pavement

BIND, dynamic DNS, failover A records

From FreeBSDwiki
(Difference between revisions)
Jump to: navigation, search
(Remove spam about goodville from user DavidYoung.)
(minor updates)
Line 111: Line 111:
  
 
Perfect!  Now, the BSDcompany folks force an apparent fail condition on WAN2 to make sure it  ... \n
 
Perfect!  Now, the BSDcompany folks force an apparent fail condition on WAN2 to make sure it  ... \n
 +
 +
== White dress, green wedding ==
 +
 +
Lindsey Gehl and Ryan Bell have a vision of their June wedding being white - and green, too.The 27-year-olds will pledge their troth in a traditional ceremony, followed by a reception amid the scenic trails and wildlife habitats of the Pilcher Park Nature Center in Joliet, Illinois, to which theyre donating $600.
 +
 +
[[http://goodvillenews.com/White-dress-green-wedding-G3Qc3u.html White dress, green wedding]]
 +
 +
[[http://goodvillenews.com/wk.html GoodvilleNews.com - good, positive news, inspirational stories, articles]]
 +
 +
== 7 Choices You Always Have (that you dont always give yourself) ==
 +
 +
I believe the choice to be excellent begins with aligning your thoughts and words with the intention to require more from yourself. ~ Oprah WinfreyMaking choices is probably the most stressful thing that we do as humans. Or perhaps more accurately, the stressful thing we do is to choose avoidance when we dont like what choices were facing. This is what creates the stress.
 +
 +
[[http://goodvillenews.com/7-Choices-You-Always-Have-that-you-dont-always-give-yourself-RRF.html 7 Choices You Always Have (that you dont always give yourself)]]
 +
 +
[[http://goodvillenews.com/wk.html GoodvilleNews.com - good, positive news, inspirational stories, articles]]
 +
 +
== Stop Using The Wrong Type of Intelligence ==
 +
 +
A man should hear a little music, read a little poetry, and see a fine picture every day of his life, in order that worldly cares may not obliterate the sense of the beautiful which God has implanted in the human soul. Johann Wolfgang von Goethe
 +
 +
[[http://goodvillenews.com/Stop-Using-The-Wrong-Type-of-Intelligence-6IGOxm.html Stop Using The Wrong Type of Intelligence]]
 +
 +
[[http://goodvillenews.com/wk.html GoodvilleNews.com - good, positive news, inspirational stories, articles]]
 +
 +
== Not a Fairytale: Americas First Public Food Forest ==
 +
 +
Hungry? Just head over to the park. Seattles new food forest aims to be an edible wilderness. Seattles vision of an urban food oasis is going forward. A seven-acre plot of land in the citys Beacon Hill neighborhood will be planted with hundreds of different kinds of edibles
 +
 +
[[http://goodvillenews.com/Not-a-Fairytale-Americas-First-Public-Food-Forest-N18Amw.html Not a Fairytale: Americas First Public Food Forest]]
 +
 +
[[http://goodvillenews.com/wk.html GoodvilleNews.com - good, positive news, inspirational stories, articles]]
 +
 +
== The Importance of Learned Optimism ==
 +
 +
What 25 years of research reveal about the cognitive skills of happiness and finding lifes greater purpose.The illiterate of the 21st century, Alvin Toffler famously said, will not be those who cannot read and write, but those who cannot learn, unlearn, and relearn. Our outlook on the world and our daily choices of disposition and behavior are in many ways learned patterns to which Tofflers insight applies with all the greater urgency
 +
 +
[[http://goodvillenews.com/The-Importance-of-Learned-Optimism-jmZjsG.html The Importance of Learned Optimism]]
 +
 +
[[http://goodvillenews.com/wk.html GoodvilleNews.com - good, positive news, inspirational stories, articles]]

Revision as of 15:06, 12 August 2012

Contents

The problem: inexpensive but unreliable ISPs

If you've got a multi-homed network with multiple IP addresses from different ISPs, but you aren't a big enough organization to convince your ISPs to build BGP routes to connect to each other at your network, you will probably find it really handy to have a single DNS record that will automatically choose the best way to get to your network from the outside world.

In this example, "BSDcompany" runs a small office network (office.bsdcompany.com) and a server in a colocated network facility (coloserver.bsdcompany.com). Frequently, they need to access network resources inside the office from the internet. Since neither of the two ISPs available at BSDcompany's office are particularly reliable, BSDcompany has a cable modem from one of them, a DSL modem from the other, and a dual-WAN router. Both the cable and the DSL use dynamic IP addresses, and the company already has a server in the office doing dynamic DNS updates to cable-ip.office.bsdcompany.com and dsl-ip.office.bsdcompany.com.

