not getting a default gateway through dhcp

Ever since I moved to this ISP I've been having network problems, and I
need a little help.

They gave me an antique motorolla cable modem, and usually I have a
linksys router plugged into the router, but right now I have my FC4 pc
plugged in directly into the modem, to rule out any problems with the
router.

For the last couple of days the connection was ok, but this afternoon it
rained, and, since my ISP's service depends on the weather, the network
went down. If it rains, it goes down, if it's windy, it goes down, if
there's lightening, you guessed it, it goes down. It's an ISP from hell.

Now I've configured eth0 with dhcp. It does get an IP address, but when I
try to connect anywhere, it says no route to something (I can't check
exactly what it says right now, because I'm trying to send this).

I see network activity in gkrellm and I see ARP packets with ethereal,
so the link is ok. So I look at the routing table, and I see no default
gateway. But I did see some DHCP packets coming in, so I figured that must
be the gateway. I do

route add default gateway xx.xx.xx.xx

and then voila! I'm online.

Now that I got this far, I want to pinpoint where the problem is.
Why am I not getting the default gateway? Is it some bug in my FC4 dhcp
client, or is my stupid ISP that's not sending it. Is it possible to tell?

As a matter of fact, I installed the dhcp server on this machine, and my
other machines as well as the router got all the required info just fine.
I do want to go out through the router though, and I want it to get all
the info, as it should. I am positive my hardware is ok, except possibly
the motorolla cable modem, which is from the ISP.

Below is the DHCP packet I saw with ethereal. Please someone help, before
I end up in a mad house.


No. Time Source Destination Protocol Info
4693 186.355671 24.35.40.1 255.255.255.255 DHCP DHCP Offer - Transaction ID 0x33d1a0

Frame 4693 (363 bytes on wire, 363 bytes captured)
Arrival Time: Jul 5, 2005 19:52:47.244828000
Time delta from previous packet: 0.120903000 seconds
Time since reference or first frame: 186.355671000 seconds
Frame Number: 4693
Packet Length: 363 bytes
Capture Length: 363 bytes
Protocols in frame: eth:ip:udp:bootp
Ethernet II, Src: 00:50:57:00:99:a6, Dst: ff:ff:ff:ff:ff:ff
Destination: ff:ff:ff:ff:ff:ff (Broadcast)
Source: 00:50:57:00:99:a6 (Broadban_00:99:a6)
Type: IP (0x0800)
Internet Protocol, Src Addr: 24.35.40.1 (24.35.40.1), Dst Addr: 255.255.255.255
(255.255.255.255)
Version: 4
Header length: 20 bytes
Differentiated Services Field: 0x07 (DSCP 0x01: Unknown DSCP; ECN: 0x03)
0000 01.. = Differentiated Services Codepoint: Unknown (0x01)
.... ..1. = ECN-Capable Transport (ECT): 1
.... ...1 = ECN-CE: 1
Total Length: 349
Identification: 0x0000 (0)
Flags: 0x00
0... = Reserved bit: Not set
.0.. = Don't fragment: Not set
..0. = More fragments: Not set
Fragment offset: 0
Time to live: 16
Protocol: UDP (0x11)
Header checksum: 0x6966 (correct)
Source: 24.35.40.1 (24.35.40.1)
Destination: 255.255.255.255 (255.255.255.255)
User Datagram Protocol, Src Port: bootps (67), Dst Port: bootpc (68)
Source port: bootps (67)
Destination port: bootpc (68)
Length: 329
Checksum: 0x6b77 (correct)
Bootstrap Protocol
Message type: Boot Reply (2)
Hardware type: Ethernet
Hardware address length: 6
Hops: 0
Transaction ID: 0x0033d1a0
Seconds elapsed: 0
Bootp flags: 0x8000 (Broadcast)
1... .... .... .... = Broadcast flag: Broadcast
.000 0000 0000 0000 = Reserved flags: 0x0000
Client IP address: 0.0.0.0 (0.0.0.0)
Your (client) IP address: 24.35.42.93 (24.35.42.93)
Next server IP address: 0.0.0.0 (0.0.0.0)
Relay agent IP address: 24.35.40.1 (24.35.40.1)
Client MAC address: 00:12:17:32:ea:79 (Cisco-Li_32:ea:79)
Server host name not given
Boot file name not given
Magic cookie: (OK)
Option 53: DHCP Message Type = DHCP Offer
Option 54: Server Identifier = 24.35.0.42
Option 51: IP Address Lease Time = 6 days, 23 hours, 59 minutes, 55 seconds
Option 1: Subnet Mask = 255.255.248.0
Option 5: Name Server
IP Address: 24.35.0.12
IP Address: 24.35.0.13
Option 23: Default IP Time-to-Live = 64
Option 27: All Subnets are Local = No
Option 28: Broadcast Address = 255.255.255.255
Option 31: Perform Router Discover = Enabled
Option 35: ARP Cache Timeout = 1 minute
Option 37: TCP Default TTL = 64
Option 3: Router = 24.35.40.1
Option 6: Domain Name Server
IP Address: 24.35.0.12
IP Address: 24.35.0.13
Option 44: NetBIOS over TCP/IP Name Server = 127.0.0.1
Option 46: NetBIOS over TCP/IP Node Type = H-node
End Option

