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Message-Id: <1176048615.686.78.camel@owl.home.ie> Date: Sun, 08 Apr 2007 17:10:15 +0100 From: W Agtail <wagtail@....ie> To: Lennart Sorensen <lsorense@...lub.uwaterloo.ca> Cc: netdev@...r.kernel.org Subject: Re: two gateways with one NIC Hi, and thanks very much for your response. Your guess sounds spot on. As you've mentioned, using one sync group works quite well and gives you an active/passive LVS cluster (not sure of correct terminology here - sorry), thus all traffic goes via LVS1, leaving LVS2 not doing much unless LVS1 fails. I thought it would be a cool idea to setup two sync groups to ultimately handle several Apache instances on the two Apache servers. This way, both LVS servers would be used in a kind of active/active fashion and would be a master/slave to each other. For example, vip1 & gw1 could possibly end up on LVS2 with vip2 & gw2. The challenge though in having two sync groups, with two GWs. I would like all traffic coming through vip1 to be returned via gw1 and all traffic coming through vip2 to be returned via gw2. I am using keepalived (v1.1.13) with two sync groups. One with vip1 & gw1 and another with vip2 & gw2. Port 8088 will always comes through vip1/gw1, load balancing to web1:8088 and web2:8088. Port 8089 will always come through vip2/gw2, load balancing to web1:8089 and web2:8089. Web1's default gw is set to gw1 and web2's default gw is set to gw2. But this causing issues when say, vip1:8088 gets forwarded through gw1 to web2:8088 and doesn't get back back via gw2. To get round this, I need something like iproute2 on web2 to send all 8088 traffic back through gw1. Hope this makes a little more sense to what I'm trying to achieve? Thanks again. On Sun, 2007-04-08 at 11:01 -0400, Lennart Sorensen wrote: > On Sun, Apr 08, 2007 at 04:35:53AM +0100, W Agtail wrote: > > Hope you can help. > > > > I have the following setup using LVS (Linux Virtual Servers): > > > > LAN--------------------192.168.0.0/24----------------- <= CLIENTS > > | | > > | | > > LVS1 LVS2 > > vip1: 192.168.0.111 vip2: 192.168.0.121 > > eth0: 192.168.0.110 eth0: 192.168.0.120 > > eth1: 10.18.35.10 eth1: 10.18.35.20 > > gw1: 10.18.35.11 gw2: 10.18.35.21 > > | | > > | | > > LAN--------------------10.18.35.0/24----------------- > > | | > > | | > > Apache> WEB1 10.18.35.51:8088 WEB2 10.18.35.52:8088 > > Apache> WEB1 10.18.35.51:8089 WEB2 10.18.35.52:8088 > > > > > > ### LVS ### > > The two LVS servers have a VIP and a GW. > > LVS1 & LVS2 have ip_forward set to 1. > > > > LVS1 has the following iptables: > > iptables -t nat -A PREROUTING -i eth0 -j DNAT --to 192.168.0.111 > > iptables -t nat -A POSTROUTING -o eth0 -j SNAT --to 192.168.0.111 > > with ipvsadm forwarding vip1:8088 to web1:8088 & web2:8088 > > > > LVS2 has the following iptables: > > iptables -t nat -A PREROUTING -i eth0 -j DNAT --to 192.168.0.121 > > iptables -t nat -A POSTROUTING -o eth0 -j SNAT --to 192.168.0.121 > > with ipvsadm forwarding vip1:8089 to web1:8089 & web2:8089 > > > > ### WEB ### > > The two Web servers have 2 virtual web servers listening on ports 8088 & > > 8089 and have the following iptables & iproute2 config: > > iptables -t mangle -A PREROUTING -p tcp --dport 8088 -i eth0 -j MARK > > --set-mark 1 > > iptables -t mangle -A PREROUTING -p tcp --dport 8089 -i eth0 -j MARK > > --set-mark 2 > > > > ip route add table 1 default via 10.18.35.11 dev eth0 > > ip route add table 2 default via 10.18.35.21 dev eth0 > > > > ip rule add fwmark 1 table 1 > > ip rule add fwmark 2 table 2 > > > > WEB1's default GW is set to gw1. > > WEB2's default GW is set to gw2. > > > > CLIENTS should be able to connect to vip1:8088 and vip2:8089 > > > > ### MY PROBLEM ### > > > > If i set WEB2's default GW to gw1, everything works as expected (as I > > now only have one GW). > > But when trying to set WEB2's default GW to gw2, things don't work. > > For example, if i was to run: curl vip1:8088 from a CLIENT, I would be > > able to connect to web1:8088 via LVS OK, but unable to connect to > > web2:8088 should LVS take me to web2. > > > > Its as though the iptables/ip route settings are not working as they > > should. > > > > Any ideas what I'm doing wrong? > > Many thanks, W Agtail. > > Well give I am not sure what you are trying to do, I will take a guess. > I think you are trying to have redundant load balancers and multiple web > servers behind those two load balancers. Here is how I would do it: > > LAN--------------------192.168.0.0/24----------------- <= CLIENTS > | | > | | > LVS1 LVS2 > vrrp: 192.168.0.110 (linked) vrrp: 192.168.0.110 (linked) > eth0: 192.168.0.111 eth0: 192.168.0.112 > > eth1: 10.18.35.11 eth1: 10.18.35.12 > vrrp: 10.18.35.10 (master) vrrp: 10.18.35.10 (slave) > | | > | | > LAN--------------------10.18.35.0/24----------------- > | | > | | > Apache> WEB1 10.18.35.51:8088 WEB2 10.18.35.52:8088 > Apache> WEB1 10.18.35.51:8089 WEB2 10.18.35.52:8088 > > So using VRRP to have a shared virtual IP between the two load > balancers, any client can connect to 192.168.0.110 and be sent through > to one of the web servers. The server side interface also has a VRRP > virtual IP shared between the two load balancers, which is linked to the > other virtual IP, so that if the link goes down on one side of the load > balancer, it will automatically drop the virtual IP on both sides to let > the slave machine take over control of the IP. To the clients this > should be pretty transparent since they don't need to know the IP > changed, other than the momentary change in mac address (letting vrrp > play with the mac address just causes a terrible mess in my experience, > and I have had much better luck by simply changing IPs and letting the > clients relear the new mac). > > keepalived's vrrp works very well (Hmm, actually I think I made some > fixes to it, which I don't remember if I sent back upstream yet. I > should check that tomorrow). > > You could run multiple vrrps per interface if you want to somehow have > one be the master of one IP and the other the master of another to allow > different traffic to use each load balancer by default, but everything > going through one in case of a failure. > > -- > Len Sorensen - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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