Re: Problem with network interface

[Steven Bellovin <smb%cs.columbia.edu@localhost>]

On Jul 1, 2011, at 4:57 28AM, Konrad Neuwirth wrote:

> Dear reader, 
> 
> I have a network problem on a system running NetBSD 5.1 that I do not fully 
> understand. We have an interface wm2 that is configured as follows: 
> 
> wm2: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
>        
> capabilities=7ff80<TSO4,IP4CSUM_Rx,IP4CSUM_Tx,TCP4CSUM_Rx,TCP4CSUM_Tx,UDP4CSUM_Rx,UDP4CSUM_Tx,TCP6CSUM_Rx,TCP6CSUM_Tx,UDP6CSUM_Rx,UDP6CSUM_Tx,TSO6>
>        
> enabled=3f80<TSO4,IP4CSUM_Rx,IP4CSUM_Tx,TCP4CSUM_Rx,TCP4CSUM_Tx,UDP4CSUM_Rx,UDP4CSUM_Tx>
>        address: 00:15:17:b1:b7:ff
>        media: Ethernet autoselect (100baseTX 
> full-duplex,flowcontrol,rxpause,txpause)
>        status: active
>        inet 192.168.100.1 netmask 0xffffff00 broadcast 192.168.100.255
>        inet6 fe80::215:17ff:feb1:b7ff%wm2 prefixlen 64 scopeid 0x3
> 
> Directly connected to it is a second machine, currently configured as 
> 192.168.100.2. We're trying to send pings back and forth. 
> Ipmon tells us these things are even successful: 
> 
> Jul  1 10:56:26 pinie ipmon[24589]: 10:56:25.847016 wm2 @0:2 p 192.168.100.2 
> -> 192.168.100.1 PR icmp len 20 60 icmp echo/0 IN
> Jul  1 10:56:26 pinie ipmon[24589]: 10:56:25.847023 wm2 @0:2 p 192.168.100.1 
> -> 192.168.100.2 PR icmp len 20 60 icmp echoreply/0 OUT
> 
> Alas, dmesg reports something else: 
> 
> arplookup: unable to enter address for 192.168.100.2@00:24:54:de:59:bd on wm2 
> (host is not on local network)
> 
> Of course, this leads to no packets ever reaching the destination. 
> 
> What am I missing? Why can't the address be entered into the arp table? 
> 
What do your other interfaces look like?  What does the routing table look like?


                --Steve Bellovin, https://www.cs.columbia.edu/~smb