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network configuration problem - dumb device on eth0 [message #1754]

Wed, 22 February 2006 12:29

mamos
Messages: 2
Registered: February 2006

Junior Member

hello all,

situation - general overview:

machine with ovzkernel, two devices (eth0 public IP, eth1 private = 192.168.1.0/24) - act as a GW to the net with NAT support. I want to have one/two VPS for development purpose with private IP. eth0 is connected to cable modem.

The problem follow:
# vzctl set 1001 --ipadd 192.168.1.100

behind vzctl is a small piece of script /usr/lib/vzctl/scripts/vps-net_add

from which I can see this error:

arpsend: 192.168.1.100 is detected on another computer : 00:0e:39:d0:20:70
vps-net_add WARNING: arpsend -c 1 -w 1 -D -e 192.168.1.100 eth0 FAILED

it's because the script is doing arpsend for every device which is NOT in "LOOPBACK|NOARP|SLAVE" statups

for DEV in $NETDEVICES; do
${ARPSEND_CMD} ..................
done

NETDEVICEs are detected by
ip link list | egrep -v -E "LOOPBACK|NOARP|SLAVE" | awk "/^[0-9].*:/&&/UP/ {print substr(\$2, 0, length(\$2)-1)}"

The root cause of this problem is a cable modem on the public side (MAC 00:0e:39:d0:20:70). This modem reply to every arpsend comming from eth0 with his MAC addr.

the arp table:
? (192.168.1.101) at * PERM PUP on eth1
? (192.168.1.101) at * PERM PUP on eth0

and routing table:
Destination Gateway Genmask Flags Metric Ref Use Iface
192.168.1.101 0.0.0.0 255.255.255.255 UH 0 0 0 venet0
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth1
pub-net 0.0.0.0 255.255.240.0 U 0 0 0 eth0
169.254.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth1
0.0.0.0 pub-net-gw 0.0.0.0 UG 0 0 0 eth0

Any tips how to fix this issue before I will try to modify the startup script? Razz

thank you for and hint with this very specific problem.

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Re: network configuration problem - dumb device on eth0 [message #1755 is a reply to message #1754]

Wed, 22 February 2006 12:49

dim
Messages: 344
Registered: August 2005

Senior Member

I think the best choice is to modify script and comment out above check or exclude eth0 from list. Rolling Eyes

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Re: network configuration problem - dumb device on eth0 [message #1846 is a reply to message #1755]

Tue, 28 February 2006 21:13

Martijn
Messages: 9
Registered: December 2005
Location: The Netherlands

Junior Member

dim wrote on Wed, 22 February 2006 07:49

I think the best choice is to modify script and comment out above check or exclude eth0 from list. Rolling Eyes

It seems that the cable modem has a "proxy-arp" feature turned on. Dim's solution is a workaround but can't you change the settings in your cable modem maybe? That way you don't need to alter standard scripts of settings.

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Re: network configuration problem - dumb device on eth0 [message #1849 is a reply to message #1846]

Wed, 01 March 2006 06:43

mamos
Messages: 2
Registered: February 2006

Junior Member

I'm sorry, but I can't change any settings. This modem belongs to the cable internet company and also I dont have any passwords for that modem.

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