networking

howto://troubleshoot networks with tracert

2011-01-24

How to use the tracert command to diagnose and troubleshoot networking issues.

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howto://troubleshoot networks with tcping

2010-07-16

A great tool for troubleshooting TCP based connectivity is TCPING.EXE, by Eli Fulkerson. This post goes over how TCP works, and how to use this tool to troubleshoot networks.

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howto://troubleshoot networks with ping

2010-07-09

Call this network troubleshooting 101, where we’ll go over how to use the venerable PING command to do some basic network troubleshooting. This is probably something most of you will point n00bs to…it’s intended to help bring those n00bs up a notch in their troubleshooting skillz, which ultimately will help you too.

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Designing your external DNS solution

2010-01-30

  One of my favourite subjects is DNS. I really love resolvers and queries, discussing the relative merits of recursion versus iteration, the different types of records that are out there, and how to tune DNS just so. Primaries and secondaries, AXFR or IXFR, tuning the TTL of your individual records so that you can [...]

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howto://Use SPF records to combat domain spoofing

2010-01-16

  Spam. When you’re talking about the Hormel product, love it. When you’re talking about unsolicited commercial email, I hate it with an abiding passion usually reserved only for the ankle-biter at Fox that cancelled Serenity. But any way you slice it, the bane of email’s existence is spam. Spam spam spam spam, lovely spam! [...]

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DNS self service on the cheap

2008-12-09

So last night, I got onto a bridge call at 2200, expecting to be off the call five minutes later. Not! I was supposed to put in a DNS change for a public facing site to accommodate a server migration. First they had cabling problems, then IIS was not happy, then the load balancer wasn’t [...]

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Disabling DHCP Authorisation checking in Windows

2008-08-20

While it shouldn’t be necessary, sometimes you find that you need to get around Windows’ process of checking with AD to see if it is authorised to service DHCP requests. This works in 2000, 2003, and should work in 2008 but has not been tested. To disable this check, create this registry key KEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\DHCPServer\Parameters \DisableRogueDetectionand [...]

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Creating DNS records at the command line

2008-08-12

Given a number of records that need to be added to DNS, we can create a file with the necessary information, and then run a cmd to read the data in the file and create the necessary records in DNS. The following assumes that all records are to be created in the same zone. Create [...]

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Creating DHCP reservations at the command line

2008-07-02

So we are in the process of migrating an entire network from one ip.addr range to another, and need to create a large number (>100) of reservations across various scopes at each location. While the GUI DHCP Admin tool is adequate to the task, I didn’t want to have to do that one at a [...]

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Change to DNS Root Servers

2007-11-05

On 2007-11-02, ISC announced a change to the ip.addr of the L.ROOT-SERVERS.NET server. In updating my root hints, I decided to check the other servers, and sure enough, the B.ROOT-SERVERS.NET server changed at some point in the past. While I am not sure when that happened, and being only one of thirteen it may not [...]

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ip protocol numbers

2007-09-07

This is just a summary of the more common assignments. See RFC 1700 for the complete list. Decimal Hex Keyword Protocol 0 0 Reserved 1 1 ICMP Internet Control Message 6 6 TCP Transmission Control 8 8 EGP Exterior Gateway Protocol 9 9 IGP any private interior gateway 17 11 UDP User Datagram 46 2E [...]

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Eight Simple Rules for Name Resolution

2007-08-29

Use fully qualified domain names in all that you do. Leverage centralised name resolution that is close to (local) to the client…that means DNS. Make sure all resources are registered in DNS using A records for the true hostnames in their ‘home’ domain. Where necessary, use CNAMEs to alias resource names, especially into other zones. [...]

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