Messages in this thread | | | Date | Fri, 20 Aug 1999 13:09:47 -0400 (EDT) | From | Chris Leech <> | Subject | ARP (mis)behavior |
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I'm doing some work with network drivers, and have run across some strange ARP behavior in testing that seems to stem from the IPv4 stack. ARP replies seem to ignore any mapping between devices and IP addresses, so that as long as an IP is assigned to one interface all the interfaces on a given machine will respond to the ARP request.
As a simple example, if a server has two Ethernet cards connected to the same network configured as 10.0.0.1 and 10.0.0.2. From a client machine, say 10.0.0.3, pinging both server addresses seems to work, but looking at the ARP cache reveals that often one interface has responded to both ARP requests. More interesting, if one interface is brought down the other will continue to respond to ARP requests and any other network traffic for the downed adapters IP address.
In a situation where multiple adapters are on the same network segment, the Linux IPv4 stack behaves as if a many-to-many mapping of a pool of IP addresses onto a pool of network adapters exists.
While this does provide some basic fail-over capabilities, I can't imagine that this is expected or desired behavior. If this is the intended behavior, I'd be interested in hearing why ARP was implemented this way. If not, I may have time to try and change this and submit a patch.
(note: I'm having trouble sending to the list from my Intel account, please ignore the fact that I'm sending from my mail.com account)
Chris Leech christopher.leech@intel.com Intel Network Communications Group
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