R: Help on alert ping

[Andreas Ericsson]

Marco Borsani wrote:
> I am testing check_icmp, but for many hosts (where normally I use
> check_ping) a receive a notification like following:
> 
> "CRITICAL - 10.0.0.1: Time to live exceeded in transit @ 10.0.0.255. rta
> nan, lost 100%"
> 
> Any idea?
> 

You can try using the -l flag to set ttl to a higher value on outgoing 
packets. The ttl decides the max number of hops/seconds a packet is 
allowed to live. The value reached first results in a ttl exceeded. "in 
transit" means the target host is more than outgoing_ttl hops away. "in 
packet reassembly" means fragments of the packet didn't arrive a maximum 
of remaining_ttl seconds after the IP-header on some router along the 
way. I've never seen the "in packet reassembly" happen on a modern 
network (not without making it, anyway).

Also, check_icmp doesn't auto-increment it's ttl as normal ping may or 
may not do (system dependent). This is intentional, since it means it 
can be used to monitor the number of hops to a host and thus see if the 
normal or failover route is being used.

-- 
Andreas Ericsson                   andreas.ericsson at op5.se
OP5 AB                             www.op5.se
Lead Developer


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