I had a weird problem with dhclient. It looks like the problem is
with ifconfig.

I start with an IP address 213.53.69.44. Then I set the address
to 213.53.69.195. I see a gratuitous ARP, but some packets keep
being sent with the old IP address.

This is NetBSD 1.6_STABLE.

---------------------------------------------------------------------------
einstein# ifconfig rtk0 
rtk0: flags=8b43<UP,BROADCAST,RUNNING,PROMISC,ALLMULTI,SIMPLEX,MULTICAST> mtu 1500
        address: 00:20:ed:19:48:62
        media: Ethernet autoselect (100baseTX full-duplex)
        status: active
        inet 213.53.69.44 netmask 0xffffff00 broadcast 213.53.69.255
        inet6 fe80::220:edff:fe19:4862%rtk0 prefixlen 64 scopeid 0x1
        inet6 2001:6e0:206:1:220:edff:fe19:4862 prefixlen 64
einstein# ping 204.152.184.116
PING www.netbsd.org (204.152.184.116): 56 data bytes
64 bytes from 204.152.184.116: icmp_seq=0 ttl=242 time=158.178 ms
64 bytes from 204.152.184.116: icmp_seq=1 ttl=242 time=157.915 ms
64 bytes from 204.152.184.116: icmp_seq=2 ttl=242 time=157.504 ms
64 bytes from 204.152.184.116: icmp_seq=3 ttl=242 time=157.823 ms
^C
----www.netbsd.org PING Statistics----
4 packets transmitted, 4 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 157.504/157.855/158.178/0.278 ms
einstein#
---------------------------------------------------------------------------

13:14:27.599738 213.53.69.44 > 204.152.184.116: icmp: echo request
13:14:27.757153 204.152.184.116 > 213.53.69.44: icmp: echo reply
13:14:28.614347 213.53.69.44 > 204.152.184.116: icmp: echo request
13:14:28.772171 204.152.184.116 > 213.53.69.44: icmp: echo reply
13:14:29.604277 213.53.69.44 > 204.152.184.116: icmp: echo request
13:14:29.761691 204.152.184.116 > 213.53.69.44: icmp: echo reply
13:14:30.604208 213.53.69.44 > 204.152.184.116: icmp: echo request
13:14:30.761942 204.152.184.116 > 213.53.69.44: icmp: echo reply

---------------------------------------------------------------------------

einstein# ifconfig rtk0 213.53.69.195 netmask 255.255.255.0

---------------------------------------------------------------------------

13:14:45.953960 arp who-has 213.53.69.195 tell 213.53.69.195
13:14:54.530053 arp who-has 213.53.69.39 tell 213.53.69.195
13:14:54.530180 arp reply 213.53.69.39 is-at 0:50:da:3d:2:f6
13:14:54.530200 213.53.69.195.65514 > 213.53.69.39.53:  15713+ PTR? 116.184.152.204.in-addr.arpa. (46)
13:14:54.530754 213.53.69.39.53 > 213.53.69.195.65514:  15713 1/2/0 (125)
13:14:54.531584 arp who-has 213.53.69.14 tell 213.53.69.195
13:14:54.532214 arp reply 213.53.69.14 is-at 0:c0:5:0:1c:d6

---------------------------------------------------------------------------

einstein# ifconfig rtk0 
rtk0: flags=8b43<UP,BROADCAST,RUNNING,PROMISC,ALLMULTI,SIMPLEX,MULTICAST> mtu 1500
        address: 00:20:ed:19:48:62
        media: Ethernet autoselect (100baseTX full-duplex)
        status: active
        inet 213.53.69.195 netmask 0xffffff00 broadcast 213.53.69.255
        inet6 fe80::220:edff:fe19:4862%rtk0 prefixlen 64 scopeid 0x1
        inet6 2001:6e0:206:1:220:edff:fe19:4862 prefixlen 64
einstein# ping 204.152.184.116
PING www.netbsd.org (204.152.184.116): 56 data bytes
^C
----www.netbsd.org PING Statistics----
3 packets transmitted, 0 packets received, 100.0% packet loss
einstein#

---------------------------------------------------------------------------

13:14:54.532234 213.53.69.44 > 204.152.184.116: icmp: echo request
13:14:54.689954 204.152.184.116 > 213.53.69.44: icmp: echo reply
13:14:55.532515 213.53.69.44 > 204.152.184.116: icmp: echo request
13:14:55.689855 204.152.184.116 > 213.53.69.44: icmp: echo reply
13:14:56.542480 213.53.69.44 > 204.152.184.116: icmp: echo request
13:14:56.699978 204.152.184.116 > 213.53.69.44: icmp: echo reply

---------------------------------------------------------------------------

Any strange caching bug?

	rvdp