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Old 08-16-2012, 12:19 PM   #1
gobo7
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server 12.04 not excepting connections, not responding to arp requests


brought up ubuntu server 12.04 x64 for the first time to test as an appliance. the nic is a usb wireless adapter (ar9271 chip.) the wireless adapter is configured and authenticates with the ap. the firewall has been disabled (ufw disable).

however, external connections time out. the arp table on the server is not being populated. also, the server is not responding to arp requests. if the arp table is manually populated, connections are possible and the server responds to arp requests from the populated mac.

this is not seen on the wired port. at first, i thought this might be an issue with the the ar9271 adapter. tested it on a slackware 13.37 box and the issue was not witnessed.

does anyone have any suggestions?
 
Old 08-20-2012, 10:12 PM   #2
Ygrex
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what is the issue?
1. the server ignores/declines arp replies
2. the server does not send any arp requests
3. the server send requests but replies do not reach it for some reason
4. the server responds to all arp requests but these are ignored by other devices
... you choice
 
Old 08-20-2012, 11:23 PM   #3
gobo7
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Quote:
Originally Posted by Ygrex View Post
what is the issue?
1. the server ignores/declines arp replies
2. the server does not send any arp requests
3. the server send requests but replies do not reach it for some reason
4. the server responds to all arp requests but these are ignored by other devices
... you choice
none of the above. the server does not reply/respond to initial inbound arp requests.

if you ping or arping the ubuntu server from another device, the server never responds. a tcpdump shows no traffic from the server. the mac of the "pinging device" is not in the arp table.

however, if you manually add the mac of the other device to the ubuntu server's table, the ping from the other device will succeed. alternately, if you ping the other device from the ubuntu server first, the remote device's mac appears in the arp table and the remote ping will complete.

when the server is cold booted, the wireless interface comes up and authenticates (wpa2) on the AP. the ap can ping the server and vice-versa. other than that, the server is deaf to any other devices. i have about come to the conclusion the problem is with the ubuntu supplied ar9271 kernel module.
 
Old 08-20-2012, 11:54 PM   #4
Ygrex
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can you see any arp requests with tcpdump at ubuntu server?
 
Old 08-21-2012, 01:05 AM   #5
gobo7
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Quote:
Originally Posted by Ygrex View Post
can you see any arp requests with tcpdump at ubuntu server?
i want to say no. i'm almost certain i ran tcpdump on the server, but i did this several weeks ago. i suspected the wireless adapter, so i took time out to load slackware 13.37 on the server and test with it. no issues.

at one point i thought the ubuntu firewall might be playing a part, but arp is layer 2 and the firewall is layer 3. well... i assume the firewall is layer 3, i don't know how ubuntu does their firewall. this is my first time to use ubuntu server.
 
Old 08-21-2012, 11:52 AM   #6
Ygrex
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there's no reason to suspect firewall if you cannot see arps with tcpdump, it just doesn't receive them; i've no idea actually
 
Old 08-27-2012, 05:46 PM   #7
Jamie Royer
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I'm experiencing the same issue. Over the weekend I installed FreeSWITCH on the Ubuntu 12.04 Server and configured a SIP phone to register with the server. The phone sends out ARP requests and they are visible on the server but no reply is sent.

The server is a Shuttle PC with an on-board NIC.

The desktop is running Ubuntu 12.04. The phone is a Linksys SPA901.

* I'm able to ssh to the server (192.168.1.96) from my desktop (192.168.1.97).
* I'm able to ssh to the desktop from the server.
* I'm able to ping from the server to the phone (192.168.1.122).
* I can access the web server running on the phone from my desktop.
* arping: server -> router: 8 probes, received 8 responses
* arping: desktop -> server: sent 8 probes, received 8 responses
* arping: server -> desktop: sent 8 probes, received 8 responses
* arping: desktop -> phone: sent 8 probes, received 8 responses
* arping: server -> phone: sent 5 probes, received 1 response
Run it multiple times - always receives 1 response.
* I ran tcpdump on the server to capture packets and I can see the ARP request.
 
Old 08-28-2012, 03:39 PM   #8
Jamie Royer
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Turns out my problem was related to a router issue. My router was running DD-WRT in "client bridge" mode and that seems to affect the ARP packet.

The phone was generating ARP packets that are 60 bytes in size (18 bytes of padding) where as the Ubuntu machines generated ARP packets that are 42 bytes in size.

I modified the router to use WDS (Wireless Distribution System) and it is now working correctly.
 
Old 11-22-2012, 05:15 AM   #9
srijit92
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Not working for me in 12.04.

Its not showing in ifconfig. Firmware installed.
 
  


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