Team two NICs on lin-srv and prove the team survives losing one

short · 45 min · Objective 2.2

Task

Give lin-srv a second network adapter, bond the two into an active-backup team with a static address, and prove the point of teaming: disconnect one adapter while a continuous ping runs, and count how many replies are lost. Then record the subnet arithmetic for the lab network so the addressing is documented rather than remembered.

Steps

  1. Create a bond in active-backup mode with both adapters as members, link monitoring on (miimon=100, or mii-monitor-interval: 100 in netplan -- without it the bond never notices a pulled cable), and the static address 192.168.56.10/24. Save ip -br addr to lab/teaming/addr.txt and cat /proc/net/bonding/bond0 to lab/teaming/bond.txt.
  2. From win-srv or the host, run a continuous ping to 192.168.56.10.
  3. In the hypervisor, disconnect the active adapter's virtual cable. Wait 20 seconds, then reconnect it. Stop the ping and save its summary to lab/teaming/ping.txt.
  4. Save cat /proc/net/bonding/bond0 again to lab/teaming/bond-after.txt and note which adapter is now active.
  5. Write lab/teaming/subnet.txt with the lines network:, mask:, broadcast:, first_host:, last_host: and hosts: for 192.168.56.0/24, and the same for a /27 that starts at 192.168.56.64.

Verify

These checks run in a POSIX shell: Terminal on macOS or Linux, and on Windows Git Bash (it comes with Git for Windows) or WSL. A stock Windows PowerShell or Command Prompt has no awk or grep, so there the first line fails.

grep -c 'bond0' lab/teaming/addr.txt
grep -Eic 'active-backup|fault-tolerance' lab/teaming/bond.txt
grep -Eo '[0-9]+% (packet )?loss' lab/teaming/ping.txt
grep -c 'Slave Interface' lab/teaming/bond-after.txt
grep -Ec 'hosts: (254|30)$' lab/teaming/subnet.txt
grep -Ec 'broadcast: 192.168.56.(255|95)$' lab/teaming/subnet.txt

The bond carries the address, is in active-backup mode and still lists two members. The ping loss should be a few per cent at most -- a handful of replies during the switchover -- rather than everything while the cable was out. The /24 has 254 hosts ending at broadcast .255; the /27 at .64 has 30 hosts and broadcast .95.

Notes

Active-backup works with any switch. Aggregation modes such as LACP need the switch ports configured to match, which is why they are not used in this lab: the hypervisor's virtual switch does not negotiate LACP.

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