On Thu, Mar 07, 2002 at 12:37:04PM +0500, Andr?s Gri?? Brandt wrote: > Hi: > > Abstract: Linux connected to two different ISP. Outgoing packets seems to peek randomly it's source IP address, without regards to the router choosen. > > Test bed: > 1. Linux Red Hat 7.2 (fw1) with kernel 2.4.7-10, no patches, all netfilter and adv. routing options on. > 2. One "internet" ethernet card that connect to a switch. The switch connect the two routers also. > 3. Linux have two IP: 200.72.44.226 and 200.27.214.226. > 4. ip route list show: > 200.72.44.224/27 dev eth0 scope link > 200.27.214.224/29 dev eth0 proto kernel scope link src 200.27.214.226 > default equalize > nexthop via 200.27.214.225 dev eth0 weight 1 > nexthop via 200.72.44.225 dev eth0 weight 3 > 6. No MASQ, no SNAT, no DNAT for packets locally generated. > 6. Ethercap running in eth0. > 5. Another Linux (ws1) also running ethercap over the wire between router 200.27.214.225 and the switch (via a hub). This machine have address 200.27.214.227. > > What I see, after running ethercap at the same time (and for the same period) on both machines: > 1. Ethercap on fw1 capture ~4.500 packets, on sw1 capture ~1.900 packets. > 2. On sw1 ethercap show me only packets routed thru router 200.27.214.225. I check the destination mac address, and it definitly router 200.27.214.225. > 3. But on sw1, I see outgoing packets having both source IP 200.27.214.226 and 200.72.44.226. > > This is wrong. Packets with source IP 200.72.44.226 must not reach router > 200.27.214.226. AFIK, an outgoing packet must have a source address in the > same subnet that the router being used. Only if you force it to be that way. You told Linux 'I have 2 default nexthops, and I want 25% of connections to go to 200.27.214.225, 75% to 200.72.44.225' and that is what happened, more or less. If you want to be more specific, create policy rules enforcing your subnet preferences. Regards, bert -- http://www.PowerDNS.com Versatile DNS Software & Services http://www.tk the dot in .tk http://lartc.org Linux Advanced Routing & Traffic Control HOWTO
