Re: Troubleshooting connection loss (novice question)

Bit Twister wrote:
On Mon, 29 Oct 2007 22:09:28 GMT, Allen Weiner wrote:
(I don't know what SWAG stands for).

Such a Wild A$$ Guess

About DHCP lease, I power off my DSL modem every day at the end of a session. The loss of connection tends to occur about two hours into the session. (Wondering about a misbehaving cron job.).After the failure occurs,

Still not happy not knowing how long the lease is in the modem.


The modem DHCP lease time is 24 hours, according to the modem configuration page. It is 1:0:0:0 (D:H:M:S:)

The DHCP lease time according to Fedora is also 24 hours. (/var/lib/dhclient/dhclient-eth0.leases -> dhcp-lease-time 86400)
I'm unable to access the modem. (Firefox: browse http://192.168.1.1)

You should be able to get to the modem web page even if it lost it's
connection to ISP. First time you have a connection, verify you can ping -c 1 192.168.1.1

==========================================================================================
Ping 192.168.1.1 while connection established


[root@localhost ~]# ping -c 1 192.168.1.1
PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.
64 bytes from 192.168.1.1: icmp_seq=1 ttl=64 time=0.522 ms

--- 192.168.1.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.522/0.522/0.522/0.000 ms
[root@localhost ~]#

===============================================================================================
Ping 192.168.1.1 following connection loss

[root@localhost ~]# ping 192.168.1.1
PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.
From 192.168.1.47 icmp_seq=2 Destination Host Unreachable
From 192.168.1.47 icmp_seq=3 Destination Host Unreachable
From 192.168.1.47 icmp_seq=4 Destination Host Unreachable
From 192.168.1.47 icmp_seq=6 Destination Host Unreachable
From 192.168.1.47 icmp_seq=7 Destination Host Unreachable
From 192.168.1.47 icmp_seq=8 Destination Host Unreachable






======== chkconfig --list ==========
Double check if /avahi/ needs to be disabled on boot
avahi-daemon 0:off 1:off 2:off 3:on 4:on 5:on 6:off

Stop those avahi deamons from booting. You do not need them.

======== grep -v '^#' /etc/resolv.conf ==========
; generated by /sbin/dhclient-script
search myhome.westell.com
nameserver 192.168.1.1
nameserver 192.168.1.1

I would delete the search line to speed up DNS lookups.
and change the second nameserver to a public one if me.

======== hostname ==========
localhost.localdomain

Well, some deamons like to have a Full Qualified Domain Name (FQDN).
You created one, but I would not have picked localhost as a node name.

If you have not registered a domain name you can make one up and add
..invalid to it. Example nodes from my /etc/hosts

192.168.1.132 wb.home.invalid wb
192.168.1.31 wb7_0.home.invalid wb7_0
192.168.1.11 fw.home.invalid fw
192.168.1.12 wb1.home.invalid wb1




======== cat /etc/sysconfig/network ==========
NETWORKING=yes
HOSTNAME=localhost.localdomain

Here is where you can set your FQDN node name. Example:
HOSTNAME=wb.home.invalid

or HOSTNAME=darkstar.nowhere.invalid


============== head -15 /etc/hosts ===============


Well that bites. and can cause problems.
That hosts file need fixing. At best is should be

127.0.0.1 localhost.localdomain localhost

Give your node a FQDN and it would look something like
127.0.0.1 darkstar.nowhere.invalid darkstar localhost


Thanks very much for these suggestions as to how to optimize my networking setup. Everything I have is default. I just plugged in the modem. I'm a novice at Linux, bash scripting, and networking. Before making any changes to my networking config, I want to understand the purpose of the change. At the moment, I don't understand the rationales and possible side-effects for these changes . But on my to-do list is a bunch of reading material on Linux networking, so I will investigate these suggestions.
Ok, If it were me, I would set eht0 up as static so you know it can
talk to the Cable modem regardless if the modem does not hand out a
lease to your system. No sense fighting more than one thing at a time.

For trouble shooting, once you know physical connection is working you
ping each item in the path to the internet.

The mii-tool -v eth0 shows you if link is ok and nic shook hands with
whatever it is connected to. Now you know the physical connection is good.
On my most recent connection loss I did run mii-tool and ethtool to confirm that there was a link detected.


After ping yahoo's ip works you test DNS by pinging by name. Each ping has to
work to do the next step. Example for your system

ping -c 1 localhost # checks ping is working

ping -c 1 $(hostname -s) # pings your node name
# proves dns uses hosts file

ping -c 1 lan_gateway_ip_here # use gateway ip found in route -n
# yea, can access modem

ping -c 1 ISP_gateway_ip_here # you have to look in modem to find it
# yea, can access ISP's network

ping -c 1 66.94.234.13 # yahoo is up
# ISP is open to internet.

ping -c 1 yahoo.com # if works, dns is working


You might get ip addies for somewhere besides yahoo just incase.
My uneducated hunch is that I should first understand why, at time of connection loss, I can ping 192.168.1.47 but cannot ping 192.168.1.1 before going any further with DNS etc.
.

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