Why can't Macs ping each other on local network?

Question

Level 1

132 points

Why can't Macs ping each other on local network?

I've got two MacBooks running Leopard 10.5.6, both on the same WiFi network and both with valid local IP addresses (192.168.1.nn type). Each can ping the router which is running the network (192.168.1.254) and both can look at the Internet, and each can ping itself, but neither can ping the other. AFAICS I'm not running in Stealth mode and the Firewalls are letting stuff through. One of the machines is running Little Snitch, but this allows all connections on the local network.

When I try to ping, I get

ping: sendto: No route to host
ping: sendto: Host is down
ping: sendto: Host is down
ping: sendto: Host is down
ping: sendto: Host is down

What is going on? I can't find anything in the Help files.

TIA

iMac G5, Mac Mini (Intel), MacBook (Intel,early 08), Mac OS X (10.5.6), iSights, FW disks, digital cameras, Airport Express

Posted on Jan 15, 2009 8:23 AM

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Answer 1

baexandre

Level 2

285 points

Jan 15, 2009 8:50 AM in response to Living Fossil

if you disable the firewall of the mac that you are trying to ping, you will ping successfully 🙂

Firewall disable requests of such connections

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Answer 2

Living Fossil Author

Level 1

132 points

Jan 15, 2009 9:32 AM in response to baexandre

Thanks, but this doesn't seem to work: the only way I know to disable my built-in Firewall is to check "allow all incoming connections" in the Firewall tab of my Security Systems Pref. I've done this, but I still can't be pinged from the other machine. I have another location with two desktop Macs and my MacBook in a WiFi setup where all the machines can see each other - not just ping but file exchange etc. I can't work out what is different in the setup I've described here. Is it Little Snitch?

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Answer 3

Jan 17, 2009 5:38 AM in response to Living Fossil

same problem, stumped....

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Answer 4

Tim Haigh

Level 7

24,198 points

Jan 17, 2009 6:39 AM in response to Living Fossil

In the advanced setting of the firewall if stealth mode is enabled this will block pings. Disable that and all should be fine.

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Answer 5

Living Fossil Author

Level 1

132 points

Jan 17, 2009 6:49 AM in response to Tim Haigh

Doesn't work here. As I have already allowed all incoming connections, 'Advanced' is dimmed: if I choose another security option just so as to look at 'Advanced', I find Stealth Mode isn't enabled.

I am about to start up a PC on the network and see if one of the MacBooks (the one without Little Snitch) can ping and be pinged...

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Answer 6

BobHarris

Level 9

53,123 points

Jan 17, 2009 7:36 AM in response to Living Fossil

Is it Little Snitch?

Disable *Little Snitch* and find out.

You said earlier both Macs were on the same WiFi network. I just want to verify we are on the same page.

You have just 1 WiFi base station in your home?

You have just 1 Router in your home, and that router is the WiFi base station?

Because if you have 2 or more WiFi base stations or 2 or more routers, they have to be setup carefully to have just 1 and not 2 or more subnets.

And if you have multiple subnets all using 192.168.1.* private non-routeable addressing, then that could explain why pings are not getting through.

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Answer 7

Living Fossil Author

Level 1

132 points

Jan 17, 2009 10:27 AM in response to BobHarris

Thanks for the reply.

I thought I HAD disabled Little Snitch - for example I set it to its widest possible setting and then quit, but maybe I only quit from the configuration program and not LS itself (I wasn't my idea to install LS and I know very little about it).

As to the other questions: yes, there is just one wifi network and one router in the location in question. The router's local address is 192.168.1.254 and it can be pinged from either Mac (even the one running Little Snitch).

I have now taken the MacBook that has never run Little Snitch and have joined it to another wifi network with one PC in it. This PC can ping the MacBook and vice versa. This points to LS as the problem - but I'm in the wrong location, so I have to postpone the rest of the investigation until I get back there. I still don't understand why ping didn't work in either direction - I would have thought that LS would only block incoming connections. Mysterious things, networks.

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