Resolution slows down

[popeus]

I have a small website hosting company. The issue is I have two internet con
nections, internet connection 1 is dsl with static ip's. internet connection
2 is cable with static ip's.

Router is rv082, both connections plug into it and it handles web requests t
o port 80.

Two Win2k dns servers on dsl connection one primary and one secondary. Not c
onnected to router dns points to router's ip address for all domains.

One Win2k dns server on cable connection (secondary) Not connected to router
dns points to router's ip address for all domains.

dns0.domain.com
dns1.domain.com
dns2.domain.com
All are registered with root servers.

Both secondary servers are updated from the primary.

The dsl connection has always been the most stable. When the cable connectio
n goes down, and the dsl connection is still up the website respond extremly
slow.

I'm assuming it's the client trying to resolve the domain on the down connec
tion and it take a while for the client to get to the dns server that is up
to resolve the request. Any ideas.

Example zone file:
;
; Database file gulfshoreswebdesign.com.dns for gulfshoreswebdesign.com zon
e.
; Zone version: 16
;

@ IN SOA dns0.xorbmedia.com. admin.xorbmedia.com. (
16 ; serial number
900 ; refresh
600 ; retry
86400 ; expire
3600 ) ; minimum TTL

;
; Zone NS records
;

@ NS dns0.xorbmedia.com.
@ NS dns1.xorbmedia.com.
dns1.xorbmedia.com. A 216.231.181.243
@ NS dns2.xorbmedia.com.
dns2.xorbmedia.com. A 12.214.225.6

;
; Zone records
;

@ A 216.231.181.244
@ A 12.214.225.4
@ MX 10 mail.gulfshoreswebdesign.com.
@ MX 5 mail1.gulfshoreswebdesign.com.
gswd A 216.231.181.244
A 12.214.225.4
mail A 12.214.225.4
A 216.231.181.244
mail1 A 216.231.181.244
www CNAME gswd.gulfshoreswebdesign.com.

Second part of problem, is when one connection goes down, any client trying
to send or receive mail whose isp has cached the down connections' ip for th
e mail server can send or receive mail. Any way around this? The above record shows where I added a second mx record, but I don't know, if it's working or not.

 

[elgrandeperro]

I assume net 12 is your better connection (DSL), I could not discern from your listing. If not, just switch my analysis.

First, I would do the mail stuff using the standard MX mail precedence rules. Do not put both IPs on "mail", just

mail A 12.214.225.4
mail1 A 216.231.181.244

@ MX 5 mail.gulfshorewebdesign.com.
MX 10 mail1.gulfshorewebdesign.com.

When you put 2 ips (also like on your webserver), you
don't have any particular weighting on the records. By
default, it will round robin, giving both but in alternating order. Most TCP stacks will try the first, timeout and try the second. Look to see if you can give the IPs in fixed order, with the DSL first and the
cable second. The problem is that it will probably be cached in that order by the remote host, so when the DSL is truly down you will have an apparently slow server on the cable side.

One manual way to fix this is to only assign the DSL ip to www, but with a low TTL, like 10 minutes. Then if the cable goes down, you could manually switch the ips in DNS, and in 10 minutes the old ip will expire and the new ip should be in play. (I have heard that some ISPs ignore the TTL settings, which can lead to some head scratching).

gene