[Dnsmasq-discuss] No more random source port

Risto Suominen risto.suominen at gmail.com
Tue Mar 21 06:48:56 GMT 2017


Hi Albert,

2017-03-21 0:03 UTC+02.00, Albert ARIBAUD <albert.aribaud at free.fr>:
>
> Source IP is not the same in both pcaps. 1st pcap queries 8.8.8.8 and
> 192.168.1.1 from 192.168.1.33, while 2nd pcap queries are from
> 192.168.1.100. Can you clarify your network setup?
>
IP is differerent, but MAC is the same. I'm currently using Zyxel
router (pcap 1), because it's working. With TP-Link router (pcap 2) I
don't reach the Internet, because of the DNS problem.

So, I simply plugged my computer to different routers. In both cases
the router's DHCP server gave me IP and DNS addresses, Zyxel:
192.168.1.33 and 8.8.8.8 (its own address is 192.168.1.1). TP-Link:
192.168.1.100 and 192.168.1.1 (its own address).

Possibly the problem with TP-Link depends on this behaviour
(forwarding DNS requests). (NAT routers typically allocate random
ports internally for forwarded requests.)

I might change Zyxel's setup so that it gives me its own address as
DNS, to see how it behaves in that situation. In TP-Link I have not
found a way to do the opposite.

Risto



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