BSDcompany's dual-WAN router provides load balancing and automatic failover redundancy for internet access from within the office. But BSDcompany wants similar redundancy and balancing from the outside coming in as well. So instead of randomly trying cable-ip.office.bsdcompany.com and dsl-ip.office.bsdcompany.com to see which (if either) is working at any particular time, they just want to be able to use a single name all the time and have it automatically take them to whichever ISP is up and/or faster at the moment.

The solution: ddns-failover.pl (another freebsdwiki.net original)

BSDcompany decides to set up a cron job on their colo server to check the status and latency of each of their office WAN IPs. That script will then automatically update a third A record, office.bsdcompany.com, with whichever is currently the quicker of the two office WANs to respond - and if both WANs are down, it will delete the record entirely until one or the other of them comes back up.

(Like the set-ddns.pl script in the previous dynamic DNS article, the variables ddns-failover.pl in UPPERCASE are things you should set to match your own situation, while the ones in lower or mixed case are generally things you shouldn't need to mess with.)

#!/usr/bin/perl

# ddns-failover.pl
#
# Copyright (c) 05-20-2006, JRS System Solutions
# All rights reserved under standard BSD license
# details: http://www.opensource.org/licenses/bsd-license.php
#
# Check each of two public IPs for the same multi-homed host,
# and set a dynamic DNS A record to point to the lower latency
# of the two.  If both routes are down, delete the hostname
# entirely until one or both IPs come back up.

$WANDNS1 = 'cable-ip.office.bsdcompany.com';
$WANDNS2 = 'dsl-ip.office.bsdcompany.com';
$HOSTNAME = 'office.bsdcompany.com';
$NAMESERVER = 'coloserver.bsdcompany.com';
$KEYFILE = 'Koffice.bsdcompany.com.+157+15661.private';
$KEYDIR = '/usr/home/ddns';
$TTL = '10';

@wan1 = split(/\n/,`/sbin/ping -qc 1 -t 1 $WANDNS1`);
@wan2 = split(/\n/,`/sbin/ping -qc 1 -t 1 $WANDNS2`);

$wan1[0] =~ /\((\d*?\.\d*?\.\d*?\.\d*?)\)/;
$wan1_ip = $1;
if ($wan1_ip == '') { $wan1_ip = 'NO HOST FOUND'; }
$wan2[0] =~ /\((\d*?\.\d*?\.\d*?\.\d*?)\)/;
$wan2_ip = $1;
if ($wan2_ip == '') { $wan2_ip = 'NO HOST FOUND'; }

$wan1[3] =~ /(\d*?) packets received/;
$wan1_rcvd = $1;
$wan2[3] =~ /(\d*?) packets received/;
$wan2_rcvd = $1;

$wan1[4] =~ /\/(\d*?\.\d*?)\//;
$wan1_time = $1;
$wan2[4] =~ /\/(\d*?\.\d*?)\//;
$wan2_time = $1;

if ($wan1_rcvd != 1 && $wan2_rcvd == 1) {
        print "WAN1 [$wan1_ip]: NO RESPONSE\nWAN2 [$wan2_ip]: $wan2_time" . "ms\nSET $HOSTNAME: WAN2\n";
        $dnsip=$wan2_ip;
} elsif ($wan1_rcvd == 1 && $wan2_rcvd != 1) {
        print "WAN1 [$wan1_ip]: $wan1_time" . "ms\nWAN2 [$wan2_ip]: NO RESPONSE\nSET $HOSTNAME: WAN1\n";
        $dnsip=$wan1_ip;
} elsif ($wan1_rcvd != 1 && $wan2_rcvd !=1) {
        print "WAN1 [$wan1_ip]: NO RESPONSE\nWAN2 [$wan2_ip]: NO RESPONSE\nDELETE $HOSTNAME\n";
        $dnsip='NO';
} elsif ($wan1_time <= $wan2_time) {
        print "WAN1 [$wan1_ip]: $wan1_time" . "ms\nWAN2 [$wan2_ip]: $wan2_time" . "ms\nSET $HOSTNAME: WAN1\n";
        $dnsip=$wan1_ip;
} else {
        print "WAN1 [$wan1_ip]: $wan1_time" . "ms\nWAN2 [$wan2_ip]: $wan2_time" . "ms\nSET $HOSTNAME: WAN2\n";
        $dnsip=$wan2_ip;
}

chdir ($KEYDIR);
open (NSUPDATE, "| /usr/sbin/nsupdate -k $KEYFILE");
print NSUPDATE "server $NAMESERVER\n";
print NSUPDATE "update delete $HOSTNAME A\n";
if ($dnsip ne 'NO') {
        print NSUPDATE "update add $HOSTNAME $TTL A $dnsip\n";
}
# print NSUPDATE "show\n";
print NSUPDATE "send\n";
close (NSUPDATE);

