Questions tagged [linux-networking]
Linux Networking refers to any networking function performed by a server running Linux. A Linux server operating as a router or firewall are the most common applications.
167
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Adding a whole IPv6 /64 block to an network interface on debian
I tried adding a whole IPv6 (/64) block to an interface using
ip route add local 2001:41d0:2:ad64::/64 dev lo
like described here on my Debian server, but I seem to be missing something.
If I ping ...
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42
votes
2
answers
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How to reduce number of sockets in TIME_WAIT?
Ubuntu Server 10.04.1 x86
I've got a machine with a FCGI HTTP service behind nginx, that serves a lot of small HTTP requests to a lot of different clients. (About 230 requests per second in the peak ...
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26
votes
4
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Linux e1000e (Intel networking driver) problems galore, where do I start?
I'm currently having a major problem with e1000e (not working at all) in Ubuntu Maverick (1.0.2-k4), after resume I'm getting a lot of stuff in dmesg:
[ 9085.820197] e1000e 0000:02:00.0: PCI INT A ...
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1
answer
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How to troubleshoot latency between 2 linux hosts
The latency between 2 linux hosts is about .23ms. They are connected by one switch. Ping & Wireshark confirm the latency number.
But, i dont have any visibility into what is causing this latency. ...
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65
votes
6
answers
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Hostnames - What are they all about?
I've recently been "forced" to perform some sysadmin work, while this isn't something that I absolutely love doing I've been reading, experimenting and learning a lot.
There is one fundamental aspect ...
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32
votes
8
answers
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how to find out mac addresses of all machines on network
Is there some easy way to find out mac address of all machines on my network rather than doing an SSH into each and ifconfig | grep HWaddr if there are 300 machines on network I really need some easy ...
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10
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4
answers
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AWS VPC + IPtables + NAT: Port Forwarding is not working
Yesterday, I posted a question here but I think was not clear enough in my words. BTW, This question is not a duplicate.
I have AWS VPC Setup as below.
GOAL/PROBLEM: SSH to Server A from internet. ...
- 504
6
votes
3
answers
25k
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Delete specific conntrack entries?
in a multi-ISP configuration, I'm routing and NATing specific traffic, e.g. VoIP, through specific interface - to a distinct provider.
When one of the interfaces (or routes) becomes unavailable, all ...
- 607
6
votes
3
answers
38k
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How to set up two default routes in linux
TL;DR
How to set up two default routes in linux (corresponding to two interfaces), such that incoming traffic from both interfaces is accepted.
Scenario
I have a host having two NICs eth0 and eth1....
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4
votes
1
answer
3k
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stunnel: SSL-to-SSL? (for smtp/imap)
How can I configure stunnel to accpet SSL connections, and connect then to an SSL port on a different server?
Here is my setup:
Our ISP's server, "Mail Server", supports smtp/imap over SSL. (Not ...
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2
votes
2
answers
12k
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Simple client / server with nc not working
Why is the following not working?
I have a freshly installed Debian 9 system. iptables is wide-open:
[···]# iptables -L
Chain INPUT (policy ACCEPT)
target prot opt source ...
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-1
votes
2
answers
11k
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Postfix - How to prevent external clients from using my server as a relay? [closed]
I have a postfix server installed on Ubuntu 14.04. A PHP script running on the machine uses it to send outgoing email. Additionally, I use postfix to receive mail sent to a local account, which is ...
- 31
50
votes
2
answers
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iptables and multiple ports
This doesn't work for me:
# iptables -A INPUT -p tcp --dports 110,143,993,995 -j ACCEPT
iptables v1.4.7: unknown option `--dports'
Try `iptables -h' or 'iptables --help' for more information.
...
- 938
25
votes
4
answers
68k
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multiple MAC addresses on one physical network interface (linux)
Simple question:
How can I setup multiple MAC addresses on one physical network interface (linux)?
Why?
My ISP is checking ip<->mac on GW and I d like to route traffic through my "linuxbox" and ...
- 253
20
votes
2
answers
53k
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SSH: DH_GEX group out of range
We recently applied a vendor-supplied patch for OpenSSH. This patch disabled a few key exchange protocols in response to the recent Logjam attack. After applying this patch, we have a few vendors ...
- 301
18
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4
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115k
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"Stale NFS file handle" after reboot
On the server node, it is possible to access an exported folder. However, after reboots (both server and client), the folder is no longer accessible from the clients.
On server
# ls /data
Folder1
...
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18
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3
answers
103k
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How to set a static IP (client side) in OpenVPN?
