LinuxQuestions.org
LinuxAnswers - the LQ Linux tutorial section.
Go Back   LinuxQuestions.org > Forums > Linux Forums > Linux - Networking
User Name
Password
Linux - Networking This forum is for any issue related to networks or networking.
Routing, network cards, OSI, etc. Anything is fair game.

Notices

Reply
 
Search this Thread
Old 12-08-2003, 08:41 PM   #1
monkeyman2000
Member
 
Registered: Oct 2003
Posts: 68

Rep: Reputation: 15
no longer get network access beyond router


Hi,

I have a small home network with 2 machines (desktop and laptop, both with RedHat 9) and a dlink router/hub/access point. Both machines access the internet throught ethernet connections to the router. Both had been working fine with no problems.

Then I put a pcmcia modem on the laptop so I could use it to access the internet on the road. I disconnected the laptop from the ethernet and set up KPPP to use the modem to acces the internet. Once I got this set up, I took out the modem and reattached the laptop to the ethernet network.

Now, however, the laptop will not access the internet or anything beyond the router. The laptop can ping the router, and it can ping the desktop,but when I try to ping a machine on the internet beyond the router, I get:

$ ping yahoo.com
PING yahoo.com (66.218.71.198) 56(84) bytes of data.

--yahoo.com ping statistics---
20 packets transmitted, 0 received, 100% packet loss

(so it successfully resolves the IP address of the remote machine but cannot ping [or receive pings] from it)

I can still ping machines on the internet from the desktop machine.

So I presume what happened was that setting up kppp changed some configuration files that had been working so now they don't. I haven't been able to figure out what, though.

Both machines have similar /sbin/route outputs:

desktop$ /sbin/route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.0.0 * 255.255.255.0 U 0 0 0 eth0
139.254.0.0 * 255.255.0.0 U 0 0 0 eth0
127.0.0.0 * 255.0.0.0 U 0 0 0 lo
default router 0.0.0.0 UG 0 0 0 eth0
desktop$


laptop$ /sbin/route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.0.0 * 255.255.255.0 U 0 0 0 eth0
139.254.0.0 * 255.255.0.0 U 0 0 0 eth0
127.0.0.0 * 255.0.0.0 U 0 0 0 lo
default router 0.0.0.0 UG 0 0 0 eth0
laptop$

...and idential resolv.conf files:

$ cat /etc/resolv.conf
; generated by /sbin/dhclient-script
search localhost.localdomain
nameserver 192.168.0.1
$

Does anybody know what went wrong and how to fix it? Thanks for any help you can give!!
 
Old 12-08-2003, 09:05 PM   #2
ToniT
Senior Member
 
Registered: Oct 2003
Location: Zurich, Switzerland
Distribution: Debian/unstable
Posts: 1,357

Rep: Reputation: 47
Can you ping the desktop machine from laptop or vice versa? What your 'ifconfig' or 'ifconfig -a' looks like?
 
Old 12-08-2003, 09:14 PM   #3
monkeyman2000
Member
 
Registered: Oct 2003
Posts: 68

Original Poster
Rep: Reputation: 15
Yes, the laptop & desktop can ping each other (and login to each other). The desktop can also ping & otherwise access machines beyond the router, but the laptop cannot.

ifconfig output:

laptop$ /sbin/ifconfig
eth0 Link encap:Ethernet HWaddr 00:E1:19:0A:16:F5
inet addr:192.168.0.101 Bcast:192.168.0.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:225 errors:0 dropped:0 overruns:0 frame:0
TX packets:73 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:18550 (18.1 Kb) TX bytes:8781 (8.5 Kb)
Interrupt:11 Base address:0xc000

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:10 errors:0 dropped:0 overruns:0 frame:0
TX packets:10 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:700 (700.0 b) TX bytes:700 (700.0 b)
laptop$

desktop $ /sbin/ifconfig
eth0 Link encap:Ethernet HWaddr 00:38:34:8A:63:F9
inet addr:192.168.0.102 Bcast:192.168.0.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:32427 errors:0 dropped:0 overruns:0 frame:0
TX packets:30547 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:18373521 (17.5 Mb) TX bytes:4370030 (4.1 Mb)
Interrupt:9 Base address:0xa000

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:19 errors:0 dropped:0 overruns:0 frame:0
TX packets:19 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:2032 (1.9 Kb) TX bytes:2032 (1.9 Kb)

desktop $

Last edited by monkeyman2000; 12-08-2003 at 09:21 PM.
 
