No route to host for two web sites - and only on this MacBook?

Question

No route to host for two web sites - and only on this MacBook?

Interesting one this.

Most of my day's spent using Windows machines, so I'm more familiar with why they sometimes can't connect to sites (or have DNS issues, etc). However, this MacBook Pro recently decided that it wouldn't be able to route to two sites: mediamonkey.com and barebones.com. This happens in Firefox and Safari, and also happens regardless of which wireless network I use (we have two separate ADSL connections in the office).

A Vista machine can ping, traceroute to and load both sites fine. This problem has persisted on the MBP for several weeks now, and I've tried all I can - static IPs, assigning different DNS servers etc - but nothing seems to make it work.

Is there something I'm missing? It can resolve everything else fine. Heck, it can even resolve the two sites I'm having problems with so I'm confident DNS isn't the problem - it just can't route to them. Any ideas anybody?

MacBook Pro1,1, Mac OS X (10.5.8), Safari 4.0.3, FF 3.5

Posted on Oct 7, 2009 3:36 AM

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Answer 1

Oct 7, 2009 12:58 PM in response to Chris W (Work)

You have probably tried this but I may as well ask.
Does a traceroute to the affected sites fail on the MBP? If not, does using the affected sites IP address work in Safari or Firefox instead of the URL?
The traceroute on the MBP should follow the same path as the Vista machine.

Also is the MTU size the same in the MBP as the Vista machine?

regards

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Answer 2

Oct 8, 2009 2:45 AM in response to rack0 tack0

The traces fail (no route to host).

Trying the IPs results in the same problem in Safari, Firefox or Opera. :/

ifconfig | grep "mtu" = en1: 1500 (as I'd expect). The Vista machine also runs with an MTU of 1500. At a bit of a loss now really, I'm about to go try 1492 but I can't imagine it'd make a difference just going to the router...

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Answer 3

Oct 8, 2009 6:40 AM in response to Chris W (Work)

Try flushing the DNS cache on your MacBook:

dscacheutil -flushcache

See if that helps...

charlie

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Answer 4

Oct 8, 2009 7:38 AM in response to Chris W (Work)

Try Charlies suggestion but it does not seem to be DNS.

Where does the traceroute fail on its first hop to your router or out on the internet.
You have 2 ADSL connections, is the DHCP client on the MAC picking up the correct routing.
Do you have IPv6 turned off? It can cause problems if its not required.
Does the netstat -r command give any clues?

I use 1492 for the MTU, more from historic reasons than anything else.

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Answer 5

Oct 8, 2009 8:17 AM in response to rack0 tack0

We have two ADSL connections but they're physically discrete networks (different IP ranges, different wireless networks, the lot). More for reasons of infrastructure than anything else (one for VoIP and uploading with its faster upstream, the other for bulk traffic).

The trace doesn't even get to hop 1, it just fails with a no route to host. IPv6 is not turned off, never thought it might cause a problem. Might it be because those two sites are advertising IPv6 addresses (and this is being picked up in DNS but there's no IPv6 routing in place on our connections?)

Actually, scratch that last paragraph. Even with IPv6 disabled and connecting to the second WLAN, I still can't trace or resolve either site.

A puzzle wrapped in an enigma...

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Answer 6

Oct 8, 2009 8:37 AM in response to Chris W (Work)

any info int the netstat -r printout? But why only two websites.

Worked with computers for nearly 30 years, they still amaze me, there is a logical reason for this but I am not sure what!

regards

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Answer 7

Oct 8, 2009 9:53 AM in response to rack0 tack0

I know, driving me barmy too! (I've been tinkering with them for about 18 years now so you've won that one 😉

With IPv6 disabled, netstat -r presents with the following symptoms:

macbookpro:~ christopher$ netstat -r
Routing tables

Internet:
Destination Gateway Flags Refs Use Netif Expire
default router1 UGSc 39 0 en1
10.2.2/24 link#6 UCS 3 0 en1
router1 0:1d:7e:ed:90:1e UHLW 51 1404 en1 1197
Mac-mini.revhq 0:14:51:2d:87:7e UHLW 0 297 en1 592
macbookpro.revhq localhost UHS 1 2110 lo0
10.2.2.255 link#6 UHLWb 2 137 en1
127 localhost UCS 0 0 lo0
localhost localhost UH 3 158 lo0
169.254 link#6 UCS 0 0 en1

Internet6:
Destination Gateway Flags Netif Expire
localhost link#1 UHL lo0
fe80::%lo0 localhost Uc lo0
localhost link#1 UHL lo0
ff01:: localhost U lo0
ff02:: localhost UC lo0

Can't see anything immediately obvious...