"Amadeus W. M." <(E-Mail Removed)> writes:


>They gave me an antique motorolla cable modem, and usually I have a
>linksys router plugged into the router, but right now I have my FC4 pc
>plugged in directly into the modem, to rule out any problems with the
>router.

The router will often work by using dhcp to ask for an address and gateway
for itself, and then deliver and address to you and itself as the gateway
and do NAT for you.
Thus when you transfered to direct connection the ISP, that job fell to your system.

>For the last couple of days the connection was ok, but this afternoon it
>rained, and, since my ISP's service depends on the weather, the network
>went down. If it rains, it goes down, if it's windy, it goes down, if
>there's lightening, you guessed it, it goes down. It's an ISP from hell.

Complain, and complain. There may well be a bad connection somewhere that
is letting in the rain. Does your TV signal also get degraded when it
rains? Ie, it is probably not the ISP but rather hardware.




>Now I've configured eth0 with dhcp. It does get an IP address, but when I
>try to connect anywhere, it says no route to something (I can't check
>exactly what it says right now, because I'm trying to send this).

As you discovered there was no default route. Without a default route,
things will not work. dhcp usually does deliver a default route. And since
it did so when you were connected throught the router, it is not the dhcp
on your system (unless you changed something-- eg the config info in
/etc/sysconfig/network or something)



>I see network activity in gkrellm and I see ARP packets with ethereal,
>so the link is ok. So I look at the routing table, and I see no default
>gateway. But I did see some DHCP packets coming in, so I figured that must
>be the gateway. I do

>route add default gateway xx.xx.xx.xx

>and then voila! I'm online.

Good. You know what the immediate problem is and how to fix it. That is
step 1. Look in the log files in /var/log to see if there are other hints.


>Now that I got this far, I want to pinpoint where the problem is.
>Why am I not getting the default gateway? Is it some bug in my FC4 dhcp
>client, or is my stupid ISP that's not sending it. Is it possible to tell?

>As a matter of fact, I installed the dhcp server on this machine, and my
>other machines as well as the router got all the required info just fine.
>I do want to go out through the router though, and I want it to get all
>the info, as it should. I am positive my hardware is ok, except possibly
>the motorolla cable modem, which is from the ISP.

So what happens when you go through the router?

> So what happens when you go through the router?

Haven't tried yet, but here's the thing. I configure eth0 using
system-config-network (yeah, I'm on FC4) to use dhcp, save, then
stop/start the network. And look at my
/etc/sysconfig/network-scripts/ifcfg-eth0 file:

2) root:~> more /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
BOOTPROTO=dhcp
BROADCAST=192.168.1.255
HWADDR=00:03:6d:13:71:91
IPADDR=192.168.1.10
NETMASK=255.255.255.0
NETWORK=192.168.1.0
ONBOOT=yes
TYPE=Ethernet
DHCP_HOSTNAME=phoenix
USERCTL=no
PEERDNS=yes
GATEWAY=192.168.1.1
IPV6INIT=no

Still trying to use the static private IP and gateway from back when I was
using the router. No, I didn't forget to save the settings. And what's
curious, is that with this file it's still getting the real address
from the ISP (thouth no default gateway).

