Topic: Can a PC in my LAN with duplicate IP kill my SME.6 box?

[albatroz]

Yesterday some my SME Box acting as a Gateway stopped working and when tried to restart it -thought that it could help- it also restrated with errors.

Later after reading messagges and boot log
I did find a reference to duplicate IP, so eth0 couldn´t be assigned its respective IP.

Does it seems that someone stupid in my network put
a duplicate IP in my network and this spoiled everything?

I suposse that when someone puts such duplicate IP and error message should appear in SME's screen, as it should be a Kernel message, if such was the case,  where is it saved?

[pietdejong]

I had the same problem a while ago.
When you do an ifcondig, are eth0 and eth1  both UP ?

My experience was that the interface would be shut-down.

[psdata]

Hello albatroz

Yes A duplicate IP can disturp all working IP-trafic.

That's why System admin's trie's to disable that user's can change their network settings's. Thats al so a reasan why sys/net admin's alway's tries to dispatch unused ethernet outlet's in de building becouse if somebody want be evil he can whith his laptop are other funny ip device disturb you hole network.

Sometime's sytems admin's make their one mistake to make the DHCP scope (range) to big so one in de 255 time's he get's a error whith duplicate IP.

Grtz

John

[Tino]

Hi there,

there are two scenarious:

1. Static IP adressing
If statis IP addressing has been implemented, the changes that the first computer which started up the a specific IP address will loose that IP address bacause another pc started up with the same IP addr. is almost impossible, infact it is impossible. The 2nd system will fail to connect with the duplicated IP address and will require that the IP be changed to a non conflicting address before it will connect to the network.

2. Dynanim IP Addressing:
Admin will genenrally allocate a certain range of IP addresses for DHCP to allocate to connecting client. These allocations are generally reserved for 3 days, before DHCP will release the IP address into the allocated IP pool. Consider the DHCP allocated IP range of IP addresses as "private" IP addresses for DHCP.
Any device connecting, with IP, to the network can have a static IP addresses, eventhough DHCP is running. Should one of the DHCP reserved IP addresses be used as a static IP address, DHCP will refuse the connection to the network. You will be forced, by DHCP, to allocate an IP address, to a device, that does not fall within the DHCP allocated IP Range.


Regards,

Tino

[albatroz]

My final question is, isn´t it supossed that such errors
(e.g. "duplicate ip on mac address.. etc")
should be logged in the kernel log?