Mac OS X machine can’t reach other servers on the LAN

Question

My Mac can’t reach other servers on the LAN.

janos@macbook:~$ netstat -r
Routing tables
Internet:
Destination        Gateway            Flags        Refs      Use   Netif Expire
default            192.168.0.1        UGSc           19        0     en1
127                localhost          UCS             0        0     lo0
localhost          localhost          UH              6     6515     lo0
169.254            link#5             UCS             0        0     en1
192.168.0          link#5             UCS             2        0     en1
192.168.0.1        cc:35:40:2a:ed:2d  UHLWIir        20        0     en1    204
192.168.0.11/32    link#5             UCS             0        0     en1
m                  link#5             UHRLWI          0      904     en1      8

What is the link#5 routing table and how can I delete it? I already tried:

sudo route -n flush

But it didn’t helped. m is a server on the LAN. I put it into my hosts file on the Mac.

janos@macbook:~$ ping m
PING m (192.168.0.13): 56 data bytes
Request timeout for icmp_seq 0
ping: sendto: No route to host
Request timeout for icmp_seq 1
ping: sendto: Host is down
Request timeout for icmp_seq 2
ping: sendto: Host is down
Request timeout for icmp_seq 3
^C
--- m ping statistics ---
5 packets transmitted, 0 packets received, 100.0% packet loss
janos@macbook:~$ ssh m
ssh: connect to host m port 22: Host is down

If it’s possible I would like a clean routing table like this:

janos@lenovo:~$ route
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
default         192.168.0.1     0.0.0.0         UG    0      0        0 wlan0
192.168.0.0     *               255.255.255.0   U     9      0        0 wlan0

Solution 1

I know this question is old, but I just had a similar problem where I couldn't ping or connect in any way from my MacBook to any devices on network despite internet working fine on all devices meaning they are all connected to the same wifi router and all devices had been restarted.

The solution was: restart the wifi router!

Solution 2

If I understand well what you said, your Mac (IP 192.168.0.11) can’t ping another server on the same subnet (192.168.0.13).

In this case, the route is unused as the destination IP is in the same subnet. You may have an ARP cache issue. You could try to flush the ARP entry for 192.168.0.13 with sudo arp -d 192.168.0.13 command and try again to ping 192.168.0.13.

Comments

[EEAA]

Have you talked with your network team about this?

[Admin]

There's no network team only a LAN, a Ubuntu server and 2 clients (a macbook, a lenovo laptop). The lenovo can ping or connect to the m server. I used to use a proxy on the macbook but I don't use it anymore and it was not connected while I was doing the tests above.

[EEAA]

1) link#X refers to a specific network device in your machine. 2) What is the IP address of m?

[Janos]

How can I find out what is the link#5? How can I remove it? 2) The ip of the server is: 192.168.0.13

[Janos]

It says 192.168.0.13 (192.168.0.13) deleted and then the ping is Request timeout for icmp_seq...

[Arnaud Léonard]

You probably have a network problem on your mac. Do you use a DHCP on your network or are the IP address statically configured ? Is your mac able to ping the lenovo PC ?

[Janos]

I'm using DHCP on my network. No, the mac can not ping the lenovo PC. And this line 192.168.0 link#5 UCS 3 0 en1 is still in the routing table. Anybody knows how to remove it?

[Arnaud Léonard]

I have the same line on my Mac, with no problem to ping other machines on the same subnet. I don't think this line poses a problem. I suppose you already tried to reboot the mac ?

[Janos]

Yes, I did tried to reboot it. It didn't helped. Do you also have 7 lines in your routing table?

[Arnaud Léonard]

The number of lines depends on the number of network interface. All I can tell you is that I have all the lines you have, except the last one m link#5. As I undertand it, the R flag means that this route is unreachable. I'm sorry I can't tell you why. Maybe you could try sudo route delete m

[Janos]

I did the sudo route delete m. It removed the line from the routing table, but the ping ...13 from the macbook was still not working. I also tried sudo route add -host 192.168.0.13 192.168.0.11 and sudo route add -host 192.168.0.13 192.168.0.1 with no luck.

[Janos]

I don't think there is a problem with the network card. I was using wifi and the macbook to write this question. The internet connection is working except the LAN. I turned off the wifi and changed to Ethernet to write this comment. Pinging the router (192.168.0.1) works, macbook (192.168.0.11) works, lenovo (192.168.0.12) works, ubuntu server (192.168.0.13) 100% packet loss.

[Arnaud Léonard]

Ok, so the situation evolved since yesterday. You said, 18 hours ago, that the mac wasn't able to ping the lenovo PC and now, it can. The problem could come from the server then : firewall rule, incorrect arp cache. Do you have root access on the ubuntu server ?

[Janos]

I was pinging 192.168.0.18 which doesn't exists, removed the m line with route delete m, pinging 192.168.0.13 (NOT m!), restarted the macbook a few times and finally I was able to ssh m. I don't have a clue why, but it works now. If you know why please write it in a comment. I would appreciate it. My routing table is the following now: pastebin.com/5X4mm0fz I'm still curious what happens if the Expire reaches zero.

[Janos]

And restart the mac.

[Vaibhav Jain]

can't believe I wasted 6 hours for this.

[Jammer]

OMG ... I'm glad I found this within 30 mins! @VaibhavJain I FEEL YOUR PAIN! :)

[nick carraway]

How to force the mac to use the gateway anyway?