I am setting up a VPN network with a lot of little devices (running OpenWRT). In my use case, the devices are all identified by a number and I would like their ip adresses to match their ID (e.g: the ...
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16
votes
1
answer
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VLAN tags not shown in packet capture (Linux) via tcpdump
I am adding a tagged VLAN onto eth0:
#ip link add link eth0 name eth0.20 type vlan id 20
This results in:
#ip link
2: eth0: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast ...
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12
votes
2
answers
41k
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DH GEX group out of range
I'm having a sudden issue SSHing into my server:
ssh -v --@--
OpenSSH_7.2p2 Ubuntu-4ubuntu1, OpenSSL 1.0.2g-fips 1 Mar 2016
debug1: Reading configuration data /home/paul/.ssh/config
debug1: Reading ...
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12
votes
5
answers
7k
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tc u32 --- how to match L2 protocols in recent kernels?
I have a nice shaper, with hashed filtering, built at a linux bridge. In short, br0 connects external and internal physical interfaces, VLAN tagged packets are bridged "transparently" (I ...
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12
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1
answer
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NAPI vs Adaptive Interrupts
Could anyone please explain how two following technologies are used to mitigate interrupt overhead under high networking load?
Adaptive-rx/Adaptive-tx, and
NAPI;
I would appreciate an answer that ...
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10
votes
1
answer
18k
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Why does Linux answer to ARP on incorrect interfaces?
I have the following Linux networking setup: there is an eth10 network interface with the assigned address 10.11.0.1/24. Then there is a tap0 network interface with assigned dummy address 0.0.0.1/32 (...
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10
votes
4
answers
11k
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Is it possible to enable port isolation on Linux bridges?
On most managed switches you can enable Layer 2 Port Isolation. The implementation and terminology is different from vendor to vendor but generally speaking you keep one or more ports in the default ...
- 445
7
votes
5
answers
27k
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Can only bring up one of two interfaces
I'm having a bizarre issue with my HP Proliant DL 360 G4p server. It has two gigabit ethernet interfaces but I can bring up only one of them. This is starting to freak me out and that's why I turned ...
- 332
6
votes
2
answers
63k
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openVPN Could not determine IPv4/IPv6 protocol. Using AF_INET
I am having issues connecting to my VPN, with port forwarding set correctly as I can VPN into my other lubuntu machine, also UFW is disabled. Can someone please guide my as to what I am missing in my ...
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votes
4
answers
4k
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Transfer large amount of small files
I've to do a migration of two servers with large SAN attachments to our new VMWare environment.
EDIT: I have to supply some additional intelligence as I have good answers regarding VMWare solution.
...
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5
votes
1
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Linux & IPv6: How to bind to an arbitrary IPv6 address? [duplicate]
Possible Duplicate:
Can I bind a (large) block of addresses to an interface?
I have a /48 IPv6 block. I'd like to be able to do this:
$ wget --bind-address=<1st-ipv6> http://www.some-url....
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3
votes
3
answers
1k
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Iptables rules with ! character
I have entered iptables rules to log a specific connection on our server, but it doesn't seem to be working as I want it to. Here are the rules:
1 LOG tcp -- !10.51.0.0/16 0.0.0.0/...
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3
votes
1
answer
1k
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bonding-rr vs single 10G for NFS NAS - pros and cons?
I'm standing before choice of NICs and switch for storage server and virtualization hosts and I can't decide between 10G and quad gigabit with bonding-rr. 10G is noticeably more expensive solution and ...
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2
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1
answer
3k
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strongSwan ipsec setup, couple of questions
i am trying to setup a IPsec bridge between my home network and my office network. I want to use StrongSwan to encrypt the traffic as IPsec
i am trying to follow this guide
A brief description of ...
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2
votes
1
answer
7k
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Port appears open locally but closed from another machine
I am currently trying to set up a Hadoop distributed compute cluster on my network. Currently. my cluster nodes are encountering a problem communicating with my master server.
Right now I am working ...
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1
vote
1
answer
3k
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bridging two network interfaces in ubuntu linux 12.10 AND being able to access it from that machine
Ok, i have about had it but heres the deal.
I have 7 total machines connected like this:
[5 workstations]<--->ServerPC<---->MAINPC<---->router
FYI, dont worry about the workstations they ...
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1
vote
2
answers
2k
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How can I intercept a socket binding call to map to another port?
Let's assume I have some executable foo and I have bar. Both are hard-coded to listen on port 80. Let's assume we have root.
How can I get both running on different ports? Or one of them? You can ...
