27 reputation
6
bio website lmframework.com
location Milan, Italy
age
visits member for 4 years, 5 months
seen Oct 30 at 15:38

May
15
answered Network packets flowing both ways but still can't communicate
May
15
accepted Rackspace - if I delete a server will I lose the backups?
May
15
awarded  Supporter
May
15
revised Packets returning but traceroute fails
edited body
May
15
comment Packets returning but traceroute fails
ABSOLUTELY AMAZING - IT WORKS!! I've been bashing my head on this problem all week and just today spent 12 hours on it. God bless you @kaspered you are brilliant!
May
15
accepted Packets returning but traceroute fails
May
15
comment Packets returning but traceroute fails
BTW, traffic from eth1's own subnet can get through OK.
May
15
awarded  Commentator
May
15
comment Packets returning but traceroute fails
Same thing happens. Wireshark sees the probes coming in but they are not replied to. It is as if all incoming traffic on eth1 is dropped even though the firewall is disabled and iptables is empty.
May
15
comment Packets returning but traceroute fails
Nope - exactly the same issue. Wireshark sees the echo replies but they don't make it back to the ping command.
May
15
comment Packets returning but traceroute fails
That's a fantastic answer! I tried setting rp_filter to 0 for eth1 but nothing changed. I don't think I've got an asymmetric routing problem because all the hosts on all the subnets have the same L3 switch as their default gateway. In fact, the topology for eth0 is identical to eth1. At the moment the default route is via eth0, but if I change it to eth1 then all the above works but the problem just moves to eth0. I'm convinced it has something to do with eth1 not being the 'default' NIC. BTW, /proc/sys/net/ipv4/ip_forward is intentionally zero.
May
15
revised Packets returning but traceroute fails
added 19 characters in body
May
15
asked Packets returning but traceroute fails
May
15
comment Network packets flowing both ways but still can't communicate
@DennisNolte After disabling eth0, the traceroute command gave the same results. This is not a surprise because even with eth0 enabled the first hop is the switch interface at 192.168.12.1 which is correct for eth1.
May
15
comment Network packets flowing both ways but still can't communicate
@DennisNolte I see what you mean but I don't think it's a problem with multiple routes. By forcing traceroute to use eth1 on the linux box there is only one possible route to choose. The box on the 192.168.1.0 network only has one NIC and so has only one default route (which is the address of the switch).
May
15
comment Network packets flowing both ways but still can't communicate
@Jeroen The the three routes are set up on the switch as VLANS hence the routing table is generated automatically. The switch's routing table is basically that shown in my question.
May
15
asked Network packets flowing both ways but still can't communicate
Aug
5
comment Is my vision of the ideal CDN wrong?
Thanks gekkz, I started to notice that after reading more on the topic
Aug
5
comment Is my vision of the ideal CDN wrong?
Thanks Joris, very kind. I don't have enough reputation (yet) to vote you up..
Aug
5
awarded  Scholar