Advanced configuration

The advanced configuration is implemented here. This configuration combines three simple configurations and also includes an iBGP link set parallel to the OSPF link.

The client’s network consists of the router R2, R3 and Stormshield Network firewall. The router R1 is an external BGP neighbor. This network represents a realistic architecture model, except for the fact that all the routers are physically connected by a single LAN.

We will implement a standard filter policy for:

  • announcing only public BGP networks to outside the network,
  • not spreading internal or Martian networks in the internal BGP,
  • tagging one of the learned routes en eBGP with a local-preference of 250. This measure is generally implemented to monitor load balancing between several eBGP neighbors,
  • announcing only one default route in OSPF,
  • announcing only one default route in RIP.

The networks announced by R2 and R3 are announced respectively via BGP and RIP. The use of OSPF to announce the default route is only for learning purposes.

BIRD configuration

Below is the equivalent configuration file in BIRD.

     
router id 192.168.97.219;
 
function is_locormartians()
 

prefix set martians;

  {
  martians = [ 169.254.0.0/16+, 172.16.0.0/12+, 192.168.0.0/16+,
10.0.0.0/8+, 224.0.0.0/4+, 240.0.0.0/4+ ];
  # default
  if net.ip = 0.0.0.0 then return true;
  # LIR not authorized
  if (net.len < 8) || (net.len > 24) then return true;
  # martians
  if net ~ martians then return true;
  # local
  if net = 100.100.100.100/32 then return true;
  return false;
}
 
filter out_eBGP {
  if net ~ [ 172.16.0.0/24, 3.3.3.3/32, 1.1.1.0/24 ]
  then accept;
  else reject;
}
 
filter out_iBGP {
  if ( is_locormartians() )
  then reject;
  else accept;
}
 
filter lp_tag_in {
  if net = 2.2.4.0/24 then {
 

bgp_local_pref = 250;

 

accept;

 

} else accept;

}
 
filter default_ok {
 

if net = 0.0.0.0/0 then {

 

accept;

 

} else reject;

}
 
protocol kernel {
  persist; # Don't remove routes on bird shutdown
  scan time 20;

# Scan kernel routing table every 20 seconds

  export all;

# Default is export none

  learn;

# Learn all alien routes from the kernel

  preference 254;

# Protect kernel routes with a high preference

  }  
 
protocol device {
  scan time 10;

# Scan interfaces every 10 seconds

}
 
protocol direct {
 

interface "em3";

}
 
protocol rip MyRIP {

# You can also use an explicit name

 

debug all;

 

interface "em4" { mode multicast; };

    mode multicast;
    authentication none;
    };
 

honor always;

 

authentication none;

 

import all;

 

export filter default_ok;

}
 
protocol ospf MyOSPF {
 

export filter default_ok;

 

import all;

 

area 0.0.0.0 {

 

stub no;

 

interface "em4" {

 

type broadcast;

    };
  };
}
protocol bgp router1 {
 

debug all;

 

description "My 1st BGP uplink";

 

local as 65065;

 

neighbor 100.100.100.100 as 65001;

 

multihop 5;

 

hold time 180;

 

keepalive time 60;

 

export filter out_eBGP;

 

import filter lp_tag_in;

 

source address 200.200.200.200;

}
protocol bgp router2 {
 

description "My local BGP neighbor";

 

local as 65065;

 

neighbor 192.168.97.102 as 65065;

 

keepalive time 60;

 

next hop self;

 

export filter out_iBGP;

 

import all;

}

 

NOTE
You are also advised to set the parameter "priority 0" in the interface section of the OSPF node configuration in order to disable the firewall's role in elections for Designated Router / Backup Designated Router roles.


Stormshield Network Firewall’s routing table

   
bird> show route
0.0.0.0/0 via 192.168.97.1 on em4 [kernel1 14:37:15] * (254)
100.100.100.100/32 via 192.168.97.101 on em4 [kernel1 14:37:15] * (254)
3.3.3.3/32 via 192.168.97.103 on em4 [MyRIP 14:37:06] * (120/2)
192.168.97.0/24 dev em4 [MyOSPF 14:01:33] * I (150/10) [192.168.97.102]
  via 192.168.97.102 on em4 [router2 14:01:17] (100/10) [i]
1.1.1.0/24 via 192.168.97.102 on em4 [MyOSPF 14:01:36] * E2 (150/10/10000) [192.168.97.102]
  via 192.168.97.102 on em4 [router2 14:01:17] (100/10) [i]
1.1.3.0/24 via 192.168.97.102 on em4 [MyOSPF 14:01:36] * E2 (150/10/10000) [192.168.97.102]
  via 192.168.97.102 on em4 [router2 14:01:17] (100/10) [i]
2.2.2.0/24 via 192.168.97.101 on em4 [router1 13:54:12 from 100.100.100.100] * (100/?) [AS65001i]
2.2.4.0/24 via 192.168.97.101 on em4 [router1 14:01:17 from 100.100.100.100] * (100/?) [AS65001i]
172.16.0.254/32 dev lo0 [kernel1 14:37:15] * (254)
192.168.97.219/32 dev lo0 [kernel1 14:37:15] * (254)
172.16.0.0/24 dev em3 [direct1 13:54:11] * (240)
10.200.45.254/32 dev lo0 [kernel1 14:37:15] * (254)
 

