Multiple HTTP entries in show command

[njccnp]

When entering the command "show control-plane host open-ports" on a router, with web services running and no current connections, the command output shows two entries for Port 80, and two entries for Port 443. Why two of each? Does this mean the router is running multiple processes? Does this dictate how many client connections can be established?

[monika_kispal]

Hi. Does it not say the port types? UDP and TCP?

[njccnp]

They all say tcp. 

[pieterh]

does the router have multiple IP-adresses ? (probably as it is a router) -> an open port per address?

[Joseph W. Doherty]

As a wild guess, starting (?) with HTTP v1.1, an individual client might use concurrent TCP sessions to speed up interaction with the HTTP server.  Possibly it's for that.  (BTW, I also recall [?], HTTP clients [browsers] that used this capability were to limit themselves to a maximum of two concurrent sessions.)

[pieterh]

I found this document about control-plan protection / port-filter
https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos_plcshp/configuration/12-4t/qos-plcshp-12-4t-book/qos-plcshp-cpp.html 

which contains this section:
The port-filter maintains a global database of all open TCP and UDP ports on the router, including random ephemeral ports created by applications. The port database is dynamically populated with entries provided by the registered applications as they start listening on their advertised ports either by configuration of an application (that is SNMP) or initiation of an application (that is, TFTP transfer). An MQC class-map using the list of open ports can be configured and a simple drop policy can be applied to drop all packets destined to closed or nonlistened ports. Port-filter class-maps also support direct match of any user configured TCP/UDP port numbers.

[monika_kispal]

Does this dictate how many client connections can be established?

No. That should be dictated by ip http max-connections. The default is 5. 

I have just succeeded in creating the same output on a totally clear router, I mean I only issued the ip http server command and, I also have double listening ports. I connected to the server, but it lists as an established connection, so the double entry may have nothing to do about your live connections.

Maybe some IPv4 and IPv6 matter? Looking to learn