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Does Windows traceroute use ICMP or UDP?
On Windows, tracert sends ICMP Echo Request packets, rather than the UDP packets traceroute sends by default. The time-to-live (TTL) value, also known as hop limit, is used in determining the intermediate routers being traversed towards the destination.
What ICMP message does traceroute use?
All versions of traceroute rely on ICMP type 11 (Time exceeded) responses from each hop along the route. If ICMP type 11 responses are being blocked by your firewall, traceroute will not work. These packets are inbound, not outbound.
Can we block traceroute?
1 Answer. There is no “blocking” of traceroute, tracepath, tracert or whatever the tool gets called. These commands work by setting the TTL/hoplimit of the packet to a specific value and then expect the host to send an ICMP unreachable back if the TTL/hoplimit expired (i.e. decremented to zero).
How does traceroute work when ICMP is blocked?
Traceroute works by explicitly setting the TTL field to different values on outbound packets and observing which routers send the ICMP TTL Exceeded errors back for the different TTL values. If all that is blocked is ICMP Echo Request/Reply (“ping”), this does not inherently block traceroute.
Do you use TCP or UDP in traceroute?
Yes. Many versions of traceroute have a flag that let you choose either, or indeed TCP as well. Traceroute does not correspond with application layer entities; thus use of TCP or UDP does not make any sense. ICMP is a “on top of L3” protocol, and that is what is essentialy used by Traceroute.
What happens if I block ICMP on my router?
This means that if you only block outgoing ICMP packets, ping won’t work but traceroute will. But if you block incoming ICMP packets traceroute won’t be able to receive the ICMP responses from the routers in the route and then it won’t work.
Is there a way to block ICMP echo request?
If all that is blocked is ICMP Echo Request/Reply (“ping”), this does not inherently block traceroute. However, one possible implementation for traceroute is to send specifically ICMP Echo Request packets.