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If you have followed sequentially previous SOHO articles, you should have now a strong vanilla base in order to develop you home office network or you home network. 

Requirement

  • Basic Linux/Unix knowledge
  • Service provider networking knowledge

Overview

In the previous article we enabled and checked IPv4 connectivity between RARE/freeRouter and ISP box using sdn1 interface within 192.168.0.0/24 network. But as stated in the previous post, I'd like:

  • all people connected within 192.168.128.0/17
  • to access the external world

Article objective

In this article we will pursue the SOHO network appliance installation and enable IPv4 connectivity for all host connected within your internal network to the external world.

Diagrams

[ #004 ] - Do you need translation ? 

 Create router loopback in VRF inet

First step, let's create an interface Loopback0 within 192.168.128.0/17, let's say 192.168.254.1/32

SOHO router in VRF inet
sh run loopback0                                                        
interface loopback0
 no description
 vrf forwarding inet
 ipv4 address 192.168.254.1 255.255.255.255
 no shutdown
 no log-link-change
 exit
!
 Problem observation

First step, let's try to ping 8.8.8.8

ping 8.8.8.8
ping 8.8.8.8 /vrf inet /interface lo0                                  
pinging 8.8.8.8, src=192.168.254.1, vrf=inet, cnt=5, len=64, tim=1000, ttl=255, tos=0, sweep=false
.....
result=0%, recv/sent/lost=0/5/5, rtt min/avg/max/total=10000/0/0/5003

Hey ! It seems that it's not working as expected ! At the present time, it seems that no one is able to reach outside world. Let's try to figure out why.

Note

  • It is a common best practice to dedicate a loopback to a router in a VRF
  • Loopback are mostly used to identify a service proposed by the router
  • Each services are bound to this Loopback in a specific VRF 
 First troubleshooting action
traceroute 8.8.8.8 using looback0 as source address
traceroute 8.8.8.8 /vrf inet /interface lo0                            
tracing 8.8.8.8, src=192.168.254.1, vrf=inet, prt=0/33440, tim=1000, tos=0, len=64
1 192.168.254.1 time=0
2 null time=1000
3 null time=1000
4 null time=1000
5 null time=1000
6 null time=1000
7 null time=1000
8 null time=1000
9 null time=1000
10 null time=1000

This confirms the ping failures we observed previously. The output above indicate the packet does not even egress our SOHO router.

What is the inet VRF says ?

routes inside VRF inet
show ipv4 route inet                                                   
typ  prefix            metric  iface      hop            time
C    192.168.0.0/24    0/0     sdn1       null           14:30:07
LOC  192.168.0.90/32   0/1     sdn1       null           14:30:07
C    192.168.128.0/24  0/0     sdn999     null           14:30:13
LOC  192.168.128.1/32  0/1     sdn999     null           14:30:13
C    192.168.254.1/32  0/0     loopback0  null           14:30:15

So we have no default routes . Let's configure one then pointing towards ISP BOX gateway:

Default route configuration
conf t
ipv4 route inet 0.0.0.0 0.0.0.0 192.168.0.254
routes inside VRF inet
show ipv4 route inet                                                   
typ  prefix            metric  iface      hop            time
S    0.0.0.0/0         1/0     sdn1       192.168.0.254  14:30:07
C    192.168.0.0/24    0/0     sdn1       null           14:30:07
LOC  192.168.0.90/32   0/1     sdn1       null           14:30:07
C    192.168.128.0/24  0/0     sdn999     null           14:30:13
LOC  192.168.128.1/32  0/1     sdn999     null           14:30:13
C    192.168.254.1/32  0/0     loopback0  null           14:30:15

So at that point, packet send to 8.8.8.8 are sent to nexthop 192.168.0.254 via sdn1.

ping 8.8.8.8
ping 8.8.8.8 /vrf inet /interface lo0                                  
pinging 8.8.8.8, src=192.168.254.1, vrf=inet, cnt=5, len=64, tim=1000, ttl=255, tos=0, sweep=false
.....
result=0%, recv/sent/lost=0/5/5, rtt min/avg/max/total=10000/0/0/5003

But ping is still not not working. Let's figure out what's going on here.

