go
ns1.eschelontelecom.com has one IP number , but the reverse is dnscache1.msp.eschelon.com. dnscache1.msp.eschelon.com point to the same IP. eschelontelecom.com use this as a nameserver. eschelontelecom.com is delegated to two nameservers, however one delegated nameserver is missing in the zone. They are on different IP networks. ns1.eschelontelecom.com is hosted on a server in United States.

ns1.eschelontelecom.com
a records
 
+ 209.150.200.10 209.150.192.0/19 AS7385 dnscache1.msp.eschelon.com
+ --- dnscache1.msp.eschelon.com

eschelontelecom.com
ns-soa records
 
+   AS?  
+ ---  
ns records
ns1.cisco.com
+ 128.107.241.185 128.107.0.0/16 AS109 -
+ --- -
ns1.eschelontelecom.com
+ 209.150.200.10 209.150.192.0/19 AS7385 dnscache1.msp.eschelon.com
+ --- dnscache1.msp.eschelon.com
ip numbers of host
209.150.200.10
ptrs of ip numbers
dnscache1.msp.eschelon.com
hostnames sharing ip with a-records
dnscache1.msp.eschelon.com
domains using this as nameserver
eschelontelecom.com
nameservers missing in zone
ns1.cisco.com