Browsing articles tagged with "networking - 10/252 - Admins Goodies"
Jul 30, 2012
tom

ESXi server under DoS attack, can I use SSH to determine where from?

My VMWare ESXi 4 server appears to be under a Denial of Service attack. I am getting massive packet loss to the server (60+%) and am barely able to load any services on the VMs running on the host. I have Cacti installed but cannot load it due to the attack. I can SSH in to the VMware host. Are there any commends I can run to either determine where the attack is coming from, […]

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Jul 29, 2012
tom

Can i configure the tcp SYN retransmission interval?

As far as I know SYN retransmissions: with rounding they occur 1, 3, 6, 12, 24, 48, and then 64 seconds apart. I want to do this on different interval time. what is the name of this parameter? can I control on it in android and windows? Asked by user1495181 Windows: You can only control the first retransmission with HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters\Interfaces\ID. After this, the retransmitted SYN packets are dynamically controlled (Source: KB 170359) Edit: Per discussion […]

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Jul 24, 2012
tom

Why couldn’t MAC addresses be used instead of IPv4|6 for networking?

I am reading up on TCP/IP and other related protocols and technologies. MAC addresses are described as being (reasonably unique, and as having a large possibility space (several hundred trillions), while also being assigned to all network interfaces. What are the historical and technical reasons why IPv4 or IPv6 addresses are used instead of MAC addresses for internetwork communication? Am I missing something fundamental or is it just a silly reason (e.g. building on top […]

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Jul 21, 2012
tom

How do i create a ‘layer’ in between my router and a user connecting to it

Like when you go to starbucks the first thing you see if you go to their wifi is “Welcome to starbucks, please accept our terms”. Or also at most airports, it makes it impossible to surf until you accept their terms. Furthermore, what is this called? Is it possible to order routers with this pre-loaded on it, and how would I go about this? Asked by Tallboy The term for what you want is “captive […]

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Jul 21, 2012
tom

How to bridge a range of public IPs to KVM virtual machines on Debian/Ubuntu

I’ve been trying for weeks to figure out the right network configurtion for sharing a range of public IPs with KVM virtual machines running on my server, but so far with little luck and with the help of the friendly ServerFault community, I’ve managed to make it work. You can find my working setup below: My ISP routes all the traffic to 192.168.8.118 (so that needs to be the primary IP of eth0), but I […]

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Jul 20, 2012
tom

How do I setup a NIC for outgoing connections and the other to serve my Squid proxy?

I have an internal network (192.168.2.0/24) that I’m supposed to connect to a proxy. I’ve already installed and test(with a little traffic) an Squid 3 cache/proxy server in a Ubuntu 12.04 box with this IP address: 192.168.2.102 eth0. Also, I have another physical NIC with IP 192.168.2.101 eth1. The setup that I’ve done consists in the Ubuntu box going out to internet and serving the Squid in the same eth0 NIC. I have the concern […]

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Jul 19, 2012
tom

Cheap way to detect client round trip times for http

I am trying to figure out a way to detect round trip times for each IP that connects to port 80 on my server. What is a good way to do this? There are far to many connections, and pinging each ip is not practical. I was thinking, somehow measuring the time difference between when server send the syn/ack packet and when server receives the ack for it. Is there a way to log this […]

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Jul 18, 2012
tom

How would I restart network services without restarting the server?

I’ve been an IT professional for county government over 2 1/2 years and this problem has occurred 3 times. I can fix it by restarting the primary server, but I would like to fix it without having to take that route. Here’s the situation. On our primary server (from here on out called Server1) we have software running called Springbrook (fund accounting and utility billing enterprise software). The users access Springbrook via mapped drives to […]

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Jul 16, 2012
tom

Terrible ping times between wireless / wired subnets

I have a SonicWall router configured as follows: P0 = Wired LAN (192.168.1.1) P1 = Internet P3 = Sonicpoint WAP (192.168.5.1) P3-A = Private Wireless LAN VLAN 1 (192.168.6.1) P3-B = Public Wireless LAB VLAN 2 (192.168.7.1) If a computer is on P3-A their IP address would be 192.168.6.2 and their gateway would be 192.168.5.1 If I ping any internet site (google.com) I get sub 30ms responses. If I ping an address on P0 (192.168.1.4), […]

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Jul 13, 2012
tom

Setting up an Office Network

I’ve recently moved in to a new office who gets its internet through wired ports dotted around the room. I want to move them wireless but want to check which equipment would be useful before I start spending money! If I buy a high-quality wireless router, can I plug the internet directly in to it and share it amongst everyone in the office? With the same router allow access to a printer plugged in to […]

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