Yea, during that rain there was a power outage right when I was compiling
some gnome libraries, and sending out several emails and reading news. I
have a surge protector which has a battery and it held up pretty well for
a few minutes, but the power didn't come back until later, so the system
went down uncleanly. I'm beginning to suspect my filesystem/packages have
been corrupted, or my ISP's ARP tables have been poisoned, or I've been
been had. So maybe it's better to reinstall, though I'd be really curious
to see why the network settings are not saved.

"Amadeus W. M." <(E-Mail Removed)> writes:


>> So what happens when you go through the router?

>Haven't tried yet, but here's the thing. I configure eth0 using
>system-config-network (yeah, I'm on FC4) to use dhcp, save, then
>stop/start the network. And look at my
>/etc/sysconfig/network-scripts/ifcfg-eth0 file:

>2) root:~> more /etc/sysconfig/network-scripts/ifcfg-eth0
>DEVICE=eth0
>BOOTPROTO=dhcp
>BROADCAST=192.168.1.255
>HWADDR=00:03:6d:13:71:91
>IPADDR=192.168.1.10
>NETMASK=255.255.255.0
>NETWORK=192.168.1.0
>ONBOOT=yes
>TYPE=Ethernet
>DHCP_HOSTNAME=phoenix
>USERCTL=no
>PEERDNS=yes
>GATEWAY=192.168.1.1
>IPV6INIT=no

???????? Why in the world do you have all that stuff in there? dhcp is for
getting your IP address. Why are you specifying it? Dhcp should give you
your gateway, why are you specifying it.
All you need it the first two lines , onboot, and peerdns
No wonder your system is getting confused.



>Still trying to use the static private IP and gateway from back when I was
>using the router. No, I didn't forget to save the settings. And what's
>curious, is that with this file it's still getting the real address
>from the ISP (thouth no default gateway).

>Yea, during that rain there was a power outage right when I was compiling
>some gnome libraries, and sending out several emails and reading news. I
>have a surge protector which has a battery and it held up pretty well for
>a few minutes, but the power didn't come back until later, so the system
>went down uncleanly. I'm beginning to suspect my filesystem/packages have
>been corrupted, or my ISP's ARP tables have been poisoned, or I've been
>been had. So maybe it's better to reinstall, though I'd be really curious
>to see why the network settings are not saved.

Saved how?

On Wed, 06 Jul 2005 20:48:21 +0000, Unruh wrote:

> "Amadeus W. M." <(E-Mail Removed)> writes:
>
>
>>> So what happens when you go through the router?
>
>>Haven't tried yet, but here's the thing. I configure eth0 using
>>system-config-network (yeah, I'm on FC4) to use dhcp, save, then
>>stop/start the network. And look at my
>>/etc/sysconfig/network-scripts/ifcfg-eth0 file:
>
>>2) root:~> more /etc/sysconfig/network-scripts/ifcfg-eth0
>>DEVICE=eth0
>>BOOTPROTO=dhcp
>>BROADCAST=192.168.1.255
>>HWADDR=00:03:6d:13:71:91
>>IPADDR=192.168.1.10
>>NETMASK=255.255.255.0
>>NETWORK=192.168.1.0
>>ONBOOT=yes
>>TYPE=Ethernet
>>DHCP_HOSTNAME=phoenix
>>USERCTL=no
>>PEERDNS=yes
>>GATEWAY=192.168.1.1
>>IPV6INIT=no
>
> ???????? Why in the world do you have all that stuff in there? dhcp is for
> getting your IP address. Why are you specifying it? Dhcp should give you
> your gateway, why are you specifying it.
> All you need it the first two lines , onboot, and peerdns
> No wonder your system is getting confused.
>

I didn't put any of that in there manually (i.e. with a text editor). In
RH/FC, there is this gui for configuring the network
(system-config-network) which writes out the usual network scripts in
/etc/sysconfig, based on the user selections. So instead of writing out an
ifcfg-eth0 with the dhcp settings, it would write out the above
ifcfg-eth0, no matter what. Probably a gnome thing, due to unclean
shutdown. I reinstalled and it works now. I wouldn't dare touch the
settings though.