 

In order to check the local-preference on the router 2.2.4.0/24, the details of the routes for the instance of the protocol router1 will be displayed.


bird> show route protocol router1 all
2.2.2.0/24 via 192.168.97.101 on em4 [router1 13:54:12 from 100.100.100.100] * (100/?) [AS65001i]
Type: BGP unicast univ
BGP.origin: IGP
BGP.as_path: 65001
BGP.next_hop: 100.100.100.100
BGP.local_pref: 100

2.2.4.0/24 via 192.168.97.101 on em4 [router1 14:01:17 from 100.100.100.100] * (100/?) [AS65001i]
Type: BGP unicast univ
BGP.origin: IGP
BGP.as_path: 65001
BGP.next_hop: 100.100.100.100
BGP.local_pref: 250

 

Router R3 – show IP route

You will notice here that the default route is also announced.


@router3:~$ show ip route
Codes: K - kernel route, C - connected, S - static, R - RIP, O - OSPF,
I - ISIS, B - BGP, > - selected route, * - FIB route
R>* 0.0.0.0/0 [120/2] via 192.168.97.1, eth0, 00:06:15
C>* 1.1.8.0/24 is directly connected, lo
C>* 1.1.9.0/24 is directly connected, lo
S>* 3.3.3.3/32 [1/0] is directly connected, Null0, bh
C>* 127.0.0.0/8 is directly connected, lo
C>* 192.168.97.0/24 is directly connected, eth0
@router3:~$

 

In the event this traffic has to be routed symmetrically - for example when there is NAT – the BIRD configuration has to be adapted in order to announce the firewall as the next hop. The changes can be made in the filter “default_ok” which is used for announcing the default route to R3 via RIP and to R2 via OSPF:

  
filter default_ok
{
  if net = 0.0.0.0/0 then
  {
  dest = RTD_UNREACHABLE; # annonce le firewall comme next-hop pour cette route
  accept;
  }
}
 

 

To impose a gateway other than the firewall itself, you will need to use the directive:


gw = <ip>;

 

Router R2 – show IP route


@router2:~$ show ip route
Codes: K - kernel route, C - connected, S - static, R - RIP, O - OSPF,
I - ISIS, B - BGP, > - selected route, * - FIB route
O>* 0.0.0.0/0 [110/10000] via 192.168.97.1, eth0, 22:26:17
C>* 1.1.1.0/24 is directly connected, lo
C>* 1.1.3.0/24 is directly connected, lo
B>* 2.2.2.0/24 [200/1] via 100.100.100.100 (recursive via 192.168.97.1), 00:02:04
B>* 2.2.4.0/24 [200/1] via 100.100.100.100 (recursive via 192.168.97.1), 00:02:04
C>* 127.0.0.0/8 is directly connected, lo
C>* 192.168.97.0/24 is directly connected, eth0
@router2:~$

 

Router R1 – show IP route


@router1:~$ show ip route
Codes: K - kernel route, C - connected, S - static, R - RIP, O - OSPF,
I - ISIS, B - BGP, > - selected route, * - FIB route
S>* 0.0.0.0/0 [1/0] via 192.168.97.1, eth0
B>* 1.1.1.0/24 [20/0] via 200.200.200.200 (recursive via 192.168.97.219), 00:00:29
C>* 2.2.2.0/24 is directly connected, lo
C>* 2.2.4.0/24 is directly connected, lo
B>* 3.3.3.3/32 [20/0] via 200.200.200.200 (recursive via 192.168.97.219), 00:00:08
C>* 100.100.100.100/32 is directly connected, lo
C>* 127.0.0.0/8 is directly connected, lo
B>* 172.16.0.0/24 [20/0] via 200.200.200.200 (recursive via 192.168.97.219), 00:00:29
C>* 192.168.97.0/24 is directly connected, eth0
S>* 200.200.200.200/32 [1/0] via 192.168.97.219, eth0
@router1:~$