DHCP within pupin

DHCP within pupin appears to have difficulties. more than once, i've connected a client using DHCP to the network in pupin, been granted a DHCP lease, and then been rejected in my attempts to renew the lease. here's a snippet from /var/log/syslog showing this transaction:

Feb  2 11:30:47 localhost ifplugd(wired)[4288]: client: Sending on   Socket/fallback
Feb  2 11:30:49 localhost kernel: wired: no IPv6 routers present
Feb  2 11:30:51 localhost dhclient: DHCPDISCOVER on wired to 255.255.255.255 port 67 interval 7
Feb  2 11:30:51 localhost ifplugd(wired)[4288]: client: DHCPDISCOVER on wired to 255.255.255.255 port 67 interval 7
Feb  2 11:30:51 localhost dhclient: DHCPOFFER from 128.59.168.1
Feb  2 11:30:51 localhost dhclient: DHCPREQUEST on wired to 255.255.255.255 port 67
Feb  2 11:30:51 localhost ifplugd(wired)[4288]: client: DHCPOFFER from 128.59.168.1
Feb  2 11:30:51 localhost ifplugd(wired)[4288]: client: DHCPREQUEST on wired to 255.255.255.255 port 67
Feb  2 11:30:51 localhost dhclient: DHCPACK from 128.59.168.1
Feb  2 11:30:51 localhost ifplugd(wired)[4288]: client: DHCPACK from 128.59.168.1
Feb  2 11:30:52 localhost dhclient: bound to 128.59.171.209 -- renewal in 1751 seconds.
Feb  2 11:30:52 localhost ifplugd(wired)[4288]: client: bound to 128.59.171.209 -- renewal in 1751 seconds.
Feb  2 11:30:52 localhost ifplugd(wired)[4288]: Program executed successfully.
Feb  2 11:31:01 localhost kernel: usb 2-1: new low speed USB device using uhci_hcd and address 2
Feb  2 11:50:55 localhost -- MARK --
Feb  2 11:54:34 localhost kernel: usb 2-1: USB disconnect, address 2
Feb  2 11:58:54 localhost kernel: usb 2-1: new low speed USB device using uhci_hcd and address 3
Feb  2 12:00:03 localhost dhclient: DHCPREQUEST on wired to 128.59.62.25 port 67
Feb  2 12:00:34 localhost last message repeated 3 times
Feb  2 12:01:40 localhost last message repeated 7 times
Feb  2 12:02:44 localhost last message repeated 4 times
Feb  2 12:03:53 localhost last message repeated 4 times
Feb  2 12:04:53 localhost last message repeated 4 times
Feb  2 12:05:53 localhost last message repeated 4 times
Feb  2 12:06:43 localhost last message repeated 4 times
Feb  2 12:07:55 localhost last message repeated 4 times
Feb  2 12:08:55 localhost last message repeated 4 times
Feb  2 12:09:05 localhost dhclient: DHCPREQUEST on wired to 128.59.62.25 port 67
Feb  2 12:09:46 localhost last message repeated 4 times
Feb  2 12:10:46 localhost last message repeated 4 times
Feb  2 12:11:38 localhost last message repeated 4 times
Feb  2 12:12:42 localhost last message repeated 4 times
Feb  2 12:13:50 localhost last message repeated 5 times
Feb  2 12:14:40 localhost last message repeated 4 times
Feb  2 12:15:45 localhost last message repeated 4 times
Feb  2 12:16:48 localhost last message repeated 4 times
Feb  2 12:16:59 localhost dhclient: DHCPREQUEST on wired to 128.59.62.25 port 67
Feb  2 12:17:01 localhost /USR/SBIN/CRON[1954]: (root) CMD (   run-parts --report /etc/cron.hourly)
Feb  2 12:17:17 localhost dhclient: DHCPREQUEST on wired to 128.59.62.25 port 67
Feb  2 12:17:48 localhost last message repeated 2 times
Feb  2 12:18:53 localhost last message repeated 6 times
Feb  2 12:19:55 localhost last message repeated 5 times
Feb  2 12:20:50 localhost last message repeated 4 times
Feb  2 12:21:48 localhost last message repeated 4 times
Feb  2 12:22:49 localhost last message repeated 5 times
Feb  2 12:23:05 localhost dhclient: DHCPREQUEST on wired to 128.59.62.25 port 67
Feb  2 12:23:22 localhost dhclient: DHCPREQUEST on wired to 255.255.255.255 port 67
Feb  2 12:23:22 localhost dhclient: DHCPNAK from 128.59.168.1
Feb  2 12:23:22 localhost dhclient: DHCPDISCOVER on wired to 255.255.255.255 port 67 interval 7
Feb  2 12:23:22 localhost dhclient: DHCPOFFER from 128.59.168.1
Feb  2 12:23:22 localhost dhclient: DHCPREQUEST on wired to 255.255.255.255 port 67
Feb  2 12:23:22 localhost dhclient: DHCPACK from 128.59.168.1
Feb  2 12:23:22 localhost dhclient: bound to 128.59.171.66 -- renewal in 1741 seconds.

Interestingly, after the first failure of the renewal, renewing the new lease works fine, at least for now, and i get gradually increasing lease durations:

Feb  2 12:50:55 localhost -- MARK --
Feb  2 12:52:23 localhost dhclient: DHCPREQUEST on wired to 128.59.62.25 port 67
Feb  2 12:52:23 localhost dhclient: DHCPACK from 128.59.62.25
Feb  2 12:52:23 localhost dhclient: bound to 128.59.171.66 -- renewal in 2378 seconds.
Feb  2 13:04:57 localhost kernel: usb 2-1: USB disconnect, address 3
Feb  2 13:17:01 localhost /USR/SBIN/CRON[5756]: (root) CMD (   run-parts --report /etc/cron.hourly)
Feb  2 13:30:55 localhost -- MARK --
Feb  2 13:32:01 localhost dhclient: DHCPREQUEST on wired to 128.59.62.25 port 67
Feb  2 13:32:01 localhost dhclient: DHCPACK from 128.59.62.25
Feb  2 13:32:01 localhost dhclient: bound to 128.59.171.66 -- renewal in 19249 seconds.