- 111
0
votes
1
answer
2k
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How to see if incoming HTTP requests are successful (view the responses) on Linux?
I'm really new to managing servers, and I've discovered that I can run ngrep and see connections from Google to our site (which is currently getting thousands upon thousands of 5xx errors and "crawl ...
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0
votes
2
answers
444
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moving ip of one VM to another VM
I've hosted two VMs on the same machine, one is active in nature i.e. hosting a service and is connected to a client (client is running directly on the host machine).
I've to implement a fault ...
- 121
0
votes
2
answers
3k
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ip routing for extra eni on RHEL ec2 instances
I have noticed that when one add an additional ENI on an ec2, getting routing to work is so difficult and there is no documentation anywhere to refer to.
I do know that if one uses the Amazon Linux ...
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0
votes
1
answer
5k
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Openvpn - enabled redirect gateway but can't access any websites
First of all I'm a newbie to servers but not to stuff like programming so not totally alien to command lines etc.
Second, I want to run openvpn on my remote server and connect from my ubuntu desktop ...
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75
votes
6
answers
216k
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What is the correct way to open a range of ports in iptables
I have come across articles advising for the following:
iptables -A INPUT -p tcp 1000:2000 -j ACCEPT
And others stating that the above will not work and iptables only supports multiple port ...
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54
votes
6
answers
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e1000e Reset adapter unexpectedly / Detected Hardware Unit Hang
I have a Dell 1U Server with Intel(R) Xeon(R) CPU L5420 @ 2.50GHz, 8 cores running Ubuntu Server Kernel Version 3.13.0-32-generic on x86_64. It has dual 1000baseT networking cards. I have it set up to ...
- 2,285
29
votes
1
answer
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What CAN cause 'RTNETLINK answers : No such process' when adding a route
I have come up against this error a number of times, but haven't yet found an explanation of what the error means, or what can cause the problem.
I'm not posting my configs or the specific route I'm ...
- 405
27
votes
11
answers
276k
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Can't start CentOS 7 "network" service
I Can't start CentOS 7 "network" service after disabling and removing "NetworkManager" service.
When I check the network service status, it comes up with the following error:
#systemctl status ...
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26
votes
8
answers
63k
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How to persist ethtool settings through reboot
I would like to turn off tcp segmentation offload on a CentOS5 server. Using ethtool the command is ethtool -K eth0 tso off However, this setting only persists for this session. How can I make it ...
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votes
4
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204k
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Unable to add a static route: SIOADDRT: Network is unreachable
I've been bashing my head against a wall for a few days trying to figure this out:
My ifconfig is:
eth0 Link encap:Ethernet HWaddr 00:50:56:BB:XX:XX
inet addr:192.168.36.132 Bcast:...
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21
votes
2
answers
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Is it possible for L2TP VPN to do auto route configuration for client during connected?
We've setup a L2TP VPN server with this tutorial, everything works like a charm.
The only issue is
We don't want client to route all traffic using this VPN, only a particular subnet, e.g. 10.0.0.0/...
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votes
5
answers
13k
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predictable network interface names in systemd
Recent version of Ubuntu and Debian (stretch) bring a new network interface naming scheme.
Now, when updating from a system that's using old style names like "eth0", I'd like to know prior to booting ...
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16
votes
1
answer
55k
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How GRO (generic receive offload) works on more advanced NICs?
I am interested in particular answers:
Does the NIC with GRO edits/creates TCP ACK or any other packets (or is this feature transparent to receiver/sender TCP stacks)?
There should be a timeout/event ...
- 632
14
votes
3
answers
37k
views
The same IP on multiple interfaces
Hello networking gurus,
I've got a Linux (kernel 3.14) server which acts as a TFTP, NFS and HTTP server for a farm of consumer electronics devices (set-top boxes - STBs). The devices use TFTP to boot ...
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13
votes
2
answers
15k
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PXE Booting Virtualbox guests in internal networking mode?
I am not sure if this is just specific to my distro's packages or is a vbox limitation. So, any help would be appreciated.
Ok, so I have a network of VMs, with one VM acting as a NAT for the other ...
- 486
13
votes
2
answers
47k
views
I need a reverse proxy solution for SSH
Hi here is a situation I have a server in a corporate data center for a project.
I have an SSH access to this machine at port 22.There are some virtual machines running on this server and then at the ...
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13
votes
2
answers
28k
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How to scan ipv6 enabled hosts on my LAN?
I want to discover all my neighbors who enabled ipv6 protocol and still alive. I tried ip -6 neighbor show but it shows nothing.
Can someone recommend a tool and show some examples? Thanks.
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