Old 12-09-2003, 03:21 PM   #4
ToniT
Senior Member
 
Registered: Oct 2003
Location: Zurich, Switzerland
Distribution: Debian/unstable
Posts: 1,357

Rep: Reputation: 47
hmm.. configurations seem correct and very similar (in a positive way).

Few things to check comes into mind.

What does the 'ping router' say in different computers (if the ip address is wrong, it can probably be found from /etc/hosts file)?

Are there any firewall configurations that could block transfers in the router or in the laptop ('iptables -v -L' or 'ipchains -v -L' should show if there is any strange)?
 
Old 12-09-2003, 03:54 PM   #5
monkeyman2000
Member
 
Registered: Oct 2003
Posts: 68

Original Poster
Rep: Reputation: 15
Thanks for helping me, ToniT.

Quote:
Originally posted by ToniT

What does the 'ping router' say in different computers (if the ip address is wrong, it can probably be found from /etc/hosts file)?
laptop # ping router
PING router (192.168.0.1) 56(84) bytes of data.
64 bytes from router (192.168.0.1): icmp_seq=1 ttl=63 time=0.546 ms
64 bytes from router (192.168.0.1): icmp_seq=2 ttl=63 time=0.456 ms
64 bytes from router (192.168.0.1): icmp_seq=3 ttl=63 time=0.477 ms
64 bytes from router (192.168.0.1): icmp_seq=4 ttl=63 time=0.491 ms

--- router ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3004ms
rtt min/avg/max/mdev = 0.456/1.411/4.221/1.622 ms
laptop #


desktop # ping router
PING router (192.168.0.1) 56(84) bytes of data.
64 bytes from router (192.168.0.1): icmp_seq=1 ttl=63 time=0.493 ms
64 bytes from router (192.168.0.1): icmp_seq=2 ttl=63 time=0.536 ms
64 bytes from router (192.168.0.1): icmp_seq=3 ttl=63 time=0.519 ms
64 bytes from router (192.168.0.1): icmp_seq=4 ttl=63 time=0.465 ms

--- router ping statistics ---
4 packets transmitted, 4 received, 0% packet loss, time 3033ms
rtt min/avg/max/mdev = 0.465/0.503/0.536/0.031 ms
desktop #




Quote:
Are there any firewall configurations that could block transfers in the router or in the laptop ('iptables -v -L' or 'ipchains -v -L' should show if there is any strange)? [/B]
I don't believe so, but I am not so familiar with firewalls... iptables output is below.

laptop # iptables -v -L
Chain INPUT (policy ACCEPT 2669 packets, 157K bytes)
pkts bytes target prot opt in out source destination
2716 164K RH-Lokkit-0-50-INPUT all -- any any anywhere anywhere

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination
0 0 RH-Lokkit-0-50-INPUT all -- any any anywhere anywhere

Chain OUTPUT (policy ACCEPT 6774 packets, 1618K bytes)
pkts bytes target prot opt in out source destination

Chain RH-Lokkit-0-50-INPUT (2 references)
pkts bytes target prot opt in out source destination
35 5648 ACCEPT udp -- any any router anywhere udp spt:domain dpts:1025:65535
2 120 ACCEPT tcp -- any any anywhere anywhere tcp dpt:ssh flags:SYN,RST,ACK/SYN
10 700 ACCEPT all -- lo any anywhere anywhere
0 0 REJECT tcp -- any any anywhere anywhere tcp dpts:0:1023 flags:SYN,RST,ACK/SYN reject-with icmp-port-unreachable
0 0 REJECT tcp -- any any anywhere anywhere tcp dpt:nfs flags:SYN,RST,ACK/SYN reject-with icmp-port-unreachable
0 0 REJECT udp -- any any anywhere anywhere udp dpts:0:1023 reject-with icmp-port-unreachable
0 0 REJECT udp -- any any anywhere anywhere udp dpt:nfs reject-with icmp-port-unreachable
0 0 REJECT tcp -- any any anywhere anywhere tcp dpts:x11:6009 flags:SYN,RST,ACK/SYN reject-with icmp-port-unreachable
0 0 REJECT tcp -- any any anywhere anywhere tcp dpt:xfs flags:SYN,RST,ACK/SYN reject-with icmp-port-unreachable
laptop #

Output on the desktop machine, for comparison:

desktop # /sbin/iptables -v -L
Chain INPUT (policy ACCEPT 18781 packets, 9384K bytes)
pkts bytes target prot opt in out source destination
18923 9412K RH-Lokkit-0-50-INPUT all -- any any anywhere anywhere

