05-09-2019 10:50 AM - edited 05-09-2019 10:52 AM
I am trying to understand the DNS lookup order on the router.
Let's say I have the following config:
ip host aaa.com 1.1.1.1
ip name-server 8.8.8.8
when I try to ping:
#ping aaa.com
Translating "aaa.com"...domain server (8.8.8.8)
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
!!!!
Clearly, aaa.com is not 1.1.1.1. I see my config overrides Google's 8.8.8.8. This makes sense. But what bothers me is that it still tries to resolve through 8.8.8.8. If I put in a non-existing DNS server:
no ip name-server 8.8.8.8
ip name-server 25.25.25.25
It clearly still try to resolve
#ping aaa.com
Translating "aaa.com"...domain server (25.25.25.25) <<---- long wait here
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 24/29/36 ms
What can I do to prevent that DNS lookup from happening and slowing down my local DNS resolution?
05-09-2019 11:48 AM
Cisco Router can Act as DNS Server for your Client. But most of FQDN it uses DNS resolution.
my view from FQDN lookup always uses the name server. but i belive local user want to access local server.
they should be like example :
ip host aaa.local 1.1.1.1
if you want to IOS Device act as DNS Server follow below document :
05-10-2019 10:59 AM
What I want to do is use external server for DNS lookup. The IOS router also acts as a DNS server and I want it to resolve some local DNS names. The aaa.com config is just an example to illustrate the problem. I want the IOS DNS server to simply return the static IP without performing another DNS query because it takes time especially when DNS serve is not reachable.
05-10-2019 04:20 PM
Hello
@pingduck wrote:
. I want the IOS DNS server to simply return the static IP without performing another DNS query because it takes time especially when DNS serve is not reachable.
no ip domain-lookup
05-10-2019 12:48 PM - edited 05-10-2019 03:43 PM
(removed due to duplicate)
05-10-2019 11:58 AM
What device and software version are you trying this on? It may depend on platform/software. Trying it on a CSR1000v 3.13.5 I get a different result than you are getting.
ip host aaa.com 1.1.1.1
ip name-server 8.8.8.8
R25#ping aaa.com
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 1.1.1.1, timeout is 2 seconds:
If i remove "ip host aaa.com 1.1.1.1"....
R25#ping aaa.com
Translating "aaa.com"...domain server (8.8.8.8)
05-10-2019 03:43 PM
Thanks. Looks like it maybe OS specific. I'm running 15.8(3)M0a (Classic IOS, not IOS-XE). Bummer!
05-11-2019 12:17 AM
i was thought the same due to old IOS.
Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: