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Author Topic: ARP broken after IP address change (squeeze)  (Read 4364 times)
samweber
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« on: March 31, 2011, 11:04:07 AM »

Followed these instructions for putting Debian Squeeze on my plug: http://www.cyrius.com/debian/kirkwood/sheevaplug/install.html

Works great.  Configured networking for one that has access to the internet for the installation.  Tested ARP, PING, and tftp functionality after the install completed.  Everything worked.

Modified /etc/network/interfaces and /etc/networks to point to the deployment private network.  Now the plug won't respond to ARP and appears to discard responses to its own ARP requests.  Verified with Wireshark that the ARP packets are valid.
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birdman
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« Reply #1 on: April 01, 2011, 02:27:49 PM »

Modified /etc/network/interfaces and /etc/networks to point to the deployment private network. 
/etc/hosts?
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samweber
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« Reply #2 on: April 02, 2011, 02:59:44 PM »

I modified it as well.  No joy.  Good catch though, birdman.  I didn't think of that one at first and found it by grepping for the IP address string.
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cbxbiker61
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« Reply #3 on: April 02, 2011, 09:41:59 PM »

Is firewalling enabled on the device?  Try disabling that and see how it behaves.

I had to disable firewalling on an OpenWrt router (it's internal) to get ARP passthrough working.
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samweber
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« Reply #4 on: April 04, 2011, 02:21:10 PM »

There are no firewall rules so I think the firewall is turned off.

root@sheeva1:/etc/init.d# /sbin/iptables -L
[339996.462728] ip_tables: (C) 2000-2006 Netfilter Core Team
Chain INPUT (policy ACCEPT)
target     prot opt source               destination         

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination 
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samweber
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« Reply #5 on: April 27, 2011, 12:26:27 PM »

Turns out that the problem was not limited to ARP.  The root problem was that all incoming packets were being dropped.

I learned how to rebuild a compatible kernel for this distribution (thanks pingtoo and cbxbiker61) and instrumented the ethernet driver so I could see what was causing the dropped packets.  The Receive Descriptor Command/Status register indicated a CRC Error on every receive packet.  I had earlier decided that the hub could not be bad because other devices connected to it work perfectly.  Here are the results of different connection setups (the PC connection in all these tests is via a Trendnet TU-ET100C USB to Ethernet Adapter):

1. Netgear DS104 hub - CRC error on every RX packet (tried two different ones).
2. Netgear EN104TP hub - CRC error on every RX packet.
3. Watchguard SOHO WG2500 - CRC error on every packet.
4. Crossover cable - No errors.
5. Netgear DS108 hub - No errors.
6. Kingston EtheRx Pro Series 24-port 10/100 dual speed hub - No errors.
7. Cisco BEFSR41 - No errors.
8. Netgear GS105 - No errors.

Alternate configuration that also worked:  Trendnet to DS104, DS104 to GS105, GS105 to plug.

Summary: Plug MAC doesn't seem to like some older network gear.
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