You're correct in that DNS on multiple IP subnets is recommended. I've never heard a recommendation to have them in separate pools from the web servers. Can't think of a justification for that.
I read from his scenario that he probably had all DNS in-house along with the web serves, thus having multiple IPs on separate subnets pointing to the same two or more servers meets that need. I agree that it would be better to have everything off-site. In this case, I don't think it matters much if DNS is unavailable if both lines go down since the web and email servers would also be unavailable. If only one line goes down, one possibility is the one you mentioned that DNS records would need to be changed if the primary line was down. For MX in that scenario, you could have two MX records for each IP subnet. For Web, you would need to have a load balancer outside of the dual WAN router that would detect a line down, or switch the records over. None of this is all that great. Another possibility is to have DNS servers dedicated to each line, with two separate sets of records. You would still want to have MX records for both subnets to avoid propagation issues, but this would handle the host records. If I were doing it this way, I'd probably keep a low TTL and have a kill switch that ran a script to change all of the DNS records when a line went down....but then I wouldn't do it this way...<grin> Bottom line is this would all be better off in a hosting center with proper lines, power, and security. Darin. ----- Original Message ----- From: "Imail Admin" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Thursday, July 22, 2004 6:28 PM Subject: Re: [IMail Forum] OT: Redundancy I'm still a little confused by how you're setting up the DNS servers in this plan. I can see that if his primary DNS servers are on the same line as his web servers, then when that connection goes down, those DNS servers also become unavailable. If he has the redundant line, with different DNS servers, then access is still available through that line and those DNS servers take over the work. However, what happens if he has independent DNS servers that are not residing locally? Generally, people don't recommend having all of your DNS servers in the same IP pool/same connection as your web servers. So he might have one or more secondary DNS servers that are located elsewhere (possibly another city or state). When his primary line goes down, those secondary DNS servers would still report the IP addresses belonging to that line, and not the IP addresses belonging to his backup line. What am I missing here? Ben BC Web ----- Original Message ----- From: "Darin Cox" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Sent: Thursday, July 22, 2004 8:19 AM Subject: Re: [IMail Forum] OT: Redundancy > While I would never recommend running a hosting op this way without > appropriate bandwidth/power redundancy and security, we used to run our > office similar to this. There's two possibilities that we tried at various > times that might work for you, depending on your budget: > > 1. The cheap solution: Set up an additional NS server record on all hosted > domains that uses the backup network WAN IP. So, when the primary network > is down, switch the cable over. DNS servers with addresses on the primary > network are unavailable, but DNS servers on the backup network are > available, and vice versa. > > 2. Preferably, set up a dual WAN router to aggregate the bandwidth from both > providers. You still need to set up the additional NS records, but in this > case all are online all of the time (except during an outage for one or the > other provider). A side benefit of this is that you have more bandwidth to > your office for normal use. This could also help with remote access to the > office in times of outage. > > HTH > > Darin. > > > ----- Original Message ----- > From: "Bill Pierson" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Thursday, July 22, 2004 11:00 AM > Subject: [IMail Forum] OT: Redundancy > > > This is a little off topic, but I think this may reach my intended audience > who may be able to offer some solutions. > We run a small web hosting company, and have a full T1 for our main > connection source. We generally have very little downtime, and our hosting > clients have come to appreciate that. For the second time in 2 months, > however, a major fiber line was cut and we had no phones or T1 for over 8 > hours. > I've gotten a cable-based "backup" connection and I'm trying to decide the > best possible way to implement it as a backup for when the T1 goes down > again. > I only want to use the cable-based solution when the T1 goes down; no > load-balancing is needed.... > I have a firewall in place and use NAT/reverse proxy so that sites will come > up from either (T1 or cable) Internet IP..... > > Has anyone had experience or could someone recommend a solution that would > handle DNS ? > For example, when our T1 is up and functioning, DNS points to our T1-based > IP's. When the T1 goes down, DNS gets pointed to our cable-based IP's. I > realize the TTL would have to be set low, but how low is too low? > > Again, sorry for the OT subject - any info will be sincerely appreciated. > --Bill > [EMAIL PROTECTED] > > > > To Unsubscribe: http://www.ipswitch.com/support/mailing-lists.html > List Archive: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ > Knowledge Base/FAQ: http://www.ipswitch.com/support/IMail/ > > > To Unsubscribe: http://www.ipswitch.com/support/mailing-lists.html > List Archive: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ > Knowledge Base/FAQ: http://www.ipswitch.com/support/IMail/ > To Unsubscribe: http://www.ipswitch.com/support/mailing-lists.html List Archive: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ Knowledge Base/FAQ: http://www.ipswitch.com/support/IMail/ To Unsubscribe: http://www.ipswitch.com/support/mailing-lists.html List Archive: http://www.mail-archive.com/imail_forum%40list.ipswitch.com/ Knowledge Base/FAQ: http://www.ipswitch.com/support/IMail/
