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< section >
< h2 > Learning about slightly more advanced networking with linux< / h2 >
< p > < b > Paul Warren< / b > < / p >
< p > Mastodon: @pwarren@mastodon.thewarrens.name < / p >
< p > email: paul at thewarrens.name < / p >
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< p > © 2021 Paul Warren< / p >
< p > CC BY-NC-SA< p >
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< / section >
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< section > < h2 style = "color:red" > ! WARNING !< / h2 >
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< p > I am not a network engineer, there are gaps in my knowledge< / p >
< p > The words I use might not be the correct ones< / p >
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< p > Please don't blame me if your network stops networking< / p >
< p class = "fragment" > Maybe don't go and try building an ISP based off this talk :)< / p >
< / section >
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< section > < h2 > What even is a network?< / h2 >
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< p class = "fragment fade-in-then-out" > Ethernet?< / p >
< p class = "fragment fade-in-then-out" > Token Ring?< / p >
< p class = "fragment fade-in-then-out" > IPX?< / p >
< p class = "fragment fade-in-then-out" > AX.25?< / p >
< / section >
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< section > < h2 > What even is a network?< / h2 >
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< p class = "fragment fade-in-then-out" > ipv4?< / p >
< p class = "fragment fade-in-then-out" > ipv6?< / p >
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< p class = "fragment fade-in-then-out" > tcp?< / p >
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< p class = "fragment" > Allows connections between computers< / p >
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< aside class = "notes" >
< p > We are going to mostly focus on Ethernet and IPv6< / p >
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< / section >
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< section > < h2 > Managed networks< / h2 >
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< p class = "fragment" > < b > Controls< / b > connections between computers< / p >
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< p class = "fragment" > < b > Scales< / b > connections between computers< / p >
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< p class = "fragment" > < img src = "3tier.png" / > < p >
< aside class = "notes" >
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< p > Most of us probably work in a managed network< / p >
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< p > Most of us probably have a pretty flat edge network at home< / p >
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< p > Diagram is nice, but hides complexities at each layer.< p >
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< / aside >
< / section >
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< section > < h2 > Layers!< / h2 >
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< p class = "fragment" > Like an onion!< / p >
< p class = "fragment" > That 7 layer thing from the OSI< / p >
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< p class = "fragment" > Ethernet -> IP -> ICMP/TCP/UDP< / p >
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< p class = "fragment" > Administrative overlays< / p >
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< p class = "fragment" > VPNs and Tunnels< / p >
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< aside class = "notes" >
< p > or a parfait< / p >
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< p > which you can mostly ignore, as what we generally use doesn't conform to it. But it does provide a good framework for assisting understanding< / p >
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< p > Like firewalls, web-proxies/SSL MITM, But also access rights etc< / p >
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< / aside >
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< / section >
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< section > < h2 > Layers< / h2 >
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< p > This means the Physical layers do not have to match the Logical connections< / p >
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< p class = "fragment" > Networks are also a bit fractal in nature< / p >
< p class = "fragment" > For the purposes of this talk, we can ignore a lot of complexity< / p >
< / section >
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< section > < h2 > An easy one!< / h2 >
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< p > VLANS< / p >
< p class = "fragment" > Ethernet layer< / p >
< p class = "fragment" > Designed to limit broadcast storms< / p >
< p class = "fragment" > Can also separate IP networks on the same Ethernet< / p >
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< p class = "fragment" > Tagged and Untagged/Default< / p >
< p class = "fragment" > IEEE 802.1Q< / p >
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< aside class = "notes" >
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< p > beware of strange implementations, windows seems to take Router Advertisements from all vlans, regardless of tag< / p >
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< / aside >
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< / section >
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< section > < h2 > VLANs in linux< / h2 >
< p > Are pretty easy!< / p >
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< pre class = "fragment" > < code data-trim data-noescape >
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ip link add link enp0s2 name enp0s2.2501 vlan id 2501
ip -6 addr add 2001:db8:2501::10/64 dev enp0s2.2501
ip link set dev enp0s2.2501 up
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< / code >
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< / pre >
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< / section >
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< section > < h2 > VLANs in linux< / h2 >
< p > Various different methods of making it go in different distributions< / p >
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< p class = "fragment" > Debian: in /etc/network/interfaces< / p >
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< pre class = "fragment" >
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< code > auto enp1s0.2502
iface enp1s0.2502 inet dhcp
iface enp1s0.2502 inet6 auto< / code >
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< / pre >
< p class = "fragment" > OpenWRT has a nice GUI< / p >
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< aside class = "notes" >
< p > OpenWRT: can also use the hardware present on most hardware routers to assign vlans to specific ports< / p >
< / section >
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< section > < h2 > What even is a router?< / h2 >
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< p class = "fragment" > Two or more interfaces< / p >
< p class = "fragment" > Some logic to determine where a packet goes< / p >
< aside class = "notes" >
< p > Not necessarily physical< / p >
< p > Sounds simple right?< / p >
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< / aside >
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< / section >
< section > < h2 > Linux Routing< / h2 >
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< p > Add to sysctl config:< / p >
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< pre class = "fragment" > < code data-trim data-noescape >
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net.ipv4.ip_forward = 1
net.ipv6.conf.all.forwarding = 1
net.ipv6.conf.default.forwarding = 1
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< / code >
< / pre >
< p class = "fragment" > And we're done!< / p >
< p class = "fragment" > Yeah, not really :)< / p >
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< / section >
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< section > < h2 > Static Routes< / h2 >
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< p > Manually added, or scripted routes that don't change< / p >
< pre > < code data-trim data-noescape >
ip route add 172.17.0.0/24 via 172.16.0.254 dev wg0
< / code >
< / pre >
< / section >
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< section > < h2 > Static Routes< / h2 >
< pre width = "110%" > < code width = "110%" > ip -6 route add 2001:db8:2501::/64 via 2001:db8:2500::1 dev enp0s1
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ip -6 route add 2001:db8:2502::/64 via 2001:db8:2500::1 dev enp0s1
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ip -6 route add 2001:db8:2600:beef:/64 via 2001:db8:face::1 dev wg0< / code >
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< / pre >
< aside class = "notes" >
< p > As you can imagine this quickly becomes unwieldy with expanding networks< / p >
< / aside >
< / section >
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< section > < h2 > Static Routes< / h2 >
< img src = "Diagrams/MyVLansExt.png" > < / img >
< / section >
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< section > < h2 > Enter dynamic routes< / h2 >
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< p class = "fragment" > Advertise your LANs< / p >
< p class = "fragment" > Discovering routes to other LANs< / p >
< p class = "fragment" > Optional: Do some logic< / p >
< p class = "fragment" > Add them to the routing table< / p >
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< p class = "fragment" > Userspace daemons< / p >
< p class = "fragment" > talking to the kernel networking stack< / p >
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< / section >
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< section > < h2 > Dynamic Routing< / h2 >
< p > Open Shortest Path First (OSPF)< / p >
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< p > Uses Dijkstra's algorithm< / p >
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< p class = "fragment" > RFC2328< / p >
< p class = "fragment" > RFC5340< / p >
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< p class = "fragment" > For: Dynamic routes inside your networks< / p >
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< / section >
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< section > < h2 > Dynamic Routing< / h2 >
< p > Border Gateway Protocol (BGP)< / p >
< p class = "fragment" > RF4271< / p >
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< p class = "fragment" > For: Sharing dynamic routes outside your network with other Autonomous Sytstems (AS)< / p >
< notes class = "aside" >
< p > "AS" is used a lot in the ISP world, and your ISP will have an assigned AS Number< / p >
< / notes >
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< / section >
< section > < h2 > The Userspace Daemons< / h2 >
< p > BIRD: Berkeley Internet Routing Daemon< / p >
< p > Quagga: Fork of Zebra< / p >
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< p > OpenBGPd/OpenOSPFd: from the OpenBSD project< / p >
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< p class = "fragment" > Significant overlap, but they are different< / p >
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< p class = "fragment" > I've not used Quagga, or the OpenBSD ones< / p >
< p class = "fragment" > There are probably others!< / p >
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< / section >
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< section > < h2 > intro to bird< / h2 >
< p > Powerful< / p >
< p class = "fragment" > Complex to configure< / p >
< p class = "fragment" > Use version control< / p >
< aside class = "notes" >
< p > Not quite turing complete< / p >
< p > git on /etc/bird or wherever your distor stores it.< / p >
< / aside >
< / section >
< section > < h2 > Intro to bird configuration< / h2 >
< p > /etc/bird.conf< / p >
< p > Each router needs a unique ID< / p >
< p >
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< aside class = "notes" >
< p > Set BIRD's router ID. It's a world-wide unique identification of your router, usually one of router's IPv4 addresses. Default: the lowest IPv4 address of a non-loopback interface. < p >
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< / section >
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< section > < h2 > Intro to bird configuration< / h2 >
< p > KNorries diagram here< / p >
< / section >
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< section > more detail on bird< / section >
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< section > A Simple Network< / section >
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< section > Multi Host IPs (Authoritative DNS example like in the facebook thing)< / section >
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< section > Why use a 'real' router< / section >
< section > < h2 > ¿Por qué no los dos?< / h2 >
< p > OpenWRT is a linux based distribution for real networking hardware< / p >
< aside class = "note" >
< p > Consumer grade mostly, but some enterprise level routers are supported< / p >
< / section >
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< section > < h2 > Bonus homework< / h2 >
< p > Why did I use 2001::db8::/32?< / p >
< p > Why did I use /64s?< / p >
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< p > I highly recommend going through KNorrie's network examples: < a href = "https://github.com/knorrie/network-examples" > https://github.com/knorrie/network-examples< / a > < / p >
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< p > OSPF Areas< / p >
< p > Automatic transfers of internal aggregates to BGP (Something I've not investigated much)< / p >
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< / section >
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< section > < h2 > Resources< / h2 >
< p > These slides: < a href = "https://gitea.pwarren.id.au/pwarren/SysAdmin2022" > https://gitea.pwarren.id.au/pwarren/SysAdmin2022< / a > < / p >
< p > bird: < a href = "https://bird.network.cz/" > https://bird.network.cz< / a > < / p >
< p > Openwrt: < a href = "https://openwrt.org" > https://openwrt.org/< / a > < / p >
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< p > The OpenWRT IRC channel, currently on the OFTC network< / p >
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< p > BenEater's < a href = "https://www.youtube.com/watch?v=-wMU8vmfaYo" > "Why was facebook down for five hours" < / a > < / p >
< p > 802.1Q: < a href = "https://www.ieee802.org/1/pages/802.1Q-2014.html" / > < / p >
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< / section >
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< section > < h2 > Unused Bits< / h2 > < / section >
< section > < h2 > What I'm assuming we're familiar with< / h2 >
< p > Diagram showing standard leaf node of a network with a bit cloud containg "The rest of the org"< / p >
< / section >
< section > < h2 > What we're familiar with< / h2 >
< p > Diagram showing added storage and server network< p >
< / section >
< section > < h2 > How things evolve< / h2 >
< p > Uh Oh, we've got a new Datacentre< / p >
< / section >
< section > < h2 > How things evolve< / h2 >
< p > which has its own lot of storage and servers< / p >
< / section >
< section > < h2 > How things evolve< / h2 >
< p > And now people want to work in Tasmania!< / p >
< / section >
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