wierd network problem: "no route to host" on some addresses

Question

Level 1

0 points

wierd network problem: "no route to host" on some addresses

Within the last few days I've been experiencing a weird problem with my Al Book G4 15.

I can connect to some hosts on the internet, but not others. I can get to Google and a lot of other sites (including this one), but not some, like youtube and myspace. Ping says "no route to host". Traceroute doesn't get off the machine.

This happens with either wifi or ethernet. Windows and Linux boxen on the same network have no problems. I also tried taking the router out of the equation and connecting directly to the cable modem. This made no difference.

I did some Google research and found some forum entries where people complained of similar symptoms. They were advised to run Tiger Cache Cleaner and AppleJack. I ran both of these to no avail.

Any ideas short of a full OS reload?

Thanks.

PS: here's my traceroute and dig output:

[host]:~ [user]$ traceroute youtube.com
traceroute: Warning: youtube.com has multiple addresses; using 208.65.153.251
traceroute to youtube.com (208.65.153.251), 64 hops max, 40 byte packets
traceroute: sendto: No route to host
1 traceroute: wrote youtube.com 40 chars, ret=-1
*traceroute: sendto: No route to host
traceroute: wrote youtube.com 40 chars, ret=-1
^C
[host]:~ [user]$ dig youtube.com

; <<>> DiG 9.2.2 <<>> youtube.com
;; global options: printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 42964
;; flags: qr rd ra; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;youtube.com. IN A

;; ANSWER SECTION:
youtube.com. 137 IN A 208.65.153.253
youtube.com. 137 IN A 208.65.153.251

;; Query time: 24 msec
;; SERVER: 68.87.71.226#53(68.87.71.226)
;; WHEN: Tue Feb 20 02:35:44 2007
;; MSG SIZE rcvd: 61
<br>
Powerbook 15" Al Mac OS X (10.4.8)

Posted on Feb 19, 2007 11:37 PM

Reply

Answer 1

Feb 20, 2007 12:19 AM in response to pjayb

can you open a terminal session, and type "ifconfig" please ? Paste the result into a reply.

I suspect your subnet mask is slightly erronous. Or possible your DNS maybe set incorrectly.

Reply

Answer 2

pjayb Author

Level 1

0 points

Feb 20, 2007 2:20 PM in response to Samuel Colak

ipconfig:
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
inet6 ::1 prefixlen 128
inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1
inet 127.0.0.1 netmask 0xff000000
gif0: flags=8010<POINTOPOINT,MULTICAST> mtu 1280
stf0: flags=0 mtu 1280
en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
ether 00:0a:95:9a:0a:8e
media: autoselect (none) status: inactive
supported media: none autoselect 10baseT/UTP <half-duplex> 10baseT/UTP <full-duplex> 10baseT/UTP <full-duplex,hw-loopback> 100baseTX <half-duplex> 100baseTX <full-duplex> 100baseTX <full-duplex,hw-loopback> 1000baseT <full-duplex> 1000baseT <full-duplex,hw-loopback> 1000baseT <full-duplex,flow-control> 1000baseT <full-duplex,flow-control,hw-loopback>
en1: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
inet6 fe80::20a:95ff:fef2:455c%en1 prefixlen 64 scopeid 0x5
inet 192.168.1.101 netmask 0xffffff00 broadcast 192.168.1.255
ether 00:0a:95:f2:45:5c
media: autoselect status: active
supported media: autoselect
fw0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 4078
lladdr 00:0a:95:ff:fe:9a:0a:8e
media: autoselect <full-duplex> status: inactive
supported media: autoselect <full-duplex>

netstat -nr:
Routing tables

Internet:
Destination Gateway Flags Refs Use Netif Expire
default 192.168.1.1 UGSc 16 5 en1
127 127.0.0.1 UCS 0 0 lo0
127.0.0.1 127.0.0.1 UH 13 59603 lo0
169.254 link#5 UCS 0 0 en1
192.168.1 link#5 UCS 3 0 en1
192.168.1.1 0:13:10:0:b4:1e UHLW 15 38 en1 1177
192.168.1.100 0:f:9f:6e:d9:45 UHLW 1 134 en1 989
192.168.1.101 127.0.0.1 UHS 0 0 lo0
192.168.1.102 0:9:5b:b8:69:de UHLW 0 8 en1 993

Internet6:
Destination Gateway Flags Netif Expire
::1 ::1 UH lo0
fe80::%lo0/64 fe80::1%lo0 Uc lo0
fe80::1%lo0 link#1 UHL lo0
fe80::%en1/64 link#5 UC en1
fe80::20a:95ff:fef2:455c%en1 0:a:95:f2:45:5c UHL lo0
ff01::/32 ::1 U lo0
ff02::/32 ::1 UC lo0
ff02::/32 link#5 UC en1

Thanks.

