From mboxrd@z Thu Jan 1 00:00:00 1970 From: Manish Kathuria Date: Thu, 26 Jan 2006 13:41:18 +0000 Subject: [LARTC] Problems in Dead Gateway Detection / Failover - Multiple Message-Id: <43D8CEAE.3010006@tuxspace.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lartc@vger.kernel.org Hello, I have configured a load balancing router using Julian's patches and as described in "nano.txt" for two ISP links as shown below. ISP 1 ISP 2 . . | | | | | | | WAN WAN | +-\-+ +-\-+ | | | | |R1 | GW1 GW2 |R2 | | |------. --------| | | | | | | | +---+ | | +---+ EXT1 | | EXT2 +\----\-+ | | | LINUX | | ROUTER| | | | | | | +---/---+ | INT IF | | | /----------------\ | LAN | | | \----------------/ LAN NETWORK = 192.168.100.0/24 INT IF = 192.168.100.1 ISP1 NETWORK = 10.20.30.128/29 R1 - ROUTER1 GW1 = 10.20.30.129 EXT1 = 10.20.30.130 ISP2 NETWORK = 172.16.32.128/29 R2 - ROUTER2 GW2 = 172.16.32.129 EXT2 = 172.16.32.130 Both the ISPs have provided /29 subnets of Public IPs. The above mentioned addresses are just for example. The gateways for both the ISPs are routers placed at the same location which are further connected through Radio Link and Leased Line. Things work fine as long as both the ISP links are alive. While testing the dead gateway detection and failover functionality we observed that if we make the first hop gateway (i.e Router R1 or R2) of one of the ISPs dead by either disconnecting the ethernet cable between Linux Router and R1/R2 or by switching off the gateway (R1/R2) itself, dead gateway detection takes place and failover to the other ISP takes place. However, if there is a problem in the ISP connectivity at any of the subsequent hops, there is no dead gateway detection and failover also does not take place. I have tested this on various linux kernels from 2.4 as well as 2.6 series. Somehow I have never faced a similar problem before and things have been working perfectly. In real life situation here, the first hop gateway is rarely going to be down so dead gateway detection and failover is going to be required whenever there is some connectivity problem at any of the later hops. So that's where dead gateway detection needs to work. What could be the reason ? How can this be resolved ? I would appreciate any pointers or suggestions. Thanks, Manish Kathuria _______________________________________________ LARTC mailing list LARTC@mailman.ds9a.nl http://mailman.ds9a.nl/cgi-bin/mailman/listinfo/lartc