In this respect, Linux treats IP addresses in a host-based rather than
interface-based fashion. A Linux host owning a given IP address will respond to
an ARP request for that address on any and all interfaces that receive the
request, supplying the MAC address of the responding interface. This behavior
can be modified by enabling arp_filter for the desired interfaces.
echo 1 > /proc/sys/net/ipv4/conf/<netdev>/arp_filter
Thomas
________________________________
From: linux-poweredge-bounces-Lists On Behalf Of sa
Sent: Wednesday, April 28, 2010 3:35 PM
To: linux-poweredge-Lists
Subject: Question about "host already uses address" on PE r610 with Broadcom
NetXtreme II
I have a pair of Dell r610s, each of which has an on board quad port Broadcom
network card. Both are running a recently patched CentOS 5.4. I set each
server up to use DHCP to get an IP address for eth0. On server 1, I set eth3
to 192.168.253.1. Everything is working as expected. I can access the server
via either address. Note that both ports are connected to the same switch.
Now I physically move the network cord from eth3 on server1 to eth3 on server2.
I turn on server 2 which gets its eth0 address from DHCP. eth3 is set to use
the same IP that eth3 on server1 was, 192.168.253.1. However eth3 on server2
fails to come up, issuing this error:
Error, some other host already uses address 192.168.253.1.
So at this point, I have server1 that only has eth0 physically connected to the
network. I have server2 that has eth0 and eth3 connected to the network. If I
issue an arping 192.168.253.1, I get back the MAC address of eth0 on server1.
Then I do the following steps.
server2 # ifup eth3
Error, some other host already uses address 192.168.253.1.
server1 # ifdown eth3
server1 #
server2 # ifup eth3
server2 #
server2 # ifconfig eth3
eth3 Link encap:Ethernet HWaddr 00:21:9B:99:1B:F2
inet addr:192.168.253.1 Bcast:192.168.253.255 Mask:255.255.255.0
....
server2 # ifdown eth3
server1 # ifup eth3
server2 # ifup eth3
Error, some other host already uses address 192.168.253.1.
Physically disconnect eth0 on server1 while eth3 is configured and eth3 on
server2 comes up with no error.
So my question comes down to how is an interface that is not physically
connected to the network having this effect? Why does the connection to eth0
seem to be influencing the eth3 settings?
Got questions or need more info, let me know.
Chris
---------------------
More info:
server2 # arping 192.168.253.1
Unicast reply from 192.168.253.1 [00:21:9B:99:11:E7] 0.700ms
Unicast reply from 192.168.253.1 [00:21:9B:99:11:E7] 0.682ms
server 1 # ifconfig
eth0 Link encap:Ethernet HWaddr 00:21:9B:99:11:E7
inet addr:10.1.0.189 Bcast:10.1.255.255 Mask:255.255.0.0
...
...
eth3 Link encap:Ethernet HWaddr 00:21:9B:99:11:ED
inet addr:192.168.253.1 Bcast:192.168.253.255 Mask:255.255.255.0
dmesg | grep Bro
Broadcom NetXtreme II Gigabit Ethernet Driver bnx2 v1.9.3 (March 17, 2009)
eth0: Broadcom NetXtreme II BCM5709 1000Base-T (C0) PCI Express found at mem
d6000000, IRQ 90, node addr 00219b9911e7
eth1: Broadcom NetXtreme II BCM5709 1000Base-T (C0) PCI Express found at mem
d8000000, IRQ 98, node addr 00219b9911e9
eth2: Broadcom NetXtreme II BCM5709 1000Base-T (C0) PCI Express found at mem
da000000, IRQ 106, node addr 00219b9911eb
eth3: Broadcom NetXtreme II BCM5709 1000Base-T (C0) PCI Express found at mem
dc000000, IRQ 114, node addr 00219b9911ed
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