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Subject
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UML (UserModeLinux) networking problem
- 11-07-2003
- G. Neumann
November 7, 2003, 2:10 pm

Hi Linuxers,
sorry to post this in 3 different news-groups, but I have no clou
which group would be the right one to ask.
I have a problem with UML and networking.
I try to setup a network connection between the UML virtuel machine
and the host but I don't get connection between them.
I can configure the eth0 device within UML using ifconfig and
I see the tap-device on the host. Seems to me, that the UML helper
programs (like uml_net) are working.
Both interfaces (UML and host) are up and routes are configured to the
devices with the apropriate network-addresses.
If I start tcpdump on both 'machines' and try pings between them, I
can see ARP-requests at the origin. But I don't receive any tcpdump
output at the destination and the target is unreachable.
What can I do/check to get the connection working ?
Could there be something missing within the host kernel ?
By the way, yes I know I can mount the host's filesystem on the UML
virual machine, but this is not what I want or need. I need the
possibility to initiate commands (e.g. via rsh) at the UML machine
from the/a host.
Any help/suggestion is welcome.
Thanks in advance
Guenter
The facts:
host-kernel: linux 2.4.18
UML-kernel: user_mode_linux-2.4.18.36um-0
executable downloaded form UML homepage (rpm package)
command on host: ping 192.169.10.10
command on UML: ping 192.168.10.100
ifconfig from host:
-------------------
eth0 Link encap:Ethernet HWaddr 00:04:76:EA:99:46
inet addr:129.23.12.160 Bcast:129.23.15.255 Mask:255.255.252.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:5969070 errors:0 dropped:0 overruns:81 frame:0
TX packets:6075222 errors:0 dropped:0 overruns:0 carrier:0
collisions:691821 txqueuelen:100
RX bytes:2746909112 (2619.6 Mb) TX bytes:2242485986 (2138.6 Mb)
Interrupt:11 Base address:0x3400
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:21075 errors:0 dropped:0 overruns:0 frame:0
TX packets:21075 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:1602048 (1.5 Mb) TX bytes:1602048 (1.5 Mb)
tap0 Link encap:Ethernet HWaddr FE:FD:00:00:00:00
inet addr:192.168.10.100 Bcast:192.168.10.255
Mask:255.255.255.255
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:148 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:17840 (17.4 Kb)
Interrupt:5
ifconfig from UML:
------------------
eth0 Link encap:Ethernet HWaddr FE:FD:C0:A8:0A:0A
inet addr:192.168.10.10 Bcast:192.168.10.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1484 Metric:1
RX packets:1 errors:0 dropped:0 overruns:0 frame:0
TX packets:6 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:28 (28.0 b) TX bytes:264 (264.0 b)
Interrupt:5
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:18 errors:0 dropped:0 overruns:0 frame:0
TX packets:18 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:1628 (1.5 Kb) TX bytes:1628 (1.5 Kb)
route from host:
----------------
Destination Gateway Genmask Flags Metric Ref Use
Iface
192.168.10.0 * 255.255.255.0 U 0 0 0 tap0
mchm_32 * 255.255.252.0 U 0 0 0 eth0
loopback * 255.0.0.0 U 0 0 0 lo
default mmma.ma. 0.0.0.0 UG 0 0 0 eth0
route from UML:
---------------
Destination Gateway Genmask Flags Metric Ref Use
Iface
192.168.10.0 * 255.255.255.0 U 0 0 0 eth0
sorry to post this in 3 different news-groups, but I have no clou
which group would be the right one to ask.
I have a problem with UML and networking.
I try to setup a network connection between the UML virtuel machine
and the host but I don't get connection between them.
I can configure the eth0 device within UML using ifconfig and
I see the tap-device on the host. Seems to me, that the UML helper
programs (like uml_net) are working.
Both interfaces (UML and host) are up and routes are configured to the
devices with the apropriate network-addresses.
If I start tcpdump on both 'machines' and try pings between them, I
can see ARP-requests at the origin. But I don't receive any tcpdump
output at the destination and the target is unreachable.
What can I do/check to get the connection working ?
Could there be something missing within the host kernel ?
By the way, yes I know I can mount the host's filesystem on the UML
virual machine, but this is not what I want or need. I need the
possibility to initiate commands (e.g. via rsh) at the UML machine
from the/a host.
Any help/suggestion is welcome.
Thanks in advance
Guenter
The facts:
host-kernel: linux 2.4.18
UML-kernel: user_mode_linux-2.4.18.36um-0
executable downloaded form UML homepage (rpm package)
command on host: ping 192.169.10.10
command on UML: ping 192.168.10.100
ifconfig from host:
-------------------
eth0 Link encap:Ethernet HWaddr 00:04:76:EA:99:46
inet addr:129.23.12.160 Bcast:129.23.15.255 Mask:255.255.252.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:5969070 errors:0 dropped:0 overruns:81 frame:0
TX packets:6075222 errors:0 dropped:0 overruns:0 carrier:0
collisions:691821 txqueuelen:100
RX bytes:2746909112 (2619.6 Mb) TX bytes:2242485986 (2138.6 Mb)
Interrupt:11 Base address:0x3400
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:21075 errors:0 dropped:0 overruns:0 frame:0
TX packets:21075 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:1602048 (1.5 Mb) TX bytes:1602048 (1.5 Mb)
tap0 Link encap:Ethernet HWaddr FE:FD:00:00:00:00
inet addr:192.168.10.100 Bcast:192.168.10.255
Mask:255.255.255.255
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:148 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 b) TX bytes:17840 (17.4 Kb)
Interrupt:5
ifconfig from UML:
------------------
eth0 Link encap:Ethernet HWaddr FE:FD:C0:A8:0A:0A
inet addr:192.168.10.10 Bcast:192.168.10.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1484 Metric:1
RX packets:1 errors:0 dropped:0 overruns:0 frame:0
TX packets:6 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:100
RX bytes:28 (28.0 b) TX bytes:264 (264.0 b)
Interrupt:5
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:18 errors:0 dropped:0 overruns:0 frame:0
TX packets:18 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:1628 (1.5 Kb) TX bytes:1628 (1.5 Kb)
route from host:
----------------
Destination Gateway Genmask Flags Metric Ref Use
Iface
192.168.10.0 * 255.255.255.0 U 0 0 0 tap0
mchm_32 * 255.255.252.0 U 0 0 0 eth0
loopback * 255.0.0.0 U 0 0 0 lo
default mmma.ma. 0.0.0.0 UG 0 0 0 eth0
route from UML:
---------------
Destination Gateway Genmask Flags Metric Ref Use
Iface
192.168.10.0 * 255.255.255.0 U 0 0 0 eth0

Re: UML (UserModeLinux) networking problem

On the 'tap0' interface, the netmask value is specified as
'255.255.255.255'. Try changing the netmask value to '255.255.255.0' and
see if this change fixes the problem.

--
Jim
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Jim
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