Bonnell, David
2005-Dec-22 21:51 UTC
RE: [Xen-devel] RE: [patch, rfc] put IP addresses into xenstore (Gerd Knorr)
Arping sends ARP "who-has" requests, either broadcast or directed to a specific MAC address and displays the responses. I retrieve the MAC address of each VIF of each domain from XenStore and use arping to obtain the associated IP address. http://freshmeat.net/projects/arping/ Regards, David Bonnell Corporate Architect BMC Software -----Original Message----- From: Gerd Knorr [mailto:kraxel@suse.de] Sent: Thursday, 22 December 2005 10:48 AM To: Bonnell, David Cc: xen-devel@lists.xensource.com Subject: Re: [Xen-devel] RE: [patch, rfc] put IP addresses into xenstore (Gerd Knorr) Bonnell, David wrote:> I have been using arping to do a reverse ARP on the MAC address(es) to > obtain the IP address(es) used by each domain but this will be easier.How does that work? What I''ve found depends on either the host replying to broadcast pings or on brute-force, i.e. try every IP address in the network (which isn''t exactly nice, especially in a /16 ...). cheers, Gerd _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel
Gerd Knorr
2005-Dec-23 13:48 UTC
Re: [Xen-devel] RE: [patch, rfc] put IP addresses into xenstore (Gerd Knorr)
Bonnell, David wrote:> Arping sends ARP "who-has" requests, either broadcast or directed to a > specific MAC address and displays the responses.No. It does that if you ping an IP address, but not if you ping a MAC address. For pinging mac addresses it sends a ICMP ping, to the MAC address specified, with broadcast (IP-)address as destination in the header. And thats exactly the problem, machines tend to not respond to broadcast pings for security reasons (allows certain kinds of DoS attacks), so this isn''t going to work reliable. Try "echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_broadcasts" in your domU and receiving the IP address with arping doesn''t work any more ... Another problem is that there are multiple arping versions out there, for example the iputils ship an arping utility to, and that one doesn''t even support pinging hosts by MAC address. cheers, Gerd _______________________________________________ Xen-devel mailing list Xen-devel@lists.xensource.com http://lists.xensource.com/xen-devel