overview to build a virtualized network topology from the most base elements it’s as simple as starting a virtual machine with the necessary number of virtualized interfaces and interconnecting these virtual interfaces to other virtual machines or physical interfaces. while there are tools1 which will nicely automate the creation of topologies and handle the lifecycle of VMs. all of these are effectively placing a nice wrapper around the following process....

you can have multiple pythons enabled at the same time so that those applications which you run which make assumptions about python2 being available work. (i’m looking at you gsutil and gcloud) elmo(~)% pyenv global 3.7.1 2.7.15 elmo(~)% pyenv versions system * 2.7.15 (set by /Users/sulrich/.pyenv/version) 2.7.15/envs/foo 2.7.5 * 3.7.1 (set by /Users/sulrich/.pyenv/version) 3.7.2 foo elmo(~)% which python2 /Users/sulrich/.pyenv/shims/python2 elmo(~)% which python3 /Users/sulrich/.pyenv/shims/python3 elmo(~)% which python /Users/sulrich/.pyenv/shims/python elmo(~)% python --version Python 3....

because i have to google these sysctl settings every … time.. /etc/sysctl.conf # disable IPv6 on the wlan0 interface net.ipv6.conf.wlan0.disable_ipv6=1 # insufficient on its lonesome net.ipv6.conf.wlan0.autoconf=0 # don't forget this .. it’s important to disable autoconf because it will still pick up the RAs for learning the default and this may not deterministically let you do what you want. replace wlan0 with the interface you want to starve.

it looks like the fact that folks pass communities around like the common cold is a bulb that is starting to light. oft discussed over beers, but little research in this space. here’s a first run at this research. must read paper: BGP communities: even more worms in the routing can update (20190323) it looks like one of the authors has written a few blog posts on the topic as well for the RIPE folks....