Re: sent an invalid ICMP type 11, code 0 error to a broadcast: 0.0.0.0 on lo?

[Michael Tokarev <mjt@tls.msk.ru>]

Richard B. Johnson wrote:
> On Wed, 6 Jul 2005, Michael Tokarev wrote:
> 
>> kernel: 192.168.4.2 sent an invalid ICMP type 11, code 0 error to a
>> broadcast: 0.0.0.0 on lo
[]
>> All the IP addresses mentioned are local to this box.


[]
> Are you sure `lo` is configured properly, i.e.

Yes.  More, rp_filter is activated on all interfaces.

> ifconfig lo 127.0.0.1 netmask 255.0.0.0
> route add -net 127.0.0.0 netmask 255.0.0.0 dev lo
> 
> There should be no LAN routes going through lo.

There's no.

> It looks as though there are:
> 
>> kernel: 192.168.4.2 sent an invalid ICMP type 11, code 0 error
>> to a broadcast: 0.0.0.0 on lo
> 
>                              |________ 192.168.4.2 pinged lo
> 
> Only the 127.0.0.0 network should be routed through the loop-back
> device.

Again: All the IP addresses mentioned are local to this box.

If you ping an IP address on your eth0, the traffic will "go"
over loopback.  You can verify it using tcpdump:

1: lo: <LOOPBACK,UP> mtu 16436 qdisc noqueue
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
2: eth0: <BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000
    link/ether 00:a0:d2:1d:a7:63 brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.1/24 brd 192.168.1.255 scope global eth0

# tcpdump -npi lo proto ICMP
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on lo, link-type EN10MB (Ethernet), capture size 96 bytes
15:55:13.679234 IP 192.168.1.1 > 192.168.1.1: icmp 64: echo request seq 1
15:55:13.679269 IP 192.168.1.1 > 192.168.1.1: icmp 64: echo reply seq 1

$ ping 192.168.1.1
PING 192.168.1.1 (192.168.1.1) 56(84) bytes of data.
64 bytes from 192.168.1.1: icmp_seq=1 ttl=64 time=0.060 ms
--- 192.168.1.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.060/0.060/0.060/0.000 ms

/mjt
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