Tag Archives: IPv6

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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