For security purposes we “firewall” off UDP ping (traceroute) responses from certain pieces of our core networking equipment. As such, traceroutes into your server from certain networks may show unexpected results.
For example, the following traceroute shows a successful trace into Superb’s network from the University of Maryland (umd.edu):
1 Vlan5.css-nts-r1.net.umd.edu (128.8.5.60) 0.539 ms 0.520 ms 0.610 ms
2 Gi5-1.css-core-r1.net.umd.edu (128.8.0.9) 0.618 ms 0.613 ms 1.266 ms
3 Gi3-2.css-fw-r1.net.umd.edu (128.8.0.82) 1.413 ms 1.344 ms 1.112 ms
4 Gi2-1.css-max-r1.net.umd.edu (128.8.0.234) 0.929 ms 1.163 ms 1.443 ms
5 clpk-umd-isp.maxgigapop.net (206.196.177.154) 0.891 ms 1.232 ms 0.970 ms
6 65.120.78.45 (65.120.78.45) 1.565 ms 1.698 ms 1.595 ms
7 * * *
8 * * *
9 slsdemo.dca2.superb.net (66.36.230.20) 2.625 ms 2.610 ms 2.550 ms
In this example hops numbered #7 and #8 are core pieces of Superb’s network and as such their responses have been “firewalled” and are not visible.
Please note that if your server has a firewall which blocks UDP pings (used by traceroute to determine paths), the above example would be missing hop #9 as well. When the traceroute utility cannot determine if its destination host has been reached it will continue scanning until hop #30, which may produce strange and misleading results.
