Messages in this thread |  | | Subject | Re: Linux 2.2 - BSD/OS 4.1 ARP incompatibility | Date | Tue, 05 Sep 2000 04:07:22 +1100 | From | David Luyer <> |
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> just try "traceroute -s 111.111.111.111 d.e.f.2"
> What shows this simple test? > > arp who-has d.e.f.2 tell a.b.c.1 > > or > > arp who-has d.e.f.2 tell d.e.f.1
When I tried traceroute -s d.e.f.1 d.e.f.2, it worked, the first time the Linux box in question talked to the BSD/OS in question without the aid of an extra host spoofing responses to the arp queries in question.
The command you suggested also had the desired effect. However...
# arp -d d.e.f.2 # traceroute d.e.f.2 traceroute to d.e.f.2, 30 hops max, 40 byte packets 1 a.b.c.1 2997 ms !H 2998 ms !H 3000 ms !H
(ie, failure by default)
# traceroute -s d.e.f.1 d.e.f.2 traceroute to d.e.f.2 from d.e.f.1, 30 hops max, 40 byte packets 1 d.e.f.2 1 ms 0 ms 0 ms # traceroute d.e.f.2 traceroute to d.e.f.2, 30 hops max, 40 byte packets 1 d.e.f.2 1 ms 0 ms 0 ms
(success, and success by default once the MAC address is known to the ARP table)
# arp -d d.e.f.2 # traceroute -s 5.5.5.5 d.e.f.2 1 * * *
at this point the tcpdump shows arp requests from d.e.f.1, ie, correct ARP requests.
But straight command line ping and traceroute with no explicit source, and sockets which are not explicitly bound (eg, standard netkit telnet) are perhaps being auto-bound or otherwise made to choose a.b.c.1 as their for arp requests.
> If the announced address is d.e.f.1 then there is no problem in > inet_select_addr() but your application is already bound to the > primary address.
It's not in the case of telnet (simple to see by strace), and I expect not in the case of traceroute with no explicit source either. However, perhaps the automatic bind is choosing the primary address.
So if I want it to work I most likely need to make the ARP request ignore the higher level bindings of the socket.
David. -- ---------------------------------------------- David Luyer Senior Network Engineer Pacific Internet (Aust) Pty Ltd Phone: +61 3 9674 7525 Fax: +61 3 9699 8693 Mobile: +61 4 1064 2258, +61 4 1114 2258 http://www.pacific.net.au NASDAQ: PCNTF << fast 'n easy >> ----------------------------------------------
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