This tclsh script implements the UNIX host command on IOS. The host.tcl script is currently limited to IPv4 A, IPv6 AAAA, and PTR lookups only. It can also dynamically determine the DNS server by looking at the running config. However, if you want to specify a DNS server to use, that is also possible. To use the script, do the following: tclsh host.tcl HOST [DNS SERVER] Where HOST is the hostname or IP address to lookup, and DNS SERVER is an optional DNS server name or IP address. Add a "-6" option to do an IPv6 AAAA lookup.