https://github.com/cdennig/custom-dns-aks
https://github.com/cdennig/custom-dns-aks
Last synced: 4 months ago
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- Host: GitHub
- URL: https://github.com/cdennig/custom-dns-aks
- Owner: cdennig
- Created: 2020-10-07T10:44:48.000Z (over 5 years ago)
- Default Branch: main
- Last Pushed: 2020-10-07T11:01:16.000Z (over 5 years ago)
- Last Synced: 2025-01-29T17:44:58.410Z (over 1 year ago)
- Size: 29.3 KB
- Stars: 0
- Watchers: 2
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# CoreDNS Test
## Add VM (just for demo purposes!)
Install Ubuntu-18-04 LTS
192.168.0.0/24
NSG:
---
In VM:
Get IP Adress:
```shell
$ ifconfig eth0
eth0: flags=4163 mtu 1500
inet 192.168.0.4 netmask 255.255.255.0 broadcast 192.168.0.255
inet6 fe80::20d:3aff:fe2d:a84a prefixlen 64 scopeid 0x20
ether 00:0d:3a:2d:a8:4a txqueuelen 1000 (Ethernet)
RX packets 135861 bytes 172074370 (172.0 MB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 28934 bytes 4777038 (4.7 MB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
```
--> 192.168.0.4
Install bind9:
```shell
sudo apt-get update
sudo apt-get install bind9 bind9utils bind9-doc
```
IPv4 Bind mode:
```shell
sudo vim /etc/default/bind9
...
OPTIONS="-u bind -4"
```
Restart sudo systemctl restart bind9
Check:
azureuser@mydnsserver:~$ ps -ax | grep named
14810 ? Ssl 0:00 /usr/sbin/named -f -u bind -4
14840 pts/0 S+ 0:00 grep --color=auto named
/etc/bind/named.conf.options (listen on any adress - DEMO!):
```plain
options {
directory "/var/cache/bind";
======================================================================$
// If BIND logs error messages about the root key being expired,
// you will need to update your keys. See https://www.isc.org/bind-keys
//======================================================================$
dnssec-validation auto;
auth-nxdomain no; # conform to RFC1035
listen-on { any; };
listen-on-v6 { any; };
};
```
DNS Zone in /etc/bind/named.conf.local:
```plain
zone "azure.intern" {
type master;
file "/etc/bind/zones/db.azure.intern"; # zone file path
};
```
Create Zone file:
sudo mkdir /etc/bind/zones
sudo cp /etc/bind/db.local /etc/bind/zones/db.azure.intern
sudo vim /etc/bind/zones/db.azure.intern
```plain
;
; BIND data file for local loopback interface
;
$TTL 604800
@ IN SOA ns1.azure.intern. admin.azure.intern. (
3 ; Serial
604800 ; Refresh
86400 ; Retry
2419200 ; Expire
604800 ) ; Negative Cache TTL
;
@ IN NS ns1.azure.intern.
@ IN A 127.0.0.1
@ IN AAAA ::1
ns1.azure.intern. IN A 192.168.0.4
myhost.azure.intern. IN A 40.112.72.205
```
Restart bind
sudo systemctl restart bind9
Check on dns server machine (redirect to localhost! Should throw no error.):
nslookup myhost.azure.intern localhost
VNET --> Add custom DNS server
Restart VM
sudo shutdown -r now
Create a test-client (optional)
- new VM
- new VNET: 192.168.1.0/24
- VNET Peering
- add Custom DNS server (private IP of DNS server, here: 192.168.0.4)
SSH into machine:
```shell
$ nslookup myhost.azure.intern
Server: 127.0.0.53
Address: 127.0.0.53#53
Non-authoritative answer:
Name: myhost.azure.intern
Address: 40.112.72.205
```
## How to setup CoreDNS in AKS
Add AKS cluster:
Install with Azure CNI!
Peer newly created VNET with DNS-VNET and ensure "Peering status" == "Connected"
Negative test (run a pod and lookup myhost.azure.intern - should fail!):
```shell
kubectl run --rm -it busy --image busybox /bin/sh
nslookup myhost.azure.intern
Server: 10.0.0.10
Address: 10.0.0.10:53
** server can't find myhost.azure.intern: NXDOMAIN
```
Add CoreDNS custom data:
```bash
cat << EOF | kubectl apply -f -
apiVersion: v1
kind: ConfigMap
metadata:
name: coredns-custom
namespace: kube-system
data:
azure.intern.server: |
azure.intern:53 {
errors
cache 30
forward . 192.168.0.4 # 'on-prem' DNS server
}
EOF
```
Restart DNS Pods:
kubectl delete pod --namespace kube-system --selector k8s-app=kube-dns
Positive test:
```shell
kubectl run --rm -it busy --image busybox /bin/sh
$ nslookup myhost.azure.intern
Server: 10.0.0.10
Address: 10.0.0.10:53
Name: myhost.azure.intern
Address: 40.112.72.205
# any other DNS lookups should also work:
$ nslookup microsoft.com
Server: 10.0.0.10
Address: 10.0.0.10:53
Non-authoritative answer:
Name: microsoft.com
Address: 40.76.4.15
Name: microsoft.com
Address: 40.112.72.205
Name: microsoft.com
Address: 40.113.200.201
Name: microsoft.com
Address: 13.77.161.179
Name: microsoft.com
Address: 104.215.148.63
```