[cs615asa] Traceroute shows * * * at the tail

[Xiakun Lu]

> I find in some case,  tracerouting in command prompt will output several * * * lines at the tail, I guess that is because the firewall blocks the ICMP return packets. But when I traceroute it in virsual trace route, it can be reached. 
> Is it because they use different trace route path? Some routers block the ICMP packets, while some not?
> 


Yes, the route path is dynamic due to the router protocol. Even the each line in the outputs can not be guaranteed to use the same path. For example, the first request, whose TTL is 1, may arrive at router A. However, the second request may go through router B to get to router C. Some routers may block different type of ICMP, resulting in different outputs.

Best Regards,

Xiakun Lu
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