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Will traceroute work if ICMP is blocked?
traceroute relies on both UDP and ICMP to work effectively. If you block the ICMP messages that are in response to traceroute then the traceroute-ing host will time out. Every time the UDP packet reaches these hops, the hops would send a TTL number of hops exceeded message.
Does traceroute require ICMP?
The traceroute command uses ICMP Time Exceeded messages to trace a network route.
Does traceroute send ICMP?
A traceroute works by sending Internet Control Message Protocol (ICMP) packets, and every router involved in transferring the data gets these packets.
Does UDP use ICMP?
How does ICMP work? Unlike the Internet Protocol (IP), ICMP is not associated with a transport layer protocol such as TCP or UDP. This makes ICMP a connectionless protocol: one device does not need to open a connection with another device before sending an ICMP message.
Which ICMP message confirms the traceroute is completed?
Traceroute is a simple ICMP Echo/Echo Reply packet with its Time To Live (or Time to Life) field (TTL) increased by one, for every ping reply (echo reply) it receives. For example, when you traceroute to a specific IP address, an ICMP echo is sent with a TTL =1.
How does Cisco traceroute work for ICMP no reply?
Traceroute of Cisco uses UDP packets (TX) with increment in PORT number for EACH packet (it won’t be constant at 33434, try “debug ip udp” while tracing) starting from 33434 and increasing TTL value by default and trace the path using ICMP Time exceeded messages from in between hops and ICMP port unreachable message from the final destination.
Why do I get no response to my ICMP ping?
If your gateway doesn’t have proxy ARP enabled, you will get no response to the ARP and your ping will fail. A PC that has the gateway’s IP address configured will succeed with the ping (if no other issues exist of course). So, as a first step, try to configure the static route with a next-hop IP address.
Why does traceroute # 9 stop at Min?
In the configuration below, ICMP is blocked at MIN’s FastEthernet0/0 interface; afterwards a traceroute is performed (see traceroute #9). Traceroute #9 stops at MIN and MIN reports back a destination net (network) unreachable message due to the ACL applied.
What does ” unreachable host ” mean in ICMP?
* means that your machine received no response. !H means that your machine received ICMP message “destination host unreachable” from the host indicated in the traceroute output. Rarely traceroute can indicate also other unreachable messages like !N or !P (network or protocol) etc.