedded device. When I query SNMP device for the particular private enterprise OID object, it says "No such object available on this agent at this OID". snmpget -v2c -c public 10.x....
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votes
2answers
121 views

Wireshark can't capture packets from machine 2 to machine 3

I got an idea there were 3 machines. machine 1,2 amd 3. Machine 2 ping to machine 1, i can capture the packets by using tcpdump. But mchine 2 ping to machine 3 , then machine 1 can't capture by using ...
2
votes
1answer
116 views

Different between VLAN broadcast behavior on a Cisco switch and a Linux bridge

When will a packet be tagged/untagged with a VLAN tag in these cases: On a Cisco switch On a 8021q subinterface in Linux (for example, eth0.10) On VMWare ESXi (with VLAN ID in VMNetwork setting) ...
0
votes
1answer
285 views

What does limit a MTU set for an interface? [closed]

The maximum MTU I can set is between 9000 an 10,000 for a Ethernet interface. I have the following message for high values ifconfig eth0 mtu 10000 SIOCSIFMTU: Invalid argument What is the origin ...
1
vote
1answer
223 views

How to copy running-config on the cisco switch

i would like to ask how can i copy running-config from my switch to linux, and a ready configurations (with changed values) back to switch but i dont want to use any ftp server or any other method ...
1
vote
0answers
2k views

Tunnelling difference over VXLAN vs NVGRE vs GENEVE [closed]

Any bullet points that are most imp points when it comes differences between these three tunnellings VXLAN/NVGRE/GENEVE in networks. Found some notes here, anything that you may like to add would be ...
0
votes
1answer
95 views

linux network card packet timestamping [closed]

Curious to know an application that uses hardware time-stamping presented in network cards. If you know any app uses this please list down here. I saw people writing application through UDP sockets ...