BGP Example

Policy definition:

# Create policy
set policy route-map setmet rule 2 action 'permit'
set policy route-map setmet rule 2 set as-path prepend '2 2 2'

# Apply policy to BGP
set protocols bgp system-as 1
set protocols bgp neighbor 203.0.113.2 address-family ipv4-unicast route-map import 'setmet'
set protocols bgp neighbor 203.0.113.2 address-family ipv4-unicast soft-reconfiguration 'inbound'

Using ‘soft-reconfiguration’ we get the policy update without bouncing the neighbor.

Routes learned before routing policy applied:

vyos@vos1:~$ show ip bgp
BGP table version is 0, local router ID is 192.168.56.101
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, R Removed
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 198.51.100.3/32   203.0.113.2           1             0 2 i  < Path

Total number of prefixes 1

Routes learned after routing policy applied:

vyos@vos1:~$ show ip bgp
BGP table version is 0, local router ID is 192.168.56.101
Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,
              r RIB-failure, S Stale, R Removed
Origin codes: i - IGP, e - EGP, ? - incomplete

   Network          Next Hop            Metