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So everyone inside home network can reach the Internet thanks to NAT translation described in SOHO #004

Requirement

  • Basic Linux/Unix knowledge
  • Service provider networking knowledge

Overview

In the previous article we enabled and checked IPv4 connectivity between all potential host within 192.168.128.0/17 and the outside Networks beyond ISP box. But, this is pretty useless as I can't imagine my kids typing IPv6 address (2001:8b0:0:30::666:102) in the browser in order to play a FUN puzzle. (Though for now we are suppose to have only IPv4 (smile)) So we definitely need to provide name service resolution at the SOHO router itself.

Article objective

In this article we will pursue the SOHO network appliance installation and enable name service to all host @ home.

Diagrams

[ SOHO #005 ] - "Got your Id number, but ... What's your name ?"

 Configure SOHO router as DNS client to an existing DNS server

First step, it is need to configure the router as a client name for an existing DNS server.

SOHO router in VRF inet
!
conf t
client name-server 8.8.8.8 1.1.1.1 
!

So this declare our SOHO router as DNS client for 8.8.8.8 as primary DNS server and 1.1.1.1 as backup DNS server.

 Set VRF for locally originated traffic from the SOHO router

This step is mandatory as it will bind traffic originated from SOHO router to a specific VRF (here: inet). So this can be also qualified as "VRF proxy-awareness". In this way all DNS traffic originated from the router will be bound to VRF inet. This is done in 2 steps. The first step is to create the proxy-profile and bind it to the main VRF inet. The second step is to declare the SOHO router as client of this proxy-profile service.

SOHO router in VRF inet
!
! step 1
!
proxy-profile pp-inet
 vrf inet
 exit
!
! step 2
!
client proxy pp-inet
!
 Setting UP DNS cache acting as DNS server for all host @ home network

Step -3-, configure DNS cache / server 

  • enable recursion (recursive query toward other DNS defined 8.8.8.8, 1.1.1.1)
  • bind it to a specific interface (so SOHO router will answer only DNS from this interface)
  • bind it to VRF inet
SOHO router DNS cache
!
server dns ns-inet
 recursion enable
 interface loopback0
 vrf inet
 exit
!

So this declare our SOHO router as DNS client for 8.8.8.8 as primary DNS server and 1.1.1.1 as backup DNS server

 Configure DNS into DHCP to propogate default "local" zone

Step -4-, configure DNS and DHCP to propagate default dummy zone local

  • Use local if you don't plan to propagate a domain name
  • create local as dummy zone


Propagate "local" zone
!
server dhcp4 dh4-inet
 dns-server 192.168.254.1
 domain-name local
 exit
!
server dns ns-inet
 zone local
 exit
!

Verification

 step -1- and step -2- outcomes

When -1- and -2- are realised the router can resolve name

DNS resolution from CLI (DNS query originated by router)
ping www.free.fr /vrf inet                                             
pinging 212.27.48.10, src=null, vrf=inet, cnt=5, len=64, tim=1000, ttl=255, tos=0, sweep=false
!!!!!
result=100%, recv/sent/lost=5/5/0, rtt min/avg/max/total=3/3/4/16
 step -3- and step -4- outcomes

This can be verified only using a host connected to SOHO router. Let's assume a laptop connected behind sdn6.

ping & ping6 hostname
...
╭─[10/31/20|3:01:19]loui@MacBook-Pro-de-Frederic.local ~  
╰─➤  ping www.free.fr
PING www.free.fr (212.27.48.10): 56 data bytes
64 bytes from 212.27.48.10: icmp_seq=0 ttl=57 time=3.670 ms
64 bytes from 212.27.48.10: icmp_seq=1 ttl=57 time=6.666 ms
64 bytes from 212.27.48.10: icmp_seq=2 ttl=57 time=6.163 ms
64 bytes from 212.27.48.10: icmp_seq=3 ttl=57 time=6.118 ms
^C
--- www.free.fr ping statistics ---
4 packets transmitted, 4 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 3.670/5.654/6.666/1.166 ms
╭─[10/31/20|3:40:12]loui@MacBook-Pro-de-Frederic.local ~  
╰─➤  ping6 www.free.fr
PING6(56=40+8+8 bytes) 2a01:e0a:159:2857:b9d9:e9e0:ae30:88e5 --> 2a01:e0c:1::1
16 bytes from 2a01:e0c:1::1, icmp_seq=0 hlim=56 time=3.805 ms
16 bytes from 2a01:e0c:1::1, icmp_seq=1 hlim=56 time=6.898 ms
16 bytes from 2a01:e0c:1::1, icmp_seq=2 hlim=56 time=5.868 ms
16 bytes from 2a01:e0c:1::1, icmp_seq=3 hlim=56 time=5.729 ms
^C
--- www.free.fr ping6 statistics ---
4 packets transmitted, 4 packets received, 0.0% packet loss
round-trip min/avg/max/std-dev = 3.805/5.575/6.898/1.117 ms

...

IPv4 / IPv6 name resolution
...
╭─[10/31/20|3:42:11]loui@MacBook-Pro-de-Frederic.local ~  
╰─➤  dig www.free.fr                                                                                                                                                127 ↵

; <<>> DiG 9.10.6 <<>> www.free.fr
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 25030
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;www.free.fr.                   IN      A

;; ANSWER SECTION:
www.free.fr.            20961   IN      A       212.27.48.10

;; Query time: 21 msec
;; SERVER: 192.168.254.1#53(192.168.254.1)
;; WHEN: Sat Oct 31 15:42:18 CET 2020
;; MSG SIZE  rcvd: 56

╭─[10/31/20|3:42:18]loui@MacBook-Pro-de-Frederic.local ~  
╰─➤  dig AAAA www.free.fr  

; <<>> DiG 9.10.6 <<>> AAAA www.free.fr
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 21770
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;www.free.fr.                   IN      AAAA

;; ANSWER SECTION:
www.free.fr.            21075   IN      AAAA    2a01:e0c:1::1

;; Query time: 5 msec
;; SERVER: 192.168.254.1#53(192.168.254.1)
;; WHEN: Sat Oct 31 15:42:29 CET 2020
;; MSG SIZE  rcvd: 68
...

As said IPv6 verification are just FYI, as we are supposed to have deployed only IPv4 till now. The point to show off IPv6 verification is to verify DNS AAAA request are working properly.

Conclusion

In this article DNS service has been enabled at:

  • SOHO router level 
  • All host getting an IPv4 via DHCP will get a DNS server set to SOHO@loopback0 (192.168.254.1)

RARE validated design: [ SOHO #005 ] - key take-away

In this example the key take-away are:

  • proxy-profile usage in order to proxy DNS query into VRF inet
  • proxy-profile can be used to proxy other types of traffic
  • data/routed traffic is not affected by proxy-profile



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