Original Message:
Sent: 05-04-2021 10:21
From: Unknown User
Subject: How to identify whether the destination is reachable via the next hop ?
Hi Gongyayu,
As Aaron suggested, please provide output for the following:
show route 192.168.0.2
this could be due to a number of things, either ISP is not allowing traffic, remote end does not respond to ICMP or simply discards your packet and so many other possibilities. I'm not aware of a way to verify reachability of destination from your next-hops perspective. however, I have been in this situation before and this is what I did.
Typically your ISP facing interface has a public ip that is part of your ISP's ASN, meaning its most probably aggregated part of a larger /24 at minimum or even larger prefixes. you can source your traceroute/ ping from that ip, this will test reachability of the remote site from the /30 IP space owned by ISP (lets assume thats what you get from your ISP) and will not account for anything internal to you (the subscriber/ end user).
run traceroute 192.168.0.2 no-resolve source <ISP facing public-ip>
Original Message:
Sent: 05-01-2021 19:43
From: Unknown User
Subject: How to identify whether the destination is reachable via the next hop ?
Assume the next hop is ISP and I receive very limited information, say only the peering IP. How can I identify the destination is reachable via that ISP?
I did the following and sometimes I got destination unreachable message.
root@Branch1# run traceroute 192.168.0.2 no-resolvetraceroute to 192.168.0.2 (192.168.0.2), 30 hops max, 40 byte packets 1 172.16.1.6 5.590 ms !N 2.315 ms !N 1.855 ms !Nroot@Branch1# run ping 192.168.0.2PING 192.168.0.2 (192.168.0.2): 56 data bytes36 bytes from 172.16.1.6: Destination Net UnreachableVr HL TOS Len ID Flg off TTL Pro cks Src Dst 4 5 00 0054 716b 0 0000 40 01 9b7e 172.16.1.5 192.168.0.2
But this might be turned off by ISP. Any other way can I get the similar message. So I can conclude the destination is not reachable via the ISP.
thanks in advance !!