Question on Automatic Failover/Failback on Linux

richinsc · 12-05-2008, 06:19 PM

I wanted to know if there is a way to have dual interfaces on a server do failover and failback for the interfaces. In the example below I am trying to make a network as redundant as possible. If I have a server that has two interfaces I want to make sure that it will still be accessible should one of the core switches die. The OS is Debian. Bridging, Teaming, and Multicast Routing won't work because the interfaces are connected to to completely different switches. I am also trying to figure out how to do this since I am trying to keep from installing a load balancing gateway but if possible, need both interfaces to have the same ip, but only one may be active at a time. I don't need the server itself to do load balancing, how ever it would be a nice add on.

Code:

*---------------*
*    Router	* ------------------------------------------------------
*---------------*		|					|
				|					|
				|					|
			    *-------*				    *------*
			    *	FW1 *------------Failover-----------*  FW2 *
			    *-------*				    *------*
				|					|
				|					|
				|					|
				|					|
			+---------------+			+---------------+
			+   Core SW1	+			+   Core SW2	+
			+---------------+			+---------------+
				\					/
				 \				       /
				  \				      /
				   \				     /
				    \				    /
				     \			 	   /
				      \				  /
				       \			 /
					\			/
					 \		       /
					  \		      /
					   \		     /
					    \		    /
					     \		   /
					      \		  /
					       \	 /
						\	/
					     	eth0  eth1
					   +----------------+
					   +	Server1     +
					   +----------------+

BrianK · 12-05-2008, 08:03 PM

It can be done with bonding. You want "High Availability" bonding with multiple switches.

http://www.linuxfoundation.org/en/Net:Bonding

richinsc · 12-06-2008, 04:36 PM

Well after a day of trying and also realizing that my network won't allow for the setup above. I decided to setup boding to just one switch. But after configuring boding successfully I am unable in Debian Etch AMD64 able to get mode to change from balance-rr(0) to 802.3ad(4). I have tried setting to mode=4 and no success. I have also tired to put configuration in following paths and it still defaults back to balance-rr.

Configured in

/etc/modprobe.d/aliases
/etc/modprobe.d/bond0
/etc/modprobe.d/aliases-bond
/etc/modutils/aliases
/etc/modutils/arch/i386
/etc/modutils/arch/x86_64

in /etc/modules I added "bonding" to file

and then in each of the files above I tried putting following

Code:

alias bond0 bonding
options bonding mode=4 arp_interval=60 arp_ip_target=xxx.xxx.xxx.xxx,xxx.xxx.xxx.xxx

this is what shows up in /proc/net/bonding/bond0

Code:

Ethernet Channel Bonding Driver: v3.0.3 (March 23, 2006)

Bonding Mode: load balancing (round-robin)