 Networking environment assumption

As depicted in previous article:

  • ISP box has a demarcation point set to 192.168.0.254
  • So ISP box at some point is configured to perform Network Address Translation from 192.168.0.0/24 → ISP public IPv4 interface
  • When ISP box receives a ICMP ping from 192.168.254.1 which does not match any ISP box NAT rules → Packet is discarded

Therefore in order to have a working seamless networking environment from the ISP box point of view, traffic coming from 192.168.128.0/17 might need to be NAT(ed) into 192.168.0.0/24 network. Let's see If our guess is right.

 NAT to the rescue

Let's configure IPv4 Network Address Translation specifically for Loopback0

ping 8.8.8.8
!
conf t
access-list ACL-NAT4   
 sequence 10 deny all 192.168.128.0 255.255.128.0 all 192.168.128.0 255.255.128.0 all
 sequence 20 deny all any all 224.0.0.0 240.0.0.0 all                                          
 permit all 192.168.254.1 255.255.255.255 all any all     
exit
!
ipv4 nat inet sequence 10 srclist ACL-NAT4 interface sdn1
!

 In the config stanza above we configure an access-list called ACL-NAT4 in VRF inet that would translate all incoming packet matching 192.168.254.1 going to anywhere to interface sdn1 IPv4. But we also don't NAT for inter-vlan traffic within 192.168.128.0/17 and also does not touch multicast traffic.

ping 8.8.8.8
ping 8.8.8.8 /vrf inet /interface sdn1                                 
pinging 8.8.8.8, src=192.168.0.90, 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

Yahhoooo ! It works ... Our guess was good after all... (smile)

 Final NAT configuration and subnetting assumptions

For the future we assume that the home network is subnetted as follow and are all inside VRF inet:

  • appliance port#1 @ sdn1: 192.168.0.0/24 (ISP subnet)
  • appliance port#2 @ sdn2: 192.168.130.0/24
  • appliance port#3 @ sdn3: 192.168.133.0/24
  • appliance port#4 @ sdn4: 192.168.134.0/24 (unused)
  • appliance port#5 @ sdn5: 192.168.135.0/24
  • appliance port#6 @ sdn6: 192.168.136.0/24
  • appliance integrated wifi @ sdn998: 192.168.129.0/24
  • appliance loopback inet @ loopback0: 192.168.129.0/24


ping 8.8.8.8
!
conf t
access-list ACL-NAT4
 sequence 10 deny all 192.168.128.0 255.255.128.0 all 192.168.128.0 255.255.128.0 all
 sequence 20 deny all any all 224.0.0.0 240.0.0.0 all
 sequence 30 permit all 192.168.128.0 255.255.255.0 all any all
 sequence 40 permit all 192.168.129.0 255.255.255.0 all any all
 sequence 50 permit all 192.168.130.0 255.255.255.0 all any all
 sequence 60 permit all 192.168.133.0 255.255.255.0 all any all
 sequence 70 permit all 192.168.135.0 255.255.255.0 all any all
 sequence 80 permit all 192.168.136.0 255.255.255.0 all any all
 sequence 90 permit all 192.168.254.1 255.255.255.255 all any all
 exit
!
ipv4 nat inet sequence 10 srclist ACL-NAT4 interface sdn1
!

 In the config stanza above we configure an access-list called ACL-NAT4 in VRF inet that would translate all incoming packet matching 192.168.[128|129|130|133|135|136|254].0/24 going to anywhere.

