Home / server / Questions / 322590
Accepted
agsamek
Asked: 2011-10-19 07:09:26 +0800 CST

what IP address can I ping as a watchdog target for load balancer?

  • 772

I'm setting up a load balancer for my network. I have three options to select as a verification method if WAN is still alive:

  1. Link Up (whether a modem is alive). This doesn't work for me because modem is alive even if a line is down.

  2. IP Address for Ping. I would like to use this but I don't know what server should I choose.

  3. DNS Lookup. This also may be an option.

Shall I select Ping or DNS? In both cases - what IP address should I use? (I cannot use a domain name - I need an IP address)

domain-name-system load-balancing ping

2 Answers

  1. Do a traceroute to a remote destination and try to ping one of the first hops after your modem.

    • 5
  2. Best Answer

    I would go with Option 2: Ping 8.8.8.8 (Google Public DNS "A")
    This breaks if 8.8.8.8 ever goes away or Google blocks ICMP Echo requests/replies -- Not likely at the moment. It has the benefit of also testing your routing to a host that should be reachable from anywhere.

    Using DNS to test connectivity has "other issues" (ISPs that take over your DNS and send their own shit instead of NXDOMAIN like God and Mockapetris intended ; Your target domain expiring and causing your network link to appear "down" ; etc.)

    • 5