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Responses from multicast [Resolved]

On one particular box, i cannot get responses to broadcasted messages to ( For example


DHCPREQUEST on wlan0 to

And see even responses from DHCP server on this network


But actual interface is not receiving it. It works on all other interfaces and also on other boxes on the same network. This box has fresh minimal Debian, no firewall.

What can it be?

PS: The problem is not only with DHCP (even if client is not getting ip because of it). But any message sent to and being responded reaches box, but cannot be read from the interface.

Here the output on netstat -g for this interface

wlan0           1
wlan0           1

Update 1: As per request here routing tables of this interface

**me@host:~ $ ip address show dev wlan0**
3: wlan0:  mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether *[MAC]* brd ff:ff:ff:ff:ff:ff
    inet brd scope global wlan0
       valid_lft forever preferred_lft forever
**me@host:~ $ ip route show dev wlan0** proto kernel scope link src
**me@host:~ $ ip route show dev wlan0 table local**
broadcast proto kernel scope link src
local proto kernel scope host src
broadcast proto kernel scope link src

But when remote endpoint replies to zero network multicast (e.g. or I see packets coming and cannot handle it (e.g. netcat -ul 68 not responding)

IP (tos 0x0, ttl 64, id 11512, offset 0, flags [DF], proto UDP (17), length 76) > UDP, length 48
IP (tos 0x0, ttl 64, id 509, offset 0, flags [none], proto UDP (17), length 156) > UDP, length 128

Question Credit: Tamir
Question Reference
Asked October 15, 2017
Posted Under: Unix Linux
1 Answers

Well, the issue is solved. It was actually related to something, which I not quite understand. Basically, in addition to regular route, for some reason, in order to enable reading from unicasting endpoint, i should add default route, source and metrics. So following fully solves the issue for network

ip route add default via src metric 303 dev wlan0
ip route add via src metric 303 dev wlan0

Not sure though, why kernel route is not enough...

credit: Tamir
Answered October 15, 2017
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