This is a followup to this question I saw on SuperUser, to which no answer has been provided.
A user deleted the second route in his routing table,
# ip route show
default via 192.168.73.1 dev eth0 proto static
192.168.73.0/24 dev eth0 scope link
leaving only his default. He found out he could ping
other pcs on the network, but they could not ping
back the pc with the incomplete routing table.
I investigated this on a real network (as opposed to the original, virtual setting) by means of tcpdump
: it turns out that the incomplete pc does send back a reply to the ping, but this does not reach the originating, wholesome pc.
So I tried opening an ssh session, on both directions, and now both attempts fail. This is Wireshark's capture of the failed connection:
The presence of the PUSH (PSH/ACK) and the large number of retransmissions make it clear either pc is unable to reach the other one.
Can anyone explain why, in some detail?