MacBook not able to connect to IRC server over Airport I have a MacBook Air connected to an Airport Express and I am trying to connect to an IRC server.

I am able to connect to the IRC server down the street at the cafe.  I am able to connect to the IRC server over LTE when tethered to my phone.  I contacted my ISP and they were able to connect to the IRC server.

Hence, I believe there is some setting with the Airport Express that needs to be adjusted.

Here is output from nmap, traceroute, ping:

$ nmap -sT -p 6697,6667 irc.xxxx.com

Starting Nmap 6.46 ( http://nmap.org ) at 2014-05-14 09:23 PDT
Note: Host seems down. If it is really up, but blocking our ping probes, try -Pn
Nmap done: 1 IP address (0 hosts up) scanned in 3.09 seconds

$ traceroute irc.xxxx.com
traceroute to irc.xxxx.com (64.156.193.80), 64 hops max, 52 byte packets
 1  10.0.1.1 (10.0.1.1)  3.066 ms  1.178 ms  1.119 ms
 2  64-46-0-1.aquarius.gw.novuscom.net (64.46.0.1)  1.421 ms  1.338 ms  1.308 ms
 3  novus-entertainment-10000m-van.demarc.spectrumnet.us (216.243.24.2)  1.354 ms  1.635 ms  1.275 ms
 4  69.90.98.210 (69.90.98.210)  1.236 ms  1.635 ms  1.312 ms
 5  10ge-xe-0-0-0.van-hc21e-dis-1.peer1.net (216.187.115.129)  1.408 ms  2.051 ms  1.374 ms
 6  10ge.xe-0-2-1.sea-coloc-dis-1.peer1.net (216.187.89.186)  4.753 ms  5.010 ms  4.656 ms
 7  10ge.xe-4-0-0.sea-wes7-dis-1.peer1.net (216.187.89.189)  4.766 ms  4.833 ms  4.973 ms
 8  xe-10-0-0.edge1.seattle3.level3.net (4.59.232.1)  5.223 ms  5.053 ms  4.957 ms
 9  ae-31-51.ebr1.seattle1.level3.net (4.69.147.150)  34.778 ms  35.108 ms  35.086 ms
10  ae-7-7.ebr2.sanjose1.level3.net (4.69.132.49)  35.043 ms  34.841 ms  34.659 ms
11  ae-2-2.ebr2.sanjose5.level3.net (4.69.148.141)  34.890 ms  34.928 ms  35.195 ms
12  ae-6-6.ebr2.losangeles1.level3.net (4.69.148.201)  34.953 ms  34.929 ms  34.774 ms
13  ae-82-82.csw3.losangeles1.level3.net (4.69.137.26)  35.948 ms  34.772 ms  35.104 ms
14  ae-71-71.ebr1.losangeles1.level3.net (4.69.137.5)  34.706 ms
ae-81-81.ebr1.losangeles1.level3.net (4.69.137.9)  35.080 ms
ae-91-91.ebr1.losangeles1.level3.net (4.69.137.13)  35.781 ms
15  ae-5-5.car1.sandiego1.level3.net (4.69.133.205)  49.450 ms  35.271 ms  44.764 ms
16  giglinx-inc.car1.sandiego1.level3.net (4.79.33.230)  35.403 ms  35.212 ms  35.657 ms
17  * *^C

$ ping irc.xxxx.com
PING irc.xxxx.com (64.156.xxx.xx): 56 data bytes
Request timeout for icmp_seq 0
Request timeout for icmp_seq 1
Request timeout for icmp_seq 2
When you network the Mac directly into the novuscom device (bypassing the Aiport) are you able to connect to your IRC?

Is the Airport Express acting as a DHCP server?  Is the novuscom device also acting as a DHCP server?  Problem might be the double NAT.

If so does putting the Airport Express into bridge mode fix the problem?

This discussion also looks promising:

Apple's routers do not use UPnP.

They do offer a similar type of feature, which is called NAT-PMP, or NAT Port Mapping Protocol

Open AirPort Utility - Click Manual Setup
Click the Internet icon
Click the NAT tab below the icons
Insure that there is a check mark next to Enable NAT Port Mapping Protocol

Click the Configure Port Mappings button if you need to specify specific ports to use and set them up on the next window that appears