Ubuntu
maas package

  1. Bug #1664748
  2. Comment #6

Comment 6 for bug 1664748

Revision history for this message
Mike Pontillo (mpontillo) wrote :

Normal behavior is that the DHCP client begins to renew the lease half way through the lease time. So, for MAAS's 10 minute lease, it should be after ~5 minutes. After ~85-90% of the time (the rebind time), the client will give up on the lease and try to get a new one, under the assumption that maybe a different DHCP server took over.

Taking a closer look at the leases file, we can estimate when each lease renewed (though that information is unstated), and whether or not it was an expected outcome:

[Wired]
Lease 1: Not from MAAS. [10.1.8.277]
Lease 2: Renews 23:33:53 (so granted ~23:28:53) [OK] [10.0.0.112]
Lease 3: Renews 23:38:02 (so granted ~23:33:02) [RENEWED-OK] [10.0.0.112]
Lease 4: Renews 23:41:55 (so granted ~23:36:55) [RENEWED-OK] [10.0.0.112]
Lease 5: Renews 23:46:17 (so granted ~23:41:17) [RENEWED-OK] [10.0.0.112]

[WLAN]
Lease 6: Renews 23:30:52 (so granted ~23:25:52) [OK] [10.0.0.46]
Lease 7: Renews 23:41:27 (so granted ~23:36:27) [REBOUND; granted after rebind time of 23:35:43] [10.0.0.46]

On the wired interface, everything looks great. Leases are being renewed as expected.

The only questionable data point is the last lease (on the WLAN interface); it appears that this lease extended beyond the REBIND timeout, which caused the client to give up on the current lease and try to get a new lease instead.

Since the wired interface is okay, I think it's safe to assume that there is greater packet loss on the wireless interface, leading to the normal DHCP client behavior of giving up on the lease if it hasn't heard back from the server.

So on one hand, everything is operating normally, and maybe you should look at upgrading your WiFi network to prevent packet loss. ;-) On the other hand, yes, if you were to increase the timeout, that might help somewhat with this situation.

Increasing the timeout is a tricky balance; make it too long, and customers with small or highly utilized dynamic ranges will not be able to deploy new machines. Make it too short, and clients on networks experiencing packet loss, and/or poorly-written DHCP clients will lose their leases.