[rhelv6-list] Seeing only ONE session/device instead of TWO

[Phil Meyer]

On 04/03/2012 02:16 PM, Prashanth Sundaram wrote:
>
> Hello,
>
> I am having some trouble with ISCSI to work on  RHEL 6.2. It currently 
> is using 1 nic to connect to SAN and shows only 1 session instead of 
> 2. I have configured TWO nics(em3 & em4) to perform multipathing and 
> have verified that both can connect to SAN.
>
> Any ideas how to get multipath to work? I only see 1 device instead of 
> 2 in multipath. Please see my config below.
>
> Another strange thing is that the iface_name has different MAC address 
> than what ifconfig shows.
>
>


Two main issues.

On the same network, two interfaces need to negotiate ARP independently 
of each other.  If not, a packet can exit one interface, and be sent a 
response to another interface.  That does not work.

/etc/sysctl.conf needs to be adjusted for ARP by interface.
Clues:
# net
# net.ipv4.conf.all.arp_filter = 1
# net.ipv4.conf.all.rp_filter = 1
# net.ipv4.conf.default.arp_filter = 1
net.ipv4.conf.all.arp_ignore=1
net.ipv4.conf.all.arp_announce=2

ISCSI needs to be told that there are two interfaces, it does not know 
it by default.

This is done by special files in: /var/lib/iscsi/ifaces

I don't have a sample nearby, but that should get you googleing ok.

Once that is in place, 'iscsiadm -m node -l' will show two logins for 
every target.
If THAT happens, 'multipath -r' will show two connections per device.

Good Luck!