2 IPs of same subnet and one gateway problem

From: G. Berg (gerand_at_firemail.de)
Date: 07/25/03 

Date: Fri, 25 Jul 2003 01:56:36 +0200

Hello!

I have a problem with my Network Configuration in RedHat 9.0!

I have 2 NICs (in case one of them fails or the cabling is not okay...).
They have IPs like 123.123.123.1 AND 123.123.123.2, so they are in the
same subnet. The Gateway for both is 123.123.123.254.

Now I setup Redhat with just one of the cards and everything works fine.
Now I add the second card (BTW a 3COM 3c59x) and load the appropriate
driver. This works well. Now I create a
/etc/sysconfig/network-script/ifcfg-eth1
with nearly the same settings as ifcfg-eth0 (IP-addr. and interface
changed of course).

As soon as I restart the network, just ONE of the NICs is active. The
other one just is not there. The one NIC responds to both IPs.

Then I did it manually:
/etc/rc.d/init.d/network stop
(checked ifconfig... no network up, okay lets go on)

ifconfig eth0 123.123.123.1 up
ifconfig eth1 123.123.123.2 up
route add default gw 123.123.123.254

And: I get the same results as above. Just one NIC responds to both IPs.
Its not always the same. It seems to the NIC which is activeted first.

I crawled through several google search results and got to know that
there are known problems with two IPs in the same subnet. But most of
the articles are due to kernel 2.2.

So do you know what I am missing or where I am going wrong?

Thanks in advance

Relevant Pages

  • Re: Event ID 1000 (Userenv) Error and Event ID 8021 (BROWSER) Error
    ... > destination route entry with the 192.168.0.1 GWY was higher priority, ... > the external network), and from there to the open Internet. ... > An additional item is that it appears that if any of the NICs in the ... > with destination addresses on the 192.168.1 subnet to get to the ...
    (microsoft.public.win2000.dns)
  • Re: Event ID 1000 (Userenv) Error and Event ID 8021 (BROWSER) Error
    ... > destination route entry with the 192.168.0.1 GWY was higher priority, ... > the external network), and from there to the open Internet. ... > An additional item is that it appears that if any of the NICs in the ... > with destination addresses on the 192.168.1 subnet to get to the ...
    (microsoft.public.win2000.networking)
  • Re: Cant seem to get packets to route
    ... 5 usable IPs and broadcast IP. ... > especially when that network overlaps your assigned IP range. ... > the internet as the IP of your internet interface. ... the same /24 subnet. ...
    (comp.os.linux.networking)
  • Re: Default Gateway Reverts to Old Setting
    ... This server is on the only IP subnet at the client's main office. ... The server has two identical 10/100/1000 NICs, ... TCP/IP is the only network protocol installed. ...
    (microsoft.public.windows.server.networking)
  • Re: Using multiple network cards and IP addresses in one machine
    ... I would remove all the network cards but one and use either DNS ... aliases or IIS virtual web sites to handle the multiple site issues. ... What I've got is a web server behind ISA 2004 and that server has two NICs ... the same subnet - each is for a different site. ...
    (microsoft.public.win2000.networking)