Tuesday, December 3, 2013

strong host/weak host

One problem when you multihome and you do selective routing (the default gateway is NOT configured on all interfaces) say multiple VRFs is a deal called strong host/weak host. It can prevent one of the NIC from responding from pings from the rest of the network even if it does work in its VRF. http://technet.microsoft.com/en-us/magazine/2007.09.cableguy.aspx The default for windows 2008 is called strong host, that means that you cannot send a packet with a source IP address different than the IP address of the interface. Since we are trying to ping a backup VRF ip address from outside the backup vrf, the host has to send the ping reply out the public interface and strong host will not allow that. Could be the setting got lost in the standard build. to fix netsh interface ipv4 set interface [InterfaceNameOrIndex] weakhostsend=enabled

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