Supposing I have several loopback interfaces:
/etc/rc.conf
And then I have an authoritative DNS server (for testing my zone) listening on an address associated with
That server can be access like that:
and it works just fine. What baffles me is that
So my question is: why does tcpdump see those packets on lo0, given that the packets are supposedly transmitted and received on lo1?
lo0
and lo1
. lo0
is configured implicitly by the system, configuration of lo1
follows:/etc/rc.conf
Code:
cloned_interfaces="lo1:sticky"
ifconfig_lo1="inet 192.168.30.1 netmask 255.255.255.0"
ifconfig_lo1_alias0="inet 192.168.30.2/32"
ifconfig_lo1_alias1="inet 192.168.30.3/32"
ifconfig_lo1_alias2="inet 192.168.30.4/32"
And then I have an authoritative DNS server (for testing my zone) listening on an address associated with
lo1
:
Code:
# sockstat | grep ":53"
bind named 1648 15 udp4 192.168.30.3:53 *:*
bind named 1648 16 udp4 192.168.30.3:53 *:*
bind named 1648 17 tcp4 192.168.30.3:53 *:*
bind named 1648 19 tcp4 192.168.30.3:53 *:*
That server can be access like that:
Code:
# dig @192.168.30.3 site-01.example.com
and it works just fine. What baffles me is that
tcpdump
utility can't sniff interaction between dig and named on lo1
, but instead can sniff the packets on lo0
:
Code:
# tcpdump -ni lo1
tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
listening on lo1, link-type NULL (BSD loopback), snapshot length 262144 bytes
^C
0 packets captured
0 packets received by filter
0 packets dropped by kernel
# tcpdump -ni lo0
tcpdump: verbose output suppressed, use -v[v]... for full protocol decode
listening on lo0, link-type NULL (BSD loopback), snapshot length 262144 bytes
01:05:17.318083 IP 192.168.30.3.18286 > 192.168.30.3.53: 16590+ [1au] A? site-01.example.com. (60)
01:05:17.318182 IP 192.168.30.3.53 > 192.168.30.3.18286: 16590*- 1/0/1 A 78.107.232.96 (92)
^C
2 packets captured
2 packets received by filter
0 packets dropped by kernel
So my question is: why does tcpdump see those packets on lo0, given that the packets are supposedly transmitted and received on lo1?