[Linux-cluster] TTL on multicast packets set to 1 by default?

[Steven Dake]

My apologies I must have missed that email.

The code in openais is untested in a routed environment because I dont
have any routed environments to test with.  This is why TTL is not
configurable in the current openais or tested with any values greater
then 1.  I can build you an RPM with ttl set to some greater value to
test with if you like.

Regards
-steve
 
On Wed, 2007-09-19 at 18:15 +1000, Nikolas Lam wrote:
> 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
> 
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