ping finds server from laptop, but not laptop from server!

ping finds server from laptop, but not laptop from server!

Post by H. Hudso » Tue, 25 Jun 2002 09:07:45



Hi,

Would much appreciate your advice:
ping contacts laptop from server, but laptop fails to ping server!
My problem is getting a laptop under Mdk 8.1 and PCMCIA package
to talk to a connected server PC under Mdk8.2 as a member of a local
intranet.

The server has two ethernet cards, eth1 connected to the PCMCIA card of the
laptop by thin ethernet (with terminators) and eth0 (connects to an Alcatel
ADSL modem, but ADSL is not up for any of the tests described below).

Note below results listed for contacting the laptop from the server:
1. when eth0 was configured for DHCP on IP 192.168.0.1;
2. when eth0 was configured to be manual on IP 192.168.0.1.
In case  1 ping to the laptop 192.168.0.31 is successful,
in case 2 unsuccessful.
In either case the server cannot be pinged successfully from the laptop.
(The manual configuration was a bad idea, ADSL then claims to connect
but does not resolve).

1.
# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:E0:29:11:C3:69
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:2001 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1994 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100
          RX bytes:685403 (669.3 Kb)  TX bytes:91672 (89.5 Kb)
          Interrupt:10 Base address:0x1000

eth1      Link encap:Ethernet  HWaddr 00:00:F8:02:4F:0A
          inet addr:192.168.0.11  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:158 errors:0 dropped:0 overruns:0 frame:0
          TX packets:158 errors:162 dropped:0 overruns:0 carrier:327
          collisions:0 txqueuelen:100
          RX bytes:21569 (21.0 Kb)  TX bytes:21551 (21.0 Kb)
          Interrupt:15 Base address:0x1080

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:429 errors:0 dropped:0 overruns:0 frame:0
          TX packets:429 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:56608 (55.2 Kb)  TX bytes:56608 (55.2 Kb)

ppp0      Link encap:Point-to-Point Protocol
          inet addr:144.137.124.151  P-t-P:172.31.26.24  
Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1492  Metric:1
          RX packets:562 errors:0 dropped:0 overruns:0 frame:0
          TX packets:556 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:3
          RX bytes:586638 (572.8 Kb)  TX bytes:36251 (35.4 Kb)

# more /etc/sysconfig/network-scripts/ifcfg-eth1
DEVICE=eth1
BOOTPROTO=static
IPADDR=192.168.0.11
NETMASK=255.255.255.0
NETWORK=192.168.0.0
BROADCAST=192.168.0.255
ONBOOT=yes
#
DEVICE=eth0
BOOTPROTO=dhcp
IPADDR=192.168.0.1
NETMASK=255.255.255.0
NETWORK=192.168.0.0
BROADCAST=192.168.0.255
ONBOOT=yes
# 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 eth1
127.0.0.0       *               255.0.0.0       U     0      0        0 lo

[ping contact is established to 192.168.0.31, from 192.168.0.11]

2.
After changing 192.168.0.1 from eth0 from dhcp to manual by NetConf and
logging
on again, the following results
# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:E0:29:11:C3:69
          inet addr:192.168.0.1  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:8 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100
          RX bytes:0 (0.0 b)  TX bytes:336 (336.0 b)
          Interrupt:10 Base address:0x1000

eth1      Link encap:Ethernet  HWaddr 00:00:F8:02:4F:0A
          inet addr:192.168.0.11  Bcast:192.168.0.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1226 errors:0 dropped:0 overruns:0 frame:0
          TX packets:1092 errors:6 dropped:0 overruns:0 carrier:15
          collisions:0 txqueuelen:100
          RX bytes:165395 (161.5 Kb)  TX bytes:148213 (144.7 Kb)
          Interrupt:15 Base address:0x1080

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:4456 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4456 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:312155 (304.8 Kb)  TX bytes:312155 (304.8 Kb)

