How do you know if it's a loop?

Question

Computer networks

There is a suspicion that there is a loop in the network.
Everything seems to be working, but when pinging the gateway it gives out:
Превышен срок жизни (TTL) при передаче пакета.
When using tracert, it jumps back and forth 30 times to the gateway, TMG is installed on IS

1    <1 мс    <1 мс    <1 мс  192.168.1.1
 2    <1 мс     *       <1 мс  is.compeng.ru [192.168.1.16]
 3    <1 мс    <1 мс    <1 мс  192.168.1.1
 4    <1 мс     *       <1 мс  is.compeng.ru [192.168.1.16]
 5     3 ms    <1 мс    <1 мс  192.168.1.1
 6    <1 мс     *       <1 мс  is.compeng.ru [192.168.1.16]
 7    <1 мс     1 ms    <1 мс  192.168.1.1
 8    <1 мс     *       <1 мс  is.compeng.ru [192.168.1.16]
 9     1 ms     1 ms     2 ms  192.168.1.1
10     1 ms     *       <1 мс  is.compeng.ru [192.168.1.16]

Looking at this, it begins that somewhere there is a loop.

Answer 1

The loop is not in the network, but in the routing.

Answer 2

Well yes, a routing loop (if mpls is not present). It is logical to check the routing table for is.compeng up to the place where traceroute is launched

Answer 3

Go to the server with TMG and do route print compare it with the local output of a similar command, most likely you have two hosts on the network looking at each other by some route.