Some weeks ago I posted to this list reporting problems with my 2-node RHEL5 cluster where I had each node on a different VLAN, connected by a layer 3 router. The problem was that the OpenAIS (cluster communications) packets were not reaching the other node, so all sorts of annoying things were happening. Well, I've just had someone with extensive multicast experience help me with some troubleshooting. We've discovered that the problem appears to be that the packets are going out with a TTL of 1, which means the first router to receive it will drop it without forwarding. Here's a piece of tcpdump -v 04:47:23.167506 IP (tos 0x0, ttl 1, id 0, offset 0, flags [DF], proto UDP (17), length 102) 172.16.99.50.5149 > 239.224.72.11.5405: UDP, length 74 04:47:23.336194 IP (tos 0x0, ttl 1, id 0, offset 0, flags [DF], proto UDP (17), length 102) 172.16.99.50.5149 > 239.224.72.11.5405: UDP, length 74 04:47:23.538871 IP (tos 0x0, ttl 1, id 0, offset 0, flags [DF], proto UDP (17), length 146) 172.16.99.50.5149 > 239.224.72.11.5405: UDP, length 118 04:47:23.658161 IP (tos 0x0, ttl 1, id 0, offset 0, flags [DF], proto UDP (17), length 102) 172.16.99.50.5149 > 239.224.72.11.5405: UDP, length 74 04:47:23.826268 IP (tos 0x0, ttl 1, id 0, offset 0, flags [DF], proto UDP (17), length 102) 172.16.99.50.5149 > 239.224.72.11.5405: UDP, length 74 04:47:24.026863 IP (tos 0x0, ttl 1, id 0, offset 0, flags [DF], proto UDP (17), length 146) 172.16.99.50.5149 > 239.224.72.11.5405: UDP, length 118 So, I guess the question is, what is the correct method to set the TTL to be a bit more reasonable, say 128? Regards, Nik Lam -- Linux-cluster mailing list Linux-cluster@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cluster
