* * * in traceroute

Question

If I traceroute to my server via a bunch of different methods, the external ip seems to not work. However the server is online and accessible by this ip.

Localhost:

michaelxu@michaelxu-server:~$ traceroute 127.0.0.1
traceroute to 127.0.0.1 (127.0.0.1), 30 hops max, 60 byte packets
 1  localhost.localdomain (127.0.0.1)  0.120 ms  0.069 ms  0.064 ms

Internal Ip:

michaelxu@michaelxu-server:~$ traceroute 192.168.1.3
traceroute to 192.168.1.3 (192.168.1.3), 30 hops max, 60 byte packets
 1  michaelxu-server (192.168.1.3)  0.122 ms  0.065 ms  0.067 ms

External IP:

michaelxu@michaelxu-server:~$ traceroute 24.24.174.153
traceroute to 24.24.174.153 (24.24.174.153), 30 hops max, 60 byte packets
 1  * * *
 2  * * *
 3  * * *
 4  * * *
 5  * * *
 6  * * *
 7  * * *
 8  * * *
 9  * * *
10  * * *
11  * *^C
michaelxu@michaelxu-server:~$

...it contines all the way to 30 ... the same thing happens if I traceroute it through the dns server

It also occurs if i do it from another online service:

   Tracing route to cpe-24-24-174-153.socal.res.rr.com [24.24.174.153]...

hop rtt rtt rtt     ip address  fully qualified domain name
1   1   1   1       70.84.211.97    61.d3.5446.static.theplanet.com
2   0   0   0       70.87.254.5 po101.dsr02.dllstx5.networklayer.com
3   0   0   1       70.85.127.109   po52.dsr02.dllstx3.networklayer.com
4   0   0   0       173.192.18.230  ae17.bbr02.eq01.dal03.networklayer.com
5   0   0   0       66.109.9.97 ae-11-0.pr0.dfw10.tbone.rr.com
6   41  40  39      66.109.6.208    ae-6-0.cr0.dfw10.tbone.rr.com
7   39  39  40      66.109.6.0  ae-3-0.cr0.lax30.tbone.rr.com
8   37  39  39      66.109.6.65 
9   42  40  39      72.129.9.3  agg1.lamrcadq-ccr02.socal.rr.com
10  36  36  35      72.129.10.73    
11  53  60  49      24.24.209.18    ge17-0-spsdca1-ars1.socal.rr.com
12  *   *   *           
13  *   *   *           
14  *   *   *           
15  *   *   *       

What do the * * * mean? Is there any way to "fix this"

Answer 1

There's two reasons for it.

1) A timeout. Although usually you'll eventually get replies in one of the rtt positions like 70 * * or something.

2) Some routers are configured to block some parts of the ICMP protocol from working (ICMP echo to be precise). This is usually to help prevent DDOS attacks etc. Traceroute depends on ICMP echo working.

Essentially, the traceroute tool can't work out the IP address so you'll get * * * for hosts that are blocked. Eventually you may get a response from other hosts so you may see responses at larger hop counts.

See the wikipedia article on traceroute. In your case, it's cause number 2 and there isn't anything you can do about it. Try running traceroute to another destination and you may get a full trace.