weird network problem in FC4
Paul Howarth
paul at city-fan.org
Wed Jul 6 06:46:49 UTC 2005
On Wed, 2005-07-06 at 01:02 -0400, Amadeus W. M. wrote:
> 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 seems to depend 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 network unreachable:
>
> ssh: connect to host cse port 22: Network is unreachable
>
> 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:
>
> 12) root:~> route -n
> Kernel IP routing table
> Destination Gateway Genmask Flags Metric Ref Use Iface
> 24.35.40.0 0.0.0.0 255.255.248.0 U 0 0 0 eth0
> 169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth0
>
> I have absolutely no idea where the 168.254.0.0 came from. I did see this
> happening in windows, a long time ago. All I did in the network
> configuration tool was to click on get IP automatically with dhcp.
>
> Anyway, I did see some DHCP packets with ethereal coming in, among
> countless ARP packets (Who has xxx, Tell yyy), so I figured that must be
> the gateway. Manually, 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?
>
> For what it's worth, I installed the dhcp server on this machine (FC2,
> just prior to FC4), 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
---------------^^^^^^^^^^^^^^^^^^^^
That looks like the setting for the default gateway to me.
> 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
Paul.
--
Paul Howarth <paul at city-fan.org>
More information about the fedora-list
mailing list