Comment 5 for bug 61989

I marked earlier bug #58927 about the same issue as duplicate of this as this had one duplicate already and the description/title is more concise. Anyway, I'll repeat some info the other bug:

The bug is actually in the crappy router which reports too low value for interface-mtu (64 in all reports I have seen). Why this worked fine in dapper is because dhclient did not ask for interface-mtu then and the default value is used instead in that case, and the network works fine. Then dhclient.conf was changed to include "interface-mtu" query in Debian and the package was imported to Ubuntu post-dapper. Most of the routers cannot be fixed to return correct interface-mtu, so the dhcp should not ask for it by default. This very same "bug" was actually fixed once already (from the changelog):

dhcp3 (3.0.1-1ubuntu4) hoary; urgency=low
  * Revert changes to debian/dhclient.conf, apparently at least some DHCP servers supply broken interface-mtu information, so this isn't safe to enable without broader testing (Ubuntu #8241)

I hope it will fixed again before edgy :)