Tag Archives: networking

uceprotect lists subnets that never sent mail

Posted on 26 March 2026 by stuff writer

uceprotect.net claims to provide a blacklist of IP addresses that send spam. SMTP server operators can query the blacklist, and know to refuse mail from these IP addresses. That’s the theory. But there’s a problem though: uceprotect blocks IP address … Continue reading →

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FRR says “Finite State Machine Error” for IPv6 BGP on Linux

Posted on 3 November 2025 by stuff writer

If you turn off link-local addresses for the interface (those horrible 169.254.50.231 type addresses, and also the IPv6 fe80::dead:beef:4:f00d/64 things), FRR goes sulky. In netplan, it looks like this: When FRR is sulky, it says it will advertise IPv6 subnets, … Continue reading →

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IPv4 port routing for scaleable no-CGNAT NAT

Posted on 13 October 2025 by stuff writer

The CGNAT problem is that a big box at the ISP has to track the state of all communications on the network. This is expensive. It is also unnecessary. It’s 2025-10-13, and here’s an answer. Executive summary for TL;DR: Port … Continue reading →

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Workaround for Neighbour Discovery failure, for static-configured IPv6 on Linux: Use IPv4 gateway mac for IPv6

Posted on 5 June 2024 by stuff writer

Here’s a shell script to figure out what the IP4 gateway MAC address is, and to set that as the IP6 gateway MAC: This was necessary for a machine where the gateway decided that responding to neighbour solicit requests was … Continue reading →

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Ignoring out-of-band network policy systems with iptables

Posted on 7 August 2019 by stuff writer

I’ve been working on parental controls using an out-of-band policy engine. It is easy to subvert, if you care to, since the controls it implements are very light, and it is not actually part of the conversation between you and … Continue reading →

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What are the IP addresses for NS records of co.za?

Posted on 9 March 2017 by stuff writer

In short? 99.8% of the time, they are these: ns1.coza.net.za. IN A 66.135.62.20 ns.coza.net.za. IN A 206.223.136.200 ns4.iafrica.com. IN A 196.7.142.131 ns0.is.co.za. IN A 196.4.160.17 ns0.neotel.co.za. IN A 41.160.0.4 coza1.dnsnode.net. IN A 194.146.106.74 And the remaining 0.2% of the time?  … Continue reading →

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Invasion of the evil androids

Posted on 17 November 2016 by stuff writer

Google says you are too stupid to rule your own life.  They say this by their Android phone operating system, in which they do not give you, the owner and operator of the device, root permissions.  This means: You cannot … Continue reading →

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The sound of outage

Posted on 26 March 2015 by stuff writer

Here’s a song to sing the next time your network goes down.  Click the play button on the youtube karaoke, and sing it yourself: Hello outage my old friend I’ve come to talk with you again Because of vulnerability creeping … Continue reading →

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VMWare + ipfix + NAT = intermittent fail

Posted on 21 May 2014 by stuff writer

So I put all of these things together a while ago for bandwidth reporting: VMWare‘s netflow reporting – I configured a virtual distributed switch to send netflow reporting to a collector.  Every time some machine runs up its internet usage, the … Continue reading →

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Netgear STP bug (or something)

Posted on 27 February 2014 by stuff writer

I found a fun bug today. We have a stack of netgear switches in our office – and we keep getting disconnected at odd times. I already found a switch which did not have STP enabled, and turned that on, … Continue reading →

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