Netstat for Cisco Routers :-)

With the introduction of Control Plane Policing features (available from 12.3(4)T), you can easily inspect all the open ports (servers and clients) on a router with the show control-plane host open-ports command, resulting in a printout very similar to the netstat -a printout on a Unix/Windows workstation.

For example, on the router where I've configured BGP, HTTP server, NTP and DHCP, this command produces the following output (a session to a BGP neighbor as well as a telnet session was established):

R1#show control-plane host open-ports
Active internet connections (servers and established)
Prot   Local Address  Foreign Address          Service    State
tcp            *:23              *:0           Telnet   LISTEN
tcp            *:80              *:0        HTTP CORE   LISTEN
tcp           *:179              *:0              BGP   LISTEN
tcp           *:179   10.0.7.2:43962              BGP ESTABLIS
tcp            *:23   10.0.7.2:18036           Telnet ESTABLIS
udp            *:67              *:0    DHCPD Receive   LISTEN
udp            *:68              *:0     BootP client   LISTEN
udp           *:123              *:0              NTP   LISTEN

This show command does not display non-TCP/UDP servers
(OSPF, EIGRP, RSVP)or even some UDP-based services (RIP).

Prior to IOS 12.4T You can use both show ip sockets
and show tcp brief.

Best Regards,
Deepak Arora