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Answer 8

Oct 8, 2009 11:29 AM in response to Chris W (Work)

Ok,
Three more points and then you will need to go through the routers logs and the Macbook Pros logs.
Perhaps I should have started with these.
If you use this machine on another network (home) does it behave the same way?
Is there a firewall on the machine such as Little Snitch that could be causing it, if not try trashing the Apple fire wall plist and resetting it. Or move it to the desktop instead of trashing it to be safe.
If you use the Ethernet does it still fail?

Then its down to the logs.

Not being much help here.
regards

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Answer 9

Oct 9, 2009 4:10 AM in response to rack0 tack0

rack0 tack0 wrote:
Ok,
Three more points and then you will need to go through the routers logs and the Macbook Pros logs.
Perhaps I should have started with these.
If you use this machine on another network (home) does it behave the same way?
Is there a firewall on the machine such as Little Snitch that could be causing it, if not try trashing the Apple fire wall plist and resetting it. Or move it to the desktop instead of trashing it to be safe.
If you use the Ethernet does it still fail?

Then its down to the logs.

Not being much help here.
regards

I'll part-answer now:

No firewall on the machine. Not tried this machine at home but suspect it would behave similarly (our ADSL connections are from two separate ISPs, and the hardware used on both is totally different as well). Where's the .plist for the firewall kept? (too lazy to Google at this second 😉

Cheers
C

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Answer 10

Oct 9, 2009 7:46 AM in response to Chris W (Work)

A bit a a problem, my system is 10.6 not 10.5 so it may be different but on this machine its:-
HD/Library/Preferences/com.apple.alf.plist .

Two other thing that seems to clear problems is the old repair permissions and safe boot, there simple and easy to to, have you tried them?
Repair permissions is in disk utility and safe boot is performed by holding the shift key down while it boots up (until you see the spinning circle on the grey screen). It takes a while to boot up into safe mode.
regards

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Answer 11

Oct 12, 2009 9:17 AM in response to Chris W (Work)

Are you using Peer Guardian? I was having the same issue that you're describing and found out that it's an issue with PeerGuardian's filters.

Check out this link: http://ki6esh.com/2009/08/05/mac-os-x-problems-solutions-no-route-to-host/

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Answer 12

Oct 12, 2009 10:16 AM in response to Donnie Shilling

Donnie Shilling wrote:
Are you using Peer Guardian? I was having the same issue that you're describing and found out that it's an issue with PeerGuardian's filters.

Check out this link: http://ki6esh.com/2009/08/05/mac-os-x-problems-solutions-no-route-to-host/

Unbelievable! I had a look in Apps, and (lo and behold) PeerGuardian was there, active, and blocking the two sites:

PG2 logs:
Mon Oct 12 2009 18:01:43.457 BST -Blck- local:0 -> 209.200.50.117:80 (http) tcp4 'Safari (4928)' (Webair Internet Development Inc:Ads, Spyware, Bogon, etc)
Mon Oct 12 2009 18:02:09.640 BST -Blck- local:0 -> 199.232.79.70:80 (http) tcp4 'Safari (4928)' (Cambridge Entrepreneurial Network split2:Ads, Spyware, Bogon, etc)

Why two pefectly valid, legit sites are being blocked as malware sources is beyond me... But it's not the first time I've been stumped by their classification of IP ranges.

I'm incredibly frustrated (but laughing at the same time) because I didn't even put PG2 on this MBP! (most likely the person who used the laptop before me, he used to take it home ocasionally so why am I not surprised?)

The irony is I've actually fallen foul of PG2's arbitrary blockings before on my own machine - I noticed on my desktop a while back that PG2's list makers decided to include the BBC for a while. However as the Windows client stays in the systray I noticed it flashing when I couldn't load a site, and quickly worked around it. Ironic that PG2 on OSX doesn't have a Launcher icon to flash at me 😉

Thank you for pointing out this (blindingly obvious) cause - I uninstalled PG2 and those two sites worked first time. My thanks to all who gave me advice or offered suggestions to try and fix it; I learnt the command for flushing a Mac's DNS cache so I've learnt at least one new thing today.

Marking as solved! Hurray. Thanks Apple user community 🙂

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