On 2012-05-16, Russell Garrison <russell.garri...@gmail.com> wrote: >> On Wed, May 16, 2012 at 9:40 AM, Indunil Jayasooriya >> <induni...@gmail.com> wrote: > >>> If yes, How to ping external internet host when that link is DOWN? I find >>> it difficult? >>> >>> I tried it with below commands >>> >>> >>> ping -I WAN1_if_ip www.google.lk >>> >>> ping -I WAN2_if_ip www.google.lk >>> >>> >>> Some times it works? some times it does NOT? >>> >>> Could you pls explain why?
Route lookups are based on the *destination* address not the source address, you could add a route for a certain destination via a certain interface to send packets out that way. > I have been asked by management a few times about why some pings fail > when you ping things like google servers and core routers at the ISP. Management might need to set the TOS bits. ping -T i_am_management_my_packets_are_important_dammit www.google.com If they are really important they can use -i0.0001 -e to be sure people pay attention. Needs root but they are probably logged in like that already, right? :) > The short answer I give is that things like that are too busy being > the Internet to respond to all the ping traffic that doesn't do > anything to enable them to be the Internet. Best advice is to consult > your routing tables or contact your ISP and have your ifstated ping > the far-end of your internet connection. Those systems are typically > less busy and have a higher expectation of answering all pings while > up. "far-end of your internet connection" tends to be a router, which are usually one of the worst things to be pinging, something like a local web or ntp server might be a better idea.
