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Full Discussion: necessary ARP request?
Special Forums IP Networking necessary ARP request? Post 302603975 by Corona688 on Friday 2nd of March 2012 12:51:38 PM
Old 03-02-2012
Quote:
Originally Posted by daWonderer
I started 'tcpdump' on wonder that host2 got ARP requests for 192.168.5.10.
Any idea why host1 asks for an IP of own system?
A smart DHCP client is paranoid and doesn't trust the values its given. It checks if they're occupied, first. (run dhcpcd manually, it'll even tell you it's doing so...)

Which is why a process which is theoretically near-instant can take many tedious seconds.
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IFNDP-PROXY(5)						       Network configuration						    IFNDP-PROXY(5)

NAME
ifndp-proxy[-<interface name>] - IPv6 NDP and IPv4 ARP proxy entries SYNOPSIS
/etc/sysconfig/network/ifndp-proxy /etc/sysconfig/network/ifndp-proxy-<interface name> DESCRIPTION
These files contain IPv6 NDP and IPv4 ARP proxy settings, that should be applied using the ip neigh add proxy command documented in the ip(8) manual page that provides a common interface for IPv4 and IPv6. The NDP/ARP proxy is required, e.g. when IP addresses from the same subnet have to be used on the interface of the host as well as on interfaces behind a (tunnel) interface and using a bridge is not an option. Don't forget to enable forwarding and the NDP/ARP proxy by setting net.ipv6.conf.<all|default|interface name>.proxy_ndp = 1 net.ipv6.conf.<all|default|interface name>.forwarding = 1 and/or net.ipv4.conf.<all|default|interface name>.proxy_arp = 1 net.ipv4.conf.<all|default|interface name>.forwarding = 1 or net.ipv4.ip_forward = 1 either as global all setting in the /etc/sysctl.conf file or using the ifsysctl(5) files, that allow per-interface setup. Forwarding can be also enabled in the /etc/sysconfig/sysctl file using the IP_FORWARD and IPV6_FORWARD variables. The proxy entries are added and deleted using the if-{up|down}.d/ndp-proxy script, every time after an involved interface has been set up or down. SYNTAX
The format of the ifndp-proxy file is: <address> <address interface> <proxy interface list> The format of the ifndp-proxy-<address interface> file is same to above, but allows also to omit the address interface by using a "-" as placeholder inside of the file, because it is already available in the file name: <address> <address interface | -> <proxy interface list> Lines beginning with # and blank lines are ignored. Each line defines to add a proxy NDP/ARP entry with the address of or behind address interface to all interfaces in the proxy interface list. EXAMPLES
Let's assume, your machine is connected via eth0 to a switch with the networks 2001:db8:abba::/64 and 192.168.100.1/24 and is using the IP address 1 itself. You'd like to use the addresses 11 and 12 e.g. for virtual machines behind the tap1 and tap2 interface, that is: 2001:db8:abba::1/64 -- local eth0 address 2001:db8:abba::11/64 -- address behind tap1 2001:db8:abba::12/64 -- address behind tap2 192.168.100.1/24 -- local eth0 address 192.168.100.11/24 -- address behind tap1 192.168.100.12/24 -- address behind tap2 then set up the following entries in the ifndp-proxy file: 2001:db8:abba::1 eth0 tap1 tap2 2001:db8:abba::11 tap1 eth0 tap2 2001:db8:abba::12 tap2 eth0 tap1 192.168.100.1 eth0 tap1 tap2 192.168.100.11 tap1 eth0 tap2 192.168.100.12 tap2 eth0 tap1 additionally to the routing entries in the routes or ifroute-<interface name> files. BUGS
Please report bugs at <https://bugzilla.novell.com/> AUTHOR
Marius Tomaschewski <mt@suse.de> SEE ALSO
ifup(8) ifcfg(5) ifsysctl(8) sysconfig December 2009 IFNDP-PROXY(5)
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