Chain FORWARD (policy ACCEPT 0 packets, 0 bytes)
pkts bytes target prot opt in out source destination

Chain OUTPUT (policy ACCEPT 18718 packets, 12M bytes)
pkts bytes target prot opt in out source destination

Chain RH-Lokkit-0-50-INPUT (1 references)
pkts bytes target prot opt in out source destination
103 23614 ACCEPT udp -- any any router anywhere udp spt:domain dpts:1025:65535
0 0 ACCEPT tcp -- any any anywhere anywhere tcp dpt:6346 flags:SYN,RST,ACK/SYN
1 60 ACCEPT tcp -- any any anywhere anywhere tcp dpt:ssh flags:SYN,RST,ACK/SYN
0 0 ACCEPT udp -- eth0 any anywhere anywhere udp spts:bootps:bootpc dpts:bootps:bootpc
0 0 ACCEPT udp -- eth1 any anywhere anywhere udp spts:bootps:bootpc dpts:bootps:bootpc
38 4677 ACCEPT all -- lo any anywhere anywhere
0 0 REJECT tcp -- any any anywhere anywhere tcp dpts:0:1023 flags:SYN,RST,ACK/SYN reject-with icmp-port-unreachable
0 0 REJECT tcp -- any any anywhere anywhere tcp dpt:nfs flags:SYN,RST,ACK/SYN reject-with icmp-port-unreachable
0 0 REJECT udp -- any any anywhere anywhere udp dpts:0:1023 reject-with icmp-port-unreachable
0 0 REJECT udp -- any any anywhere anywhere udp dpt:nfs reject-with icmp-port-unreachable
0 0 REJECT tcp -- any any anywhere anywhere tcp dpts:x11:6009 flags:SYN,RST,ACK/SYN reject-with icmp-port-unreachable
0 0 REJECT tcp -- any any anywhere anywhere tcp dpt:xfs flags:SYN,RST,ACK/SYN reject-with icmp-port-unreachable
desktop #
 
Old 12-09-2003, 05:23 PM   #6
ToniT
Senior Member
 
Registered: Oct 2003
Location: Zurich, Switzerland
Distribution: Debian/unstable
Posts: 1,357

Rep: Reputation: 47
There indeed are some firewall settings. Thus, if i looked correctly, they shoud just drop some well known portscans. Anyways, 'iptables --t nat --flush; iptables -t mangle --flush ; iptables --flush' should drop these settings (one error source less).

These are getting shots in the dark, but what does a command 'ip route' say (ip is an other command to configure net routing by using new kernel interface; comes with a package called iproute2). If the ip command is missing, then everything is fine (most that can only be seen by the ip command, can only be messed by it [like traffic shaping and such]).
 
Old 12-09-2003, 06:25 PM   #7
monkeyman2000
Member
 
Registered: Oct 2003
Posts: 68

Original Poster
Rep: Reputation: 15
Quote:
Originally posted by ToniT
[B]There indeed are some firewall settings. Thus, if i looked correctly, they shoud just drop some well known portscans. Anyways, 'iptables --t nat --flush; iptables -t mangle --flush ; iptables --flush' should drop these settings (one error source less).
OK, flushed the IP tables... but it doesn't make any difference, still can't get beyond the router (with the laptop).


Quote:
These are getting shots in the dark, but what does a command 'ip route' say
The output of ip route is identical on both machines:

# ip route
192.168.0.0/24 dev eth0 scope link
139.254.0.0/16 dev eth0 scope link
127.0.0.0/8 dev lo scope link
default via 192.168.0.1 dev eth0
#
 
Old 12-09-2003, 06:40 PM   #8
balam
Member
 
Registered: Nov 2002
Location: us
Distribution: red hat
Posts: 143

Rep: Reputation: 15
what is your dns settngs

onthe linux box, what is your dns settings,
they should be the ones that Isp uses, if youhave a linksys routes just login in to it. and go to shtatus, and there will be listed dns server ips, copy them and open you nic card config and add them. save it, and make sure that network demons restart.
 
Old 12-09-2003, 07:01 PM   #9
monkeyman2000
Member
 
Registered: Oct 2003
Posts: 68

Original Poster
Rep: Reputation: 15
Re: what is your dns settngs

Hi balam thanks for helping me.

