NIS / YP make – mail.aliases Callback timed out

on the MASTER nis /etc/ypserv.securenets along with your network definitions put a line similar to :

host  10.10.10.10

where 10.10.10.10 is the IP address of your SLAVE server.

On the SLAVE server (same file) put

host  11.11.11.11

where 11.11.11.11 is the IP of the MASTER server. And that's it :)

Funnily enough, I was doing that just this morning, to verify that people were talking to my new NIS server.

Firstly, find the port that ypserv is on with

oldserver> rpcinfo -p|grep ypserv
    100004    2   udp    844  ypserv
    100004    1   udp    844  ypserv
    100004    2   tcp    847  ypserv
    100004    1   tcp    847  ypserv

Then, you can use tcpdump to look for traffic:

oldserver> sudo tcpdump -n -n port 847 or port 844
[...]
15:09:18.714526 IP 192.168.20.102.707 > 192.168.1.87.844: UDP, length 56
15:09:18.714679 IP 192.168.1.87.844 > 192.168.20.102.707: UDP, length 28
15:09:20.717203 IP 192.168.1.105.900 > 192.168.1.87.844: UDP, length 56
15:09:20.717296 IP 192.168.1.87.844 > 192.168.1.105.900: UDP, length 28
15:09:21.326160 IP 192.168.1.39.719 > 192.168.1.87.844: UDP, length 56
15:09:21.326225 IP 192.168.1.87.844 > 192.168.1.39.719: UDP, length 28

As you can see, my server (192.168.1.87) is definitely getting traffic. If you don't see anything after a half-hour or so, you're not getting anything.