Note

Each time you modify ACL-NAT4 you will need to re-apply the NAT calls:

ping 8.8.8.8
!
conf t
! modify access-list ACL-NAT4
!
no ipv4 nat inet sequence 10 srclist ACL-NAT4 interface sdn1
ipv4 nat inet sequence 10 srclist ACL-NAT4 interface sdn1
!

Also notice that we are NAT(ing), 192.168.128.0/24 which is the OOBM subnet of the Linux appliance itself. This is needed during Debian system update/upgrade operation and also needed during the auto-upgrade feature that I'll describe in a next article.

IPv6 does need NAT in my specific case as my ISP has allocated me public IPv6 prefixes. We will see IPv6 configuration in the next articles.

Verification

 Available NAT command verification
NAT show commands
!
show ipv4 nat ?                                                        
  <vrf> - name of routing table
!
show ipv4 nat inet ?                                                   
  statistics   - list of configuration entries
  translations - list of translation entries
!
 Trigger NAT traffic translation
ping 8.8.8.8 in order to trigger NAT translation
ping 8.8.8.8 /vrf inet /interface lo0                                 
pinging 8.8.8.8, src=192.168.254.1, 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=2/3/4/16
 Check NAT translation
NAT translation verification
mjolnir#show ipv4 nat inet translations | i 192.168.254.1                      
1      8.8.8.8 4392          192.168.0.90 4392      8.8.8.8 4392          192.168.254.1 4392     00:00:01  00:00:01  00:05:00  1        64
1      192.168.254.1 4392    8.8.8.8 4392           192.168.0.90 4392     8.8.8.8 4392           00:00:01  00:00:01  00:05:00  1        64
1      8.8.8.8 4393          192.168.0.90 4393      8.8.8.8 4393          192.168.254.1 4393     00:00:01  00:00:01  00:05:00  1        64
1      192.168.254.1 4393    8.8.8.8 4393           192.168.0.90 4393     8.8.8.8 4393           00:00:01  00:00:01  00:05:00  1        64
1      8.8.8.8 4394          192.168.0.90 4394      8.8.8.8 4394          192.168.254.1 4394     00:00:01  00:00:01  00:05:00  1        64
1      192.168.254.1 4394    8.8.8.8 4394           192.168.0.90 4394     8.8.8.8 4394           00:00:01  00:00:01  00:05:00  1        64
1      8.8.8.8 4395          192.168.0.90 4395      8.8.8.8 4395          192.168.254.1 4395     00:00:01  00:00:01  00:05:00  1        64
1      192.168.254.1 4395    8.8.8.8 4395           192.168.0.90 4395     8.8.8.8 4395           00:00:01  00:00:01  00:05:00  1        64
1      8.8.8.8 4396          192.168.0.90 4396      8.8.8.8 4396          192.168.254.1 4396     00:00:01  00:00:01  00:05:00  1        64
1      192.168.254.1 4396    8.8.8.8 4396           192.168.0.90 4396     8.8.8.8 4396           00:00:01  00:00:01  00:05:00  1        64

Conclusion

In this article

  • We finally have a router that enables connectivity for all hosts inside the home network to the outside world
  • due to the ISP specific setup, our router had to translate inner home IP subnets to subnet that can be in turn NAT'ed by the ISP box.
  • We have a consistent IPv4 addressing plan 
  • We now can add very exciting feature from now on. (In next articles !)


RARE validated design: [ SOHO #004 ] - key take-away

In this example we are proposing a basic connectivity scenario. However, keep in mind that depending on your location the configuration might be drastically different. But do not fear ! RARE/freeRouter has all the features need to enable connectivity !

  • NAT64 is available. So in case you want to run a pure IPv6 network, freeRouter can NAT64 traffic for you.
  • NAT46 is also available. In case you are desperate and don't want to implement a pure IPv6 home network and have an ISP running only IPv6, freeRouter can NAT46 your traffic for you !
  • In the example described, we are lucky to have IPv6 public global IPv6 address. We will see IPv6 configuration in subsequent articles.
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