# cd /etc
# ping 192.168.0.1
PING 192.168.0.1 (192.168.0.1) from 192.168.0.1 : 56(84) bytes of data.
64 bytes from 192.168.0.1: icmp_seq=0 ttl=255 time=210 usec
64 bytes from 192.168.0.1: icmp_seq=1 ttl=255 time=132 usec
64 bytes from 192.168.0.1: icmp_seq=2 ttl=255 time=127 usec

--- 192.168.0.1 ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max/mdev = 0.127/0.156/0.210/0.039 ms

PING 192.168.0.31 (192.168.0.31) from 192.168.0.1 : 56(84) bytes of data.
From 192.168.0.1: Destination Host Unreachable
From 192.168.0.1: Destination Host Unreachable
From 192.168.0.1: Destination Host Unreachable
From 192.168.0.1: Destination Host Unreachable
From 192.168.0.1: Destination Host Unreachable
From 192.168.0.1: Destination Host Unreachable

--- 192.168.0.31 ping statistics ---
8 packets transmitted, 0 packets received, +6 errors, 100% packet loss
# 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
192.168.0.0     *               255.255.255.0   U     0      0        0 eth0
127.0.0.0       *               255.0.0.0       U     0      0        0 lo
#  more /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE="eth0"
BOOTPROTO="none"
IPADDR="192.168.0.1"
NETMASK="255.255.255.0"
NETWORK=192.168.0.0
BROADCAST=192.168.0.255
ONBOOT="yes"
IPXNETNUM_802_2=""
IPXPRIMARY_802_2="no"
IPXACTIVE_802_2="no"
IPXNETNUM_802_3=""
IPXPRIMARY_802_3="no"
IPXACTIVE_802_3="no"
IPXNETNUM_ETHERII=""
IPXPRIMARY_ETHERII="no"
IPXACTIVE_ETHERII="no"
IPXNETNUM_SNAP=""

# ping 192.168.0.11
PING 192.168.0.11 (192.168.0.11) from 192.168.0.11 : 56(84) bytes of data.
64 bytes from 192.168.0.11: icmp_seq=0 ttl=255 time=210 usec
64 bytes from 192.168.0.11: icmp_seq=1 ttl=255 time=128 usec
64 bytes from 192.168.0.11: icmp_seq=2 ttl=255 time=128 usec
64 bytes from 192.168.0.11: icmp_seq=3 ttl=255 time=128 usec
64 bytes from 192.168.0.11: icmp_seq=4 ttl=255 time=127 usec

--- 192.168.0.11 ping statistics ---
5 packets transmitted, 5 packets received, 0% packet loss
round-trip min/avg/max/mdev = 0.127/0.144/0.210/0.033 ms
IPXPRIMARY_SNAP="no"
IPXACTIVE_SNAP="no"

--
H. Hudson
Sydney, Australia

 
 
 

ping finds server from laptop, but not laptop from server!

Post by steve housem » Tue, 25 Jun 2002 20:07:57


the second eth0 reveals it is the same net as eth1 ...
The routing code looks at the destination of each packet
and decides which interface to use based on that ....
so it will be confused if both on same net                    
They need to be on separate nets eg

eth1      Link encap:Ethernet  HWaddr 00:00:F8:02:4F:0A
          inet addr:192.168.1.11  Bcast:192.168.1.255  Mask:255.255.255.0
                            ^                   ^
          etc                                                    

also the first eth1 ifconfig shows high error rate  which may
indicate a bad hardware connection or an  interrupt clash ...
cat /proc/interrupts
might reveal something ... 15 is ide1 on my system.

The dhcp stuff shows identical info so dhcp is not the problem.

The other useful tool is tcpdump which if run on both machines for
their interconnection interface, should show arp requests and
responses flowing between them prior to the first ping request,
and occasionally thereafter.

Hope you fix it soon,

Steve Houseman

--

currently  steve at houseman demon co uk

 
 
 

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