North American Network Operators Group|
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Re: Refusing Pings on Core Routers??? A new trend?
template response -- I hear is "Well, you can't rely on traceroute because of ICMP prioritisation". When you start to explain how traceroute actually works (both ICMP-based and UDP-based (which still relies on ICMP responses, of course!)), and that ICMP prio should only affect the IP of which the router listens on (and not hops beyond or at the dest), most NOCs fire back with another
If I recall well, Cisco GSRs impose low priority and/or limits for all ICMP traffic flowing thru the box, not just packets to/from router itself, and there's not a knob to adjust that. Also of notice is that packets that expire TTL needs some kind of low-path processing, and will be subject to increased latency or loss compared to normal ones, and this affects every tool to trace packets thru the network I've seen.