deathstar> ifconfig eth0 downdeathstar> ifconfig -aeth0      Link encap:Ethernet  HWaddr 00:23:ae:24:f6:76            inet addr:192.168.1.30  Bcast:192.168.1.255  Mask:255.255.255.0          BROADCAST MULTICAST  MTU:1500  Metric:1          RX packets:0 errors:0 dropped:0 overruns:0 frame:0          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0          collisions:0 txqueuelen:1000           RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)          Interrupt:18 lo        Link encap:Local Loopback            inet addr:127.0.0.1  Mask:255.0.0.0          inet6 addr: ::1/128 Scope:Host          UP LOOPBACK RUNNING  MTU:16436  Metric:1          RX packets:70 errors:0 dropped:0 overruns:0 frame:0          TX packets:70 errors:0 dropped:0 overruns:0 carrier:0          collisions:0 txqueuelen:0           RX bytes:5688 (5.5 KiB)  TX bytes:5688 (5.5 KiB)wlan0     Link encap:Ethernet  HWaddr 00:22:5f:7c:e7:cc            inet addr:192.168.1.37  Bcast:192.168.1.255  Mask:255.255.255.0          inet6 addr: fe80::222:5fff:fe7c:e7cc/64 Scope:Link          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1          RX packets:2057 errors:0 dropped:0 overruns:0 frame:6775          TX packets:2457 errors:1 dropped:0 overruns:0 carrier:0          collisions:0 txqueuelen:1000           RX bytes:1139421 (1.0 MiB)  TX bytes:346358 (338.2 KiB)          Interrupt:17 Base address:0xc000deathstar> iptables -L -nChain INPUT (policy ACCEPT)target     prot opt source               destination         Chain FORWARD (policy ACCEPT)target     prot opt source               destination         Chain OUTPUT (policy ACCEPT)target     prot opt source               destination         deathstar> route -nKernel IP routing tableDestination     Gateway         Genmask         Flags Metric Ref    Use Iface0.0.0.0         192.168.1.1     0.0.0.0         UG    0      0        0 wlan0192.168.1.0     0.0.0.0         255.255.255.0   U     0      0        0 wlan0deathstar> arp -aD-Link.Home (192.168.1.1) at 1c:7e:e5:b4:e1:6b [ether] on wlan0deathstar> ping 192.168.1.30 -c 1PING 192.168.1.30 (192.168.1.30) 56(84) bytes of data.64 bytes from 192.168.1.30: icmp_req=1 ttl=64 time=0.048 ms--- 192.168.1.30 ping statistics ---1 packets transmitted, 1 received, 0% packet loss, time 0msrtt min/avg/max/mdev = 0.048/0.048/0.048/0.000 msEDIT - IP addr/ip route infodeathstar> ip addr1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN     link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00    inet 127.0.0.1/8 scope host lo    inet6 ::1/128 scope host        valid_lft forever preferred_lft forever2: eth0: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast state DOWN qlen 1000    link/ether 00:23:ae:24:f6:76 brd ff:ff:ff:ff:ff:ff    inet 192.168.1.30/24 brd 192.168.1.255 scope global eth015: wlan0: <BROADCAST,ALLMULTI,PROMISC,NOTRAILERS,UP,LOWER_UP> mtu 1500 qdisc mq state UP qlen 1000    link/ether 00:22:5f:7c:e7:cc brd ff:ff:ff:ff:ff:ff    inet 192.168.1.37/24 brd 192.168.1.255 scope global wlan0    inet6 fe80::222:5fff:fe7c:e7cc/64 scope link        valid_lft forever preferred_lft foreverdeathstar> ip route show table alldefault via 192.168.1.1 dev wlan0 192.168.1.0/24 dev wlan0  proto kernel  scope link  src 192.168.1.37 broadcast 127.0.0.0 dev lo  table local  proto kernel  scope link  src 127.0.0.1 local 127.0.0.0/8 dev lo  table local  proto kernel  scope host  src 127.0.0.1 local 127.0.0.1 dev lo  table local  proto kernel  scope host  src 127.0.0.1 broadcast 127.255.255.255 dev lo  table local  proto kernel  scope link  src 127.0.0.1 broadcast 192.168.1.0 dev wlan0  table local  proto kernel  scope link  src 192.168.1.37 local 192.168.1.30 dev eth0  table local  proto kernel  scope host  src 192.168.1.30 local 192.168.1.37 dev wlan0  table local  proto kernel  scope host  src 192.168.1.37 broadcast 192.168.1.255 dev wlan0  table local  proto kernel  scope link  src 192.168.1.37 fe80::/64 dev wlan0  proto kernel  metric 256 unreachable default dev lo  table unspec  proto kernel  metric 4294967295  error -101local ::1 via :: dev lo  table local  proto none  metric 0 local fe80::222:5fff:fe7c:e7cc via :: dev lo  table local  proto none  metric 0 ff00::/8 dev wlan0  table local  metric 256 unreachable default dev lo  table unspec  proto kernel  metric 4294967295  error -101
Wheezy:ifconfig etho down - can still ping?
linux;networking
As you can see from the additional information you provided (the ip route output), the system still has a routing rule for 192.168.1.30:local 192.168.1.30 dev eth0  table local  proto kernel  scope host  src 192.168.1.30 The route -n command does not show any of the local routes, it only shows the main routing table (equivalent of ip route show table main). The ifconfig and route commands are legacy utilities that aren't updated any more. As such they're missing a lot of functionality present in other tools like the IProute2 suite (which provides the ip utility).But basically this route means that any traffic to 192.168.1.30 will go directly to the local address.There is this relevant bit from the Documentation/networking/operstates.txt:IF_OPER_DOWN (2):  Interface is unable to transfer data on L1, f.e.  ethernet is not  plugged or interface is ADMIN down.Linux differentiates interface state from IP state. Marking the interface as down simply means that interface cannot communicate with external hosts (L1 above referring to OSI network model layer 1). The IP itself is still present on the system and can be used.