On Fri, 2007-08-24 at 09:17 -0700, Steven Dake wrote: > If you are having problems with the default multicast address > 239.192.x.x it is probably because your switch is not sending those > packets because of a configuration issue. > > If you have this problem please contact me. I would like to make a > cookbook of switch manufacturer/models and possible solutions. > > Using 224.0.0.x is not recommended as these multicast packets are > broadcoast over the network. > > Regards > -steve Hi Steve, I'm not sure if the problems I'm having are caused by switch configuration or compatibility - would the following be a good way to determine if the multicast communications are working? 1) Check what multicast group (IP) the nodes have chosen using netstat -gn ? e.g. for host0, I'm guessing that cman is using 239.192.205.2 (as I think 225.0.0.12 is for the fence_xvmd Xen virtualised host group and I can't see any activity on 224.0.0.251). [root@host0 ~]# netstat -g IPv6/IPv4 Group Memberships Interface RefCnt Group --------------- ------ --------------------- lo 1 all-systems.mcast.net eth0 1 224.0.0.251 eth0 1 225.0.0.12 eth0 1 239.192.205.2 eth0 1 all-systems.mcast.net [root@host0 ~]# 2) Use tcpdump to check that this node is receiving transmissions from *other* nodes to the multicast group. e.g. [root@host0 ~]# tcpdump -i any -nn host 239.192.205.2 and ip multicast tcpdump: WARNING: Promiscuous mode not supported on the "any" device tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on any, link-type LINUX_SLL (Linux cooked), capture size 96 bytes 13:42:03.674676 IP 172.31.99.50.5149 > 239.192.205.2.5405: UDP, length 118 13:42:03.767820 IP 172.31.99.50.5149 > 239.192.205.2.5405: UDP, length 74 13:42:03.962382 IP 172.31.99.50.5149 > 239.192.205.2.5405: UDP, length 74 13:42:04.162652 IP 172.31.99.50.5149 > 239.192.205.2.5405: UDP, length 118 13:42:04.267768 IP 172.31.99.50.5149 > 239.192.205.2.5405: UDP, length 74 13:42:04.450195 IP 172.31.99.50.5149 > 239.192.205.2.5405: UDP, length 74 13:42:04.650646 IP 172.31.99.50.5149 > 239.192.205.2.5405: UDP, length 118 13:42:04.766404 IP 172.31.99.50.5149 > 239.192.205.2.5405: UDP, length 74 13:42:04.940367 IP 172.31.99.50.5149 > 239.192.205.2.5405: UDP, length 74 9 packets captured 19 packets received by filter 0 packets dropped by kernel [root@host0 ~]# In the above example I can only see transmissions to 239.192.205.2 from 172.31.99.50 (hosts0's IP address). If things were working properly, I'd be able to see transmissions from other source addresses wouldn't I? E.g. I should have at least some entries like this 13:42:04.940367 IP 172.31.99.100.5149 > 239.192.205.2.5405: UDP, length 74 where the source address is a different node, right? Regards, Nik Lam -- Linux-cluster mailing list Linux-cluster@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/linux-cluster