I don't think DNS is the problem. Let me explain. Both my boxes are RedHat 9 linux, both connect to the Dlink gateway, which connects to the internet via DSL.

The desktop box accesses the internet fine. It can ping internet machines by name or by IP address. The laptop cannot ping internet machines by either name or IP address.

Both machines have the following /etc/resolv.conf:

#cat /etc/resolv.conf
; generated by /sbin/dhclient-script
search localhost.localdomain
nameserver 192.168.0.1
#

192.168.0.1 is the Dlink gateway. It seems to provide correct DNS information and internet access to the desktop, but no longer to the laptop.

The laptop has no problems accessing the local network so its network interface is obviously working as far as that goes.
 
Old 12-09-2003, 08:19 PM   #10
balam
Member
 
Registered: Nov 2002
Location: us
Distribution: red hat
Posts: 143

Rep: Reputation: 15
did you try the laptop on dchp
 
Old 12-10-2003, 01:20 AM   #11
monkeyman2000
Member
 
Registered: Oct 2003
Posts: 68

Original Poster
Rep: Reputation: 15
Quote:
Originally posted by balam
did you try the laptop on dchp
Just tried this, and it led me to the solution... or rather to a workaround to a very odd problem.

The problem appears to be with my access point, a Dlink DI-714. I have it's DHCP server set to reserve IP addresses for my 2 machines -- 192.168.0.102 for the desktop & 192.168.0.101 for the laptop. This has always worked with no problems.

Now, however, the 192.168.0.101 address seems not to work for some reason. I changed this address to several others (.99, .110, etc).. they all worked fine. When I tried to set it back to .101, no dice. Very odd. I have checked all the obvious things... there is no other .101 on the network, the hostname is right, I restarted the access point several times, and so on. There is very little documentation on the DLink DI-714 and it's hard to diagnose the problem. I would like to understand what caused it (if anyone has any idea let me know). For now I have just changed to a new IP address.

Thanks very much to ToniT and balam for your ideas... they really helped me.
 
Old 12-10-2003, 09:57 AM   #12
balam
Member
 
Registered: Nov 2002
Location: us
Distribution: red hat
Posts: 143

Rep: Reputation: 15
I am not shure but I have the feeling that is about your ip scheme. .0.x
 
Old 12-10-2003, 01:04 PM   #13
monkeyman2000
Member
 
Registered: Oct 2003
Posts: 68

Original Poster
Rep: Reputation: 15
Quote:
Originally posted by balam
I am not shure but I have the feeling that is about your ip scheme. .0.x
But I have been using the same IP addresses for years without a problem.

And now everything works again as long as I don't use 192.168.0.101 for the laptop. Currently I am using 192.168.0.108... I tested it with several others, all worked except 192.168.0.101.

When I tested using different IP addresses I changed the reserved address on the Dlink, then changed the fixed IP address on the laptop (using redhat-config-network which modifies the ./sysconfig/networking/ files (ifcfg-eth0). I restarted the network daemons (/etc/init.d/network restart) and checked the ip address wiith ifconfig to confirm it had changed... all worked except .101 (!!!!)
 
Old 12-11-2003, 07:47 PM   #14
zaphodiv
Member
 
Registered: Oct 2003
Distribution: Slackware
Posts: 388

Rep: Reputation: 30
>default router 0.0.0.0 UG 0 0 0 eth0
That is the problem. The default gateway should be the ip address of the dlink router.
 
  


Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
ndiswrapper no longer working on mandrake after change of router djzanni Linux - Wireless Networking 2 08-22-2005 02:45 PM
Can no longer connect to wireless access point ebaker Linux - Wireless Networking 2 03-23-2005 09:23 PM
Network card pings ok, but can't access web via router BeerMonster Linux - Networking 7 11-09-2003 10:46 AM
Installed router, dial-up Internet no longer works. (MDK 9.1) mcarter Linux - Networking 1 09-01-2003 03:18 PM
apache problems..no longer able to access domains marvc Linux - Software 7 06-07-2003 05:24 AM


All times are GMT -5. The time now is 05:38 AM.

Main Menu
My LQ
Write for LQ
LinuxQuestions.org is looking for people interested in writing Editorials, Articles, Reviews, and more. If you'd like to contribute content, let us know.
Main Menu
Syndicate
RSS1  Latest Threads
RSS1  LQ News
Twitter: @linuxquestions
identi.ca: @linuxquestions
Facebook: linuxquestions Google+: linuxquestions
Open Source Consulting | Domain Registration