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Destination NAT

Ali Hazim
Level 1
Level 1

Hello Everyone,

I have an ASR1006 on which I've configured a virtual template for PPPoE connection and  applied NAT config for  the PPPoE clients to access the internet.

Is there a  way to create a destination NAT for all DNS traffic to be redirected toward 8.8.8.8, so that if a PPPoE client sets the DNS on their device to any value other than (8.8.8.8), the ASR  will force the traffic to go to 8.8.8.8.

So assume the PPPoE Clients range is 100.64.0.0/10, I want all the traffic that has:
Source IP (100.64.0.0/10) and destination IP (0.0.0.0/0) on UDP port  53
To be redirected to be:
Source IP (100.64.0.0/10) and destination IP (8.8.8.8) on UDP port  53

2 Replies 2

Will this idea I think will work

But the best is apply acl to drop any packet use l4 udp port 53 to any destiantion other than 8.8.8.8 

This make user pc try any dnc failed and then use in end 8.8.8.8 this fallback is automatic.

MHM

Hello


@Ali Hazim wrote:
So assume the PPPoE Clients range is 100.64.0.0/10, I want all the traffic that has:

Source IP (100.64.0.0/10) and destination IP (0.0.0.0/0) on UDP port  53
To be redirected to be:
Source IP (100.64.0.0/10) and destination IP (8.8.8.8) on UDP port  53


You could try policy based routing so traffic is forwarded to the correct dns.

Example:
Ip access-list extended DNS
permit tcp 100.64.0.0 0.3.255.255 eq domain any

permit udp a100.64.0.0 0.3.255.255 eq domain any

route-map DNS_rm
match ip address DNS
set ip next-hop 8.8.8.8

interface x/x
description LAN interface
ip policy-route DNS_rm


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Kind Regards
Paul
Review Cisco Networking for a $25 gift card