Date: Thu, 11 Jul 1996 18:13:33 -0700 From: Pius Fischer <pius@iago.ienet.com> To: freebsd-hackers@FreeBSD.ORG Cc: terryl@ienet.com Subject: bizarre network problem Message-ID: <199607120113.SAA25317@iago.ienet.com>
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We've been experiencing a strange network problem with a machine running FreeBSD 2.1-stable. Any help would be greatly appreciated. Here's out setup: ---------------------- | portia.ienet.com | ---------------------- ------------------- | Pentium 166 MHz |----|3Com LinkSwitch 1000|--|gate.ienet.com |--> UUNet | FreeBSD 2.1-STABLE | ---------------------- |Cisco 2500 series| ---------------------- ------------------- So, we've got a Cisco connecting us to the Internet via a T-1. The Cisco connects to our Ethernet hub (the LinkSwitch) via 10 Mb/s Ethernet and the LinkSwitch connects to the host portia via 100 Mb/s Ethernet. We've also got a few other hosts connected to the LinkSwitch. The problem is that every once in a while packets coming from the outside (coming in through our Cisco) don't make it to portia. This happens usually whenever there is little network traffic to portia for a period of time. traceroutes from the outside will get to the Cisco but not to portia. We put the Cisco into debugging mode (with 'debug ip packet') and it appears to correctly forward the packets to portia, but a tcpdump process running on portia never showed us any of those packets. This problem never occurs with packets sent from any of the other hosts connected to the Ethernet hub. In fact, if I ping or telnet to portia from one of these local hosts, portia appears to magically wake up and process all packets correctly. And if I'm on portia's console and do an 'arp -a', normally I get a quick response and see the arp cache. However, if this problem is happening, then doing an 'arp -a' takes about 3 or 4 seconds before showing me the cache and, again, portia wakes up and all packets are received and replied to. It appears that at the time the problem is happening, the arp cache entry for the Cisco is incomplete, but that is probably just because it expired and so shouldn't portia just reissue an arp query? Well, I guess it wouldn't if it's not receiving anything to prompt the query. So the question is, is this a problem with the kernel or with our LinkSwitch or with something else? What does 'arp -a' do that could cause the kernel to wake up? It never fails to receive local packets like RIP updates every 30 seconds and broadcast ARP queries, etc., but those, unlike the ping or telnet don't cause it to wake up to remote traffic. portia uses an Intel EtherExpress PRO/100 LAN Adapter and the fxp0 device driver. Any ideas? Thanks, Pius
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