Why does traceroute only sometimes fail to ping my ISP?

Question

I've read that it's fairly common for the first hop or two of a traceroute to only return timed out, as the ISP servers refuse all pings; what does it mean if only some of those pings are dropped/refused? Specifically, here's what I mean:

    Tracing route to superuser.com [151.101.1.69]
over a maximum of 30 hops:

  1    <1 ms    <1 ms    <1 ms  192.168.0.1
  2     *        *       14 ms  cblmdm170-253-252-1.maxxsouthbb.net [170.253.252.1]
  3    11 ms    10 ms    12 ms  core-sw5-stk-xe-1-0-5.maxxsouthbb.net [24.213.111.77]
  4     8 ms    11 ms    10 ms  core-mx1-stk-ae1.maxxsouthbb.net [24.245.114.1]
  5    28 ms    29 ms    27 ms  h97.231.134.40.static.ip.windstream.net [40.134.231.97]
  6    33 ms    29 ms    29 ms  et3-0-0-0.cr01.dlls01-tx.us.windstream.net [40.134.225.108]
  7    32 ms    30 ms    30 ms  ae-21.r01.dllstx04.us.bb.gin.ntt.net [129.250.203.17]
  8    30 ms    31 ms    29 ms  ae-0.fastly.dllstx04.us.bb.gin.ntt.net [130.94.195.58]
  9    34 ms    32 ms    26 ms  151.101.1.69

Tracing route to superuser.com [151.101.1.69]
over a maximum of 30 hops:

  1    <1 ms    <1 ms    <1 ms  192.168.0.1
  2     *       13 ms     9 ms  cblmdm170-253-252-1.maxxsouthbb.net [170.253.252.1]
  3    11 ms    11 ms    12 ms  core-sw5-stk-xe-1-0-5.maxxsouthbb.net [24.213.111.77]
  4    11 ms    10 ms    11 ms  core-mx1-stk-ae1.maxxsouthbb.net [24.245.114.1]
  5    31 ms    33 ms    31 ms  h97.231.134.40.static.ip.windstream.net [40.134.231.97]
  6    31 ms    31 ms    32 ms  et3-0-0-0.cr01.dlls01-tx.us.windstream.net [40.134.225.108]
  7    31 ms    32 ms    31 ms  ae-21.r01.dllstx04.us.bb.gin.ntt.net [129.250.203.17]
  8    27 ms    30 ms    31 ms  ae-1.fastly.dllstx04.us.bb.gin.ntt.net [130.94.195.62]
  9    31 ms    28 ms    28 ms  151.101.1.69

Anywhere between none of the three or all of the three pings make it back -- it seems to be pretty random.

I'm connected to the internet through wired directly through my modem in an apartment complex. I noticed that the second hop that's dropping these pings has the hostname "cblmdm" and has an IP similar to my external IP -- is that my modem, or is it probably just a switch/modem elsewhere in the apartment building?

Is it just a result of the way that their server's set up? Problems with my modem? Packet loss? Sorry, I'm new to interpreting traceroutes -- mostly, I'm concerned with whether it's benign or symptomatic of other issues with the network, as I have experienced packet loss issues on this network for quite a while. Thanks!

Answer 1

ICMP packets (such as ping's echo request and echo reply) have a lower priority than TCP and UDP. Generally, if a router is overloaded, it will drop ICMP packets so it can process more TCP and UDP packets.

This is just a general observation and may not be what's happening in this specific instance.

If all packets were being dropped consistently the. One could assume that the router's configured to always drop ICMP.