Re: Need help with ping (DUP!) + route + wlan + more.

• Previous message: Tasos Kotaras: "problem with NFS timeout options"
• In reply to: Alexander Harsch: "Re: Need help with ping (DUP!) + route + wlan + more."
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Date: Tue, 07 Jun 2005 12:21:26 +0200

Hi Alexander =)

Alexander Harsch wrote:

> the DUP means duplicated echo replys. And this is propably the problem. I
> guess, that the server will answer using the ethernet connection, if if you
> contact it using wlan. You might want to try this using tcpdump.

Luckily I have an extra serial console connection to the server, so I can tcpdump
on both network interfaces without making noise on the device myself.

I've run tcpdump both on the server's wlan0 and eth0, and on the client's wlan0 and eth0
in all combinations. And I see nothing wrong: When I wget http://10.0.0.1/index.html from
the client, I only get traffic on the wlan0 devices.

I ran tcpdump while pinging:

When I ping 10.0.0.1 from the client, I only get traffic on wlan0 on both machines.
This is what the client's ping looks like:
        64 bytes from 10.0.0.1: icmp_seq=7 ttl=64 time=1.97 ms
        64 bytes from 10.0.0.1: icmp_seq=7 ttl=64 time=6.22 ms (DUP!)
        64 bytes from 10.0.0.1: icmp_seq=7 ttl=64 time=8.10 ms (DUP!)
        64 bytes from 10.0.0.1: icmp_seq=7 ttl=64 time=10.9 ms (DUP!)

This is the client's tcpdump of wlan0 generated by one ping request towards the server:
        11:48:20.069654 IP 10.0.0.44 > 10.0.0.1: icmp 64: echo request seq 7
        11:48:20.071598 IP 10.0.0.1 > 10.0.0.44: icmp 64: echo reply seq 7
        11:48:20.075844 IP 10.0.0.1 > 10.0.0.44: icmp 64: echo reply seq 7
        11:48:20.077721 IP 10.0.0.1 > 10.0.0.44: icmp 64: echo reply seq 7
        11:48:20.080592 IP 10.0.0.1 > 10.0.0.44: icmp 64: echo reply seq 7

This is the server's tcpdump of wlan0 generated by one ping request from the client:
        21:10:10.146198 IP 10.0.0.44 > 10.0.0.1: icmp 64: echo request seq 7
        21:10:10.146442 IP 10.0.0.1 > 10.0.0.44: icmp 64: echo reply seq 7
        21:10:10.150257 IP 10.0.0.44 > 10.0.0.1: icmp 64: echo request seq 7
        21:10:10.150562 IP 10.0.0.1 > 10.0.0.44: icmp 64: echo reply seq 7
        21:10:10.152332 IP 10.0.0.44 > 10.0.0.1: icmp 64: echo request seq 7
        21:10:10.152637 IP 10.0.0.1 > 10.0.0.44: icmp 64: echo reply seq 7
        21:10:10.155231 IP 10.0.0.44 > 10.0.0.1: icmp 64: echo request seq 7
        21:10:10.155505 IP 10.0.0.1 > 10.0.0.44: icmp 64: echo reply seq 7

When I ping 192.168.17.1 from the client, I only get traffic on eth0 on both machines,
and the ping look good without DUPs. So far so good; traffic streaming through the
proper channels and the "expected" DUPs.

The same goes the other way around, when ping the client from the server:
DUPs on wlan0 and only traffic on either wlan0 or eth0 on both sides.

Under some (unreproducable I think) circumstances, I can get rid of the DUPs.
But still wget://10.0.0.1/index.html from the client just hangs.

> What the
> reason is for this behaviour I can not tell. Maybe you want to take a look
> at the hosts file and and add the wlan ip address of the client.

This is my server's /etc/hosts:
        127.0.0.1 localhost
        192.168.17.1 au1901000039-eth0 au1901000039
        10.0.0.1 au1901000039-wlan0
        10.0.0.44 speedball-wlan0
        10.0.0.44 10.0.0.44
        192.168.17.2 speedball-eth0
        192.168.4.44 speedball-ath0 speedball

The 10.0.0.44=10.0.0.44 was just a desperate attempt; makes no difference.
My server's /etc/resolv.conf is currently empty. I don't know what to put in it,
since the server is on network and makes no use of a DNS currently.

I hope you can help me get further =)
Thank,

-- 
Stephan Henningsen

• Previous message: Tasos Kotaras: "problem with NFS timeout options"
• In reply to: Alexander Harsch: "Re: Need help with ping (DUP!) + route + wlan + more."
• Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]