DHCP ok but can't ping

ropbo · 08-19-2004, 11:17 PM

Hi all,

I'm newbie to Linux and that's my first post.

First I tried to find any other posts on the same issue, googled it around for a while but haven't found anything that could've helped me so, here I am.

I have the following scenario ( simple one by the way ):

10.0.0.0---(eth1).Linux Box.(eth0) ---216.x.y.0

I hoop up my Powerbook to eth1 ( inside adapter ) and get an IP from the DHCP. Fine.

Problem is: I can't ping it. Odd. And I can't ping my laptop from the Linux box.

I also tried to ssh it ( that's my only TCP port open - 22 ) because firstly I suspected there was something blocking ICMP packets and stuff, but also got : "host is down" or something ( don't remember exactly )

Some tests from my box:

g4:~ rodrigo$ ifconfig
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
inet6 ::1 prefixlen 128
inet6 fe80::1 prefixlen 64 scopeid 0x1
inet 127.0.0.1 netmask 0xff000000

en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
inet6 fe80::20d:93ff:fec3:7a74 prefixlen 64 scopeid 0x4
inet 10.0.0.10 netmask 0xffffff00 broadcast 10.0.0.255
ether 00:0d:93:c3:7a:74
media: autoselect (10baseT/UTP <half-duplex>) status: active

g4:~ rodrigo$ ping 10.0.0.1
PING 10.0.0.1 (10.0.0.1): 56 data bytes
ping: sendto: Host is down
ping: wrote 10.0.0.1 64 chars, ret=-1
ping: sendto: Host is down
ping: wrote 10.0.0.1 64 chars, ret=-1
ping: sendto: Host is down
ping: wrote 10.0.0.1 64 chars, ret=-1
ping: sendto: Host is down

g4:~ rodrigo$ arp -a
? (10.0.0.1) at (incomplete) on en0 [ethernet]
? (10.0.0.255) at ff:ff:ff:ff:ff:ff on en0 [ethernet]

g4:~ rodrigo$ ping 10.0.0.255
PING 10.0.0.255 (10.0.0.255): 56 data bytes
64 bytes from 10.0.0.10: icmp_seq=0 ttl=64 time=0.204 ms
64 bytes from 10.0.0.1: icmp_seq=0 ttl=255 time=16.544 ms (DUP!)
64 bytes from 10.0.0.10: icmp_seq=1 ttl=64 time=0.215 ms
64 bytes from 10.0.0.1: icmp_seq=1 ttl=255 time=1.652 ms (DUP!)

Duplicated packets ... weird ...

g4:~ rodrigo$ arp -a
? (10.0.0.1) at (incomplete) on en0 [ethernet]
? (10.0.0.255) at ff:ff:ff:ff:ff:ff on en0 [ethernet]

I also tried with a Windows box and got the same results.

From the Linux box ( the server ):

Linux debian 2.4.18 #4 SMP Tue Aug 17 04:42:59 PDT 2004 i586 unknown

debian:/home/rodrigo# route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
216.x.y.0 * 255.255.255.128 U 0 0 0 eth0
10.0.0.0 * 255.255.255.0 U 0 0 0 eth1
default 216-x-y-1.ip 0.0.0.0 UG 0 0 0 eth0

The interesting thing is that before I upgrade the kernel from 2.2.x to 2.4.18, I could ping. After the upgrade, not anymore.

.config that I used to compile the new kernel ( skipped some parts ):

# Networking options
#
CONFIG_PACKET=m
CONFIG_PACKET_MMAP=y
CONFIG_NETLINK_DEV=m
CONFIG_NETFILTER=y
CONFIG_NETFILTER_DEBUG=y
CONFIG_FILTER=y
CONFIG_UNIX=y
CONFIG_INET=y
CONFIG_IP_MULTICAST=y
# CONFIG_IP_ADVANCED_ROUTER is not set
# CONFIG_IP_PNP is not set
CONFIG_NET_IPIP=m
# CONFIG_NET_IPGRE is not set
# CONFIG_IP_MROUTE is not set
# CONFIG_ARPD is not set
# CONFIG_INET_ECN is not set
CONFIG_SYN_COOKIES=y

# IP: Netfilter Configuration
#
CONFIG_IP_NF_CONNTRACK=m
CONFIG_IP_NF_FTP=m
CONFIG_IP_NF_IRC=m
CONFIG_IP_NF_QUEUE=m
CONFIG_IP_NF_IPTABLES=m
CONFIG_IP_NF_MATCH_LIMIT=m
CONFIG_IP_NF_MATCH_MAC=m
CONFIG_IP_NF_MATCH_MARK=m
CONFIG_IP_NF_MATCH_MULTIPORT=m
# CONFIG_IP_NF_MATCH_TOS is not set
# CONFIG_IP_NF_MATCH_AH_ESP is not set
# CONFIG_IP_NF_MATCH_LENGTH is not set
# CONFIG_IP_NF_MATCH_TTL is not set
CONFIG_IP_NF_MATCH_TCPMSS=m
CONFIG_IP_NF_MATCH_STATE=m
CONFIG_IP_NF_MATCH_UNCLEAN=m
CONFIG_IP_NF_MATCH_OWNER=m
CONFIG_IP_NF_FILTER=m
CONFIG_IP_NF_TARGET_REJECT=m
# CONFIG_IP_NF_TARGET_MIRROR is not set
CONFIG_IP_NF_NAT=m
CONFIG_IP_NF_NAT_NEEDED=y