Reply

Answer 3

Feb 20, 2007 4:35 PM in response to pjayb

At first I thought it must have been Comcast, and did some
muttering under my breath about static routing. But then I read
about it working with other boxes on your network. So the
problem must reside there on your al book.

In addition to the ifconfig, could you also post the output from
netstat -r?

-Phil

Reply

Answer 4

Feb 21, 2007 7:46 AM in response to philsmith_

I've had the same strange problem. Everything works fine after a restart. I notice it after visiting websites from school and then trying to visit the site again from home.

I have also notice there is an entry for the sites I can't visit when I run netstat -r. It seems to be pointing an address at school (a nameserver?) that is not on my home network. Is there a way to flush those entries on the routing table?

Does anyone know why some sites and not others seem to be added to the routing table?

I'd include a copy of my routing table, but everything is working fine now.

MacBook Pro Mac OS X (10.4.8)

Reply

Answer 5

pjayb Author

Level 1

0 points

Feb 22, 2007 4:22 AM in response to philsmith_

netstat -r:

Routing tables

Internet:
Destination Gateway Flags Refs Use Netif Expire
default 192.168.1.1 UGSc 72 8 en1
127 localhost UCS 0 0 lo0
localhost localhost UH 19 63501 lo0
169.254 link#5 UCS 0 0 en1
192.168.1 link#5 UCS 5 0 en1
192.168.1.1 0:13:10:0:b4:1e UHLW 71 8 en1 1171
192.168.1.100 0:f:9f:6e:d9:45 UHLW 2 61 en1 1175
192.168.1.101 localhost UHS 0 0 lo0
192.168.1.102 0:9:5b:b8:69:de UHLW 0 1 en1 1174
192.168.1.255 ff:ff:ff:ff:ff:ff UHLWb 0 4 en1

Internet6:
Destination Gateway Flags Netif Expire
localhost localhost UH lo0
localhost Uc lo0
localhost link#1 UHL lo0
link#5 UC en1
peter-beardsleys-p 0:a:95:f2:45:5c UHL lo0
ff01:: localhost U lo0
ff02::%lo0 localhost UC lo0
ff02::%en1 link#5 UC en1

Reply

Answer 6

pjayb Author

Level 1

0 points

Feb 22, 2007 4:24 AM in response to reticular

Wierd, rebooting has no effect for me.

Reply

Answer 7

Feb 22, 2007 5:25 PM in response to pjayb

reticular, I understand your problem. You have a route which is
no longer valid. Yes, it can be removed (route del what.it.was
or route flush) but it's really just a matter of waiting no more
than 3 minutes. The TTL is listed in the netstat output, you can
watch it go down while you're waiting.

The reason for cacheing the routing information temporarily is that
a lot of work and traffic go into establishing a route. If a machine
has nabbed the MAC address of something it's likely to interface
with again soon, it would be silly to look all that up again.

Peter (may I call you that?), you're problem is more perplexing.
Looking at your network configuration and kernel routing table,
everything looks fine. I'll look again later to see if I missed something.
But from what I see, any traffic to youtube would go through the
router. But other machines go through the router without problem.
Soooo....

If I read everything correctly, traffic routed from your Mac is handled
differently from traffic from your PC's. That means there must be
a difference in the routing table in your router. For example, there
might be a static route which sends the Mac traffic to a different
gateway, and that gateway somehow blocks youtube.

I know this sounds incredibly improbable, but when you eliminate
all possiblities, what's left, however improbable, has to be the
answer. The next place to consult has to be your router.

-Phil

Reply

Answer 8

pjayb Author

Level 1

0 points

Feb 23, 2007 4:24 AM in response to philsmith_

I thought of that, but like I said, I tried connecting to the cable modem directly and it still exhibited the same behavior.

Oh well, thanks all for your help. I think I'm just going to re-install the OS and see what that gets me.

Reply

Answer 9

Mar 20, 2007 11:22 PM in response to pjayb

Hello:

I am facing exactly the same problem as reported by pjayb. Everything he has mentioned applies to me including youtube.com being one of the sites. I can get to google but not to gmail. For instance I know that any IP beginning with 208 or 209 - I cant get to it. There could be more.

I faced this problem before and after the upgrade to 10.4.9

I have also tried forcing a route and still does not work.

all esle is the same. Problem is the same whether its wireless or ethernet. Other windows laptops using the same wireless connection connetcs without a hitch. I am in Chennai, India

Thanks

Mini Mac OS X (10.4.9)

Reply