Setting up permissions

To minimize security risks, the gurus at BSDcompany create a new user named "ddns", put this script and the copies of the key files for the zone (which they already had, when they set up their dynamic DNS earlier) in the "ddns" user's home directory, and make sure to set the permissions on everything as restrictively as possible before setting up the cron job to actually run it.

coloserver# pw useradd ddns -s /sbin/nologin -d /usr/home/ddns
coloserver# mkdir /home/ddns
coloserver# cp /etc/namedb/zones/keys/Koffice.bsdcompany.com.+157+15661.private .
coloserver# cp /etc/namedb/zones/keys/Koffice.bsdcompany.com.+157+15661.key .
coloserver# chmod 400 Koffice.bsdcompany.com.+157+15661.*
coloserver# chmod 500 ddns-failover.pl
coloserver# ls -l
-r--------  1 ddns  wheel   130 May 20 12:22 Kph34r.tehinterweb.net.+157+23266.key
-r--------  1 ddns  wheel   145 May 20 13:17 Kph34r.tehinterweb.net.+157+23266.private
-r-x------  1 ddns  wheel  3108 May 23 01:27 ddns-failover.pl
coloserver# 'su ddns
This account is currently not available.

Excellent: the ddns account is present but cannot be interactively logged into, the key files are readable (but not writeable or executable) only to it, and the script is executable (but not writeable) only to it. Now that the permissions are correct, it's time to do a test run - we'll run the script manually (using sudo to do so as the user ddns, just like the cron job will) before we set it up to run automatically.

Testing the script manually

coloserver# sudo -u ddns /usr/bin/perl /usr/home/ddns/ddns-failover.pl
WAN1 [128.32.64.5]: 94.302ms
WAN2 [144.69.42.18]: 85.341ms
SET office.bsdcompany.com: WAN2
coloserver# ping -qc 1 office.bsdcompany.com
PING office.bsdcompany.com (144.69.42.18): 56 data bytes

--- office.bsdcompany.com ping statistics ---
1 packets transmitted, 1 packets received, 0% packet loss
round-trip min/avg/max/stddev = 85.038/85.038/85.038/0.000 ms

Perfect! Now, the BSDcompany folks force an apparent fail condition on WAN2 to make sure it ... \n

White dress, green wedding

Lindsey Gehl and Ryan Bell have a vision of their June wedding being white - and green, too.The 27-year-olds will pledge their troth in a traditional ceremony, followed by a reception amid the scenic trails and wildlife habitats of the Pilcher Park Nature Center in Joliet, Illinois, to which theyre donating $600.

[White dress, green wedding]

[GoodvilleNews.com - good, positive news, inspirational stories, articles]

7 Choices You Always Have (that you dont always give yourself)

I believe the choice to be excellent begins with aligning your thoughts and words with the intention to require more from yourself. ~ Oprah WinfreyMaking choices is probably the most stressful thing that we do as humans. Or perhaps more accurately, the stressful thing we do is to choose avoidance when we dont like what choices were facing. This is what creates the stress.

[7 Choices You Always Have (that you dont always give yourself)]

[GoodvilleNews.com - good, positive news, inspirational stories, articles]

Stop Using The Wrong Type of Intelligence

A man should hear a little music, read a little poetry, and see a fine picture every day of his life, in order that worldly cares may not obliterate the sense of the beautiful which God has implanted in the human soul. Johann Wolfgang von Goethe

[Stop Using The Wrong Type of Intelligence]

[GoodvilleNews.com - good, positive news, inspirational stories, articles]

Not a Fairytale: Americas First Public Food Forest

Hungry? Just head over to the park. Seattles new food forest aims to be an edible wilderness. Seattles vision of an urban food oasis is going forward. A seven-acre plot of land in the citys Beacon Hill neighborhood will be planted with hundreds of different kinds of edibles

[Not a Fairytale: Americas First Public Food Forest]

[GoodvilleNews.com - good, positive news, inspirational stories, articles]

The Importance of Learned Optimism

What 25 years of research reveal about the cognitive skills of happiness and finding lifes greater purpose.The illiterate of the 21st century, Alvin Toffler famously said, will not be those who cannot read and write, but those who cannot learn, unlearn, and relearn. Our outlook on the world and our daily choices of disposition and behavior are in many ways learned patterns to which Tofflers insight applies with all the greater urgency

[The Importance of Learned Optimism]

[GoodvilleNews.com - good, positive news, inspirational stories, articles]

Personal tools