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As an admin, it bugs me horribly when I personally have network issues I can't explain/get decipher - maybe you guys can shed some light.

Running a MacBook Air with the newest incarnation of Mac OS X (Mavericks), I sometime run into issues with public WiFi Hotspots. Basically, I connect to certain WiFi Hotspot, but don't really get a connection - no IP traffic is going through. Here is what i gathered so far:

In the non-working case, my routing table looks like this:

Shu:~ blitz$ netstat -nr
Routing tables

Internet:
Destination        Gateway            Flags        Refs      Use   Netif Expire
169.254            link#4             UCS             0        0     en0
192.168.182        link#4             UC              0        0     en0
192.168.182        link#4             UCSI            2        0     en0
192.168.182.1      20:4e:7f:8b:36:81  UHLWIir         1      208     en0    992
192.168.182.240    127.0.0.1          UHS             0        0     lo0
192.168.182.255    ff:ff:ff:ff:ff:ff  UHLWbI          0        1     en0

Internet6:
Destination                             Gateway                         Flags         Netif Expire
::1                                     ::1                             UHL             lo0
fe80::%lo0/64                           fe80::1%lo0                     UcI             lo0
fe80::1%lo0                             link#1                          UHLI            lo0
fe80::%en0/64                           link#4                          UCI             en0
fe80::1%en0                             50:7e:5d:95:45:2                UHLWI           en0
fe80::1240:f3ff:fe81:df32%en0           10:40:f3:81:df:32               UHLI            lo0
fe80::26ab:81ff:feb9:1b0%en0            24:ab:81:b9:1:b0                UHLWI           en0
fe80::5a55:caff:fe53:96e6%en0           58:55:ca:53:96:e6               UHLWI           en0
fe80::5e96:9dff:fe70:108a%en0           5c:96:9d:70:10:8a               UHLWI           en0
ff01::%lo0/32                           ::1                             UmCI            lo0
ff01::%en0/32                           link#4                          UmCI            en0
ff02::%lo0/32                           ::1                             UmCI            lo0
ff02::%en0/32                           link#4                          UmCI            en0

A ping to the local router (192.168.182.1) lead to this output:

shu:~ blitz$ ping 192.168.182.1
PING 192.168.182.1 (192.168.182.1): 56 data bytes
64 bytes from 192.168.182.1: icmp_seq=0 ttl=64 time=3.026 ms
64 bytes from 192.168.182.1: icmp_seq=0 ttl=64 time=3.323 ms (DUP!)
64 bytes from 192.168.182.1: icmp_seq=1 ttl=64 time=3.147 ms
64 bytes from 192.168.182.1: icmp_seq=1 ttl=64 time=3.227 ms (DUP!)
64 bytes from 192.168.182.1: icmp_seq=2 ttl=64 time=3.085 ms
64 bytes from 192.168.182.1: icmp_seq=2 ttl=64 time=3.975 ms (DUP!)

And the corresponding tcpdump during the ping shows this:

Shu:~ blitz$ sudo tcpdump
tcpdump: data link type PKTAP
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on pktap, link-type PKTAP (Packet Tap), capture size 65535 bytes
12:59:19.180358 IP 192.168.182.240 > 192.168.182.1: ICMP echo request, id 30483, seq 223, length 64
12:59:19.183449 IP 192.168.182.1 > 192.168.182.240: ICMP echo reply, id 30483, seq 223, length 64
12:59:19.183530 IP 192.168.182.1 > 192.168.182.240: ICMP echo reply, id 30483, seq 223, length 64
12:59:20.181503 IP 192.168.182.240 > 192.168.182.1: ICMP echo request, id 30483, seq 224, length 64
12:59:20.184755 IP 192.168.182.1 > 192.168.182.240: ICMP echo reply, id 30483, seq 224, length 64
12:59:20.184758 IP 192.168.182.1 > 192.168.182.240: ICMP echo reply, id 30483, seq 224, length 64

Now, when the connection works (which it sometimes does or which it does with other WiFis) I see this routing table:

shu:~ blitz$ netstat -nr
Routing tables

Internet:
Destination        Gateway            Flags        Refs      Use   Netif Expire
default            192.168.1.1        UGSc           33        5     en0
169.254            link#4             UCS             0        0     en0
192.168.1          link#4             UCS             2        0     en0
192.168.1.1        84:7a:88:66:c5:79  UHLWIir        34       66     en0   1170
192.168.1.150      127.0.0.1          UHS             1       25     lo0
192.168.1.255      ff:ff:ff:ff:ff:ff  UHLWbI          0       16     en0

My guess it the duplicated 192.168.182 line in the first netstat - but first of all, how does it get there, second what does it really do and third how do I get rid of it (besides rebooting, which is just crude :))

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migrated from serverfault.com Feb 16 at 14:00

This question came from our site for professional system and network administrators.

    
It's not you, it's the hotspot. Two machines are replying to its IP address. This is going to cause all sorts of chaos. –  Michael Hampton Feb 16 at 14:02
    
Nope, can't be it - rebooting my machine, and it works again - with the same IP! That's the really foo'd part about it. –  LordT Feb 16 at 14:15

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