linuxexpert-practice-labs/labs/lfcs/2-6-static-routing/README.md

LFCS 2.6: Static routing

Persistent static routes with NetworkManager and netplan, longest-prefix matching, keeping a second interface from adding a default route, and a host that routes between two networks.

Before you start

The lab gives this VM a second network interface, le-net2, with address 10.98.0.1/24: a NetworkManager profile called le-net2 on the RHEL family, /etc/netplan/60-le-net2.yaml on Ubuntu. Its gateways 10.98.0.254 and 10.98.0.253 don't need to answer for tasks 1 to 4.

For task 5 there are two more machines: the peer at 10.99.0.2 (network 10.99.0.0/24, this VM is 10.99.0.1 there) and far at 10.97.0.2 (network 10.97.0.0/24, this VM is 10.97.0.1 there). Neither has a default route. Get a shell on them with sudo ip netns exec lepeer bash and sudo ip netns exec le-far bash. They read their network settings at boot from /etc/netns/lepeer/network and /etc/netns/le-far/network (ip -batch commands, without the leading ip).

Tasks

1. RHEL family: give this VM a persistent route to 10.20.0.0/16 through 10.98.0.254, on its second network.
2. Ubuntu: do the same with netplan.
3. Add a more specific route, 10.20.5.0/24, through a different gateway, 10.98.0.253, persistently. Predict which gateway 10.20.5.9 and 10.20.6.9 go through, and write them to /root/lab-answers/3, one per line, in that order.
4. RHEL family: make the le-net2 profile never install a default route, so that ip route shows one default route, through the main interface.
5. Make this VM route between the peer's network and far's network, and give the peer and far routes to each other's network through it, all persistent, so they can ping each other and tracepath shows this VM as the first hop. If firewalld is running, let it forward between the two networks.

Hints

• nmcli connection modify le-net2 +ipv4.routes "NETWORK GATEWAY", then nmcli connection up le-net2.
• routes: with to: and via: in netplan, then netplan apply.
• ip route get ADDRESS.
• ipv4.never-default.
• net.ipv4.ip_forward = 1 in a file in /etc/sysctl.d/. firewalld forwards between interfaces it has put in one zone with --add-forward, or between zones with a policy; ufw route allow. tracepath -n.