CONFIG_IP_NF_TARGET_MASQUERADE=m
# CONFIG_IP_NF_TARGET_REDIRECT is not set
# CONFIG_IP_NF_NAT_SNMP_BASIC is not set
CONFIG_IP_NF_NAT_IRC=m
CONFIG_IP_NF_NAT_FTP=m
CONFIG_IP_NF_MANGLE=m
# CONFIG_IP_NF_TARGET_TOS is not set
CONFIG_IP_NF_TARGET_MARK=m
CONFIG_IP_NF_TARGET_LOG=m
# CONFIG_IP_NF_TARGET_ULOG is not set
CONFIG_IP_NF_TARGET_TCPMSS=m
CONFIG_IP_NF_COMPAT_IPCHAINS=m
CONFIG_IP_NF_NAT_NEEDED=y
CONFIG_IP_NF_COMPAT_IPFWADM=m
CONFIG_IP_NF_NAT_NEEDED=y
# CONFIG_IPV6 is not set
# CONFIG_KHTTPD is not set
# CONFIG_ATM is not set
# CONFIG_VLAN_8021Q is not set
# CONFIG_IPX is not set
# CONFIG_ATALK is not set
# CONFIG_DECNET is not set
# CONFIG_BRIDGE is not set
# CONFIG_X25 is not set
# CONFIG_LAPB is not set
# CONFIG_LLC is not set
# CONFIG_NET_DIVERT is not set
# CONFIG_ECONET is not set
# CONFIG_WAN_ROUTER is not set
# CONFIG_NET_FASTROUTE is not set
# CONFIG_NET_HW_FLOWCONTROL is not set

Tried to ping my box from the Linux box. Nothing.

debian:/home/rodrigo# arp -n -i eth1
Address HWtype HWaddress Flags Mask iFace
10.0.0.10 ether 00:0D:93:C3:7A:74 C eth1

debian:/home/rodrigo# arp -a -i eth1
? ( 10.0.0.10 ) at 00:0D:93:C3:7A:74 [ether] on eth1

Sorry for the long email.

Any ideas ?

Rodrigo Otavio Paes de Barros Otaviano

joesmack · 08-20-2004, 12:04 AM

Your inet for en0 is 10.0.0.10 so why are you pinging 10.0.0.1?

ropbo · 08-20-2004, 12:06 AM

my box -> 10.0.0.10
linux box -> 10.0.0.1

I'm trying to ping the Linux box from my laptop and get nothing. I also tried to ping my laptop from the server. Got nothing as well.

Rodrigo Otavio Paes de Barros Otaviano

Lentil · 09-05-2004, 10:11 PM

I have a very similar problem.

I did a basic install using the Debian-woody stable dist, which installs the 2.2.20 kernel.

With this kernel, DHCP and networking work perfectly. Ping, web, router displays the box as connected... etc.

I installed a new custom kernal based on the 2.4.19 source in the stable dist (added sound and removed other stuff).

Now, the DHCP does not appear to be working. I believe I did not include DHCP in the kernel, my understanding is that normally this is handled by the software after the kernel boots. Pinging localhost still works (duh!).

If I configure eth0 manually using a static address and netmask (using ifconfig) and setup a default route to my router (which is the DHCP server), networking works as expected. My router does not display the box as connected.

I checked my /etc/network/interfaces:

Code:

auto lo
iface lo inet loopback
auto eth0
iface eth0 inet dhcp

dhcp-client package is installed. dhcpd (server) is NOT installed although I'm trying that now just in case it matters.

The 'NIC' is a mobo-builtin Intel jobber (i82557).

ropbo · 09-05-2004, 10:31 PM

Hum, in my case the DHCP server was working after the upgrade and the client was ditching IPs normally but I couldn't ping the gateway. Very weird situation.

But I got it solved. The problem was my Intel EtherExpress 16. So I replaced with a 3Com and it worked like a charm.

In your case, you may want to use /etc/default/dhcp to declare the interface dhcpd should listen to. /etc/init.d/dhcp reads this file first.

Rodrigo Otavio Paes de Barros Otaviano

Lentil · 09-06-2004, 08:37 AM

I don't have a file at /etc/defaults/dhcp

I was looking in the /var/log/syslog and noticed that for 2.2.20-idepci the DHCP client runs correctly.

For my 2.4.19 kernel, I'm getting an error that says 'make sure that CONFIG_PACKET and CONFIG_FILTER' are defined in your kernel'

CONFIG_PACKET=y

but

CONFIG_FILTER is not set

So let me try that.

Lentil · 09-06-2004, 10:02 AM

That did the trick.

The description provided in make xconfig doesn't imply that this should be required for DHCP... but that did the trick.

Now on to my soundcard debugging...