07-26-2009 05:20 PM - edited 03-06-2019 06:57 AM
int FastEthernet0/0
description inside
ip address i.i.i.i m.m.m.m
int FastEthernet0/1
description outside1 to ISP#1 with DNS0 o.o.o.1 and DNS1 o.o.o.2
ip address dhcp
int FastEthernet0/2
description outside2 to ISP#2 with DNS0 o.o.o.3 and DNS1 o.o.o.4
ip address dhcp
... sla configured so if outside1 goes down outside2 is selected
... now what I want to do is to set this router to act as a DNS server on i.i.i.i (as stated on inside):
ip dns server ... this server should respond to local hosts such as:
ip domain name whatever.com
ip host computer1 x.x.x.x
ip host computer2 x.x.x.x
ip host computer3 x.x.x.x
... and this server should forward unknown hosts to the DNS servers stated on the current outside connection
if outside1 is active local DNS server should forward to o.o.o.1 o.o.o.2
if outside2 is active local DNS server should forward to o.o.o.3 o.o.o.4
while my internal DNS server will always point to i.i.i.i knowing nothing about which ISP is active at any given moment
... so; how do I set the DNS forwarders to the ones assigned by the active dhcp lease ?
why this ?
because I can place just one forwarder (i.i.i.i) on my internal AD DNS server and forget about what ISP I'm connected at any moment, otherwise I have to manually change the DNS list on my Windows box everytime I switch over to the other ISP with its associated DNS servers
eg:
sh dhcp server
DHCP server: ANY (255.255.255.255)
Leases: 2
Offers: 1 Requests: 1 Acks : 2 Naks: 0
Declines: 0 Releases: 0 Query: 0 Bad: 0
DNS0: o.o.o.1, DNS1: o.o.o.2
Subnet: 255.255.255.0
sh dhcp lease
Temp IP addr: 192.168.1.101 for peer on Interface: ...
Temp sub net mask: 255.255.255.0
DHCP Lease server: 192.168.1.1, state: 5 Bound
DHCP transaction id: 1D81
Lease: 741 secs, Renewal: 370 secs, Rebind: 648 secs
Temp default-gateway addr: 192.168.1.1
Next timer fires after: 00:05:46
Retry count: 0 Client-ID: ...
Client-ID hex dump: ...
Hostname: ...
Temp IP addr: 0.0.0.0 for peer on Interface: ...
Temp sub net mask: 0.0.0.0
DHCP Lease server: 0.0.0.0, state: 11 Purging
DHCP transaction id: 1D82
Lease: 0 secs, Renewal: 0 secs, Rebind: 0 secs
Next timer fires after: 00:00:30
Retry count: 0 Client-ID: ...
Client-ID hex dump: ...
Hostname: ...
I want something set like [ip dns forwarder o.o.o.1 o.o.o.2] so nslookup site.com i.i.i.i should return the appropriate address using my router
can somebody point me in the right direction ?
07-27-2009 08:37 AM
... self-solved but not sure if it's the right/optimal way:
ip dns view default
no domain lookup
no dns forwarding
ip dns view dnsVedge
domain name whatever.com
domain name-server interface FastEthernet0/1
domain resolver source-interface FastEthernet0/0
domain round-robin
ip dns view-list dnsVLedge
view dnsVedge 1
ip dns server view-group dnsVLedge
ip dns server
... default view not used; using dnsVedge instead:
sh ip dns view
DNS View dnsVedge parameters:
Logging is off
DNS Resolver settings:
Domain lookup is enabled
Default domain name: whatever.com
Domain search list:
Lookup timeout: 3 seconds
Lookup retries: 2
Domain name-servers:
o.o.o.1
o.o.o.2
Resolver source interface: FastEthernet0/0/0
Round-robin'ing of IP addresses is enabled
DNS Server settings:
Forwarding of queries is enabled
Forwarder addresses:
DNS View default parameters:
Logging is off
DNS Resolver settings:
Domain lookup is disabled
Default domain name: whatever.com
Domain search list:
Lookup timeout: 3 seconds
Lookup retries: 2
Domain name-servers:
o.o.o.1
o.o.o.2
DNS Server settings:
Forwarding of queries is disabled
Forwarder addresses:
... right now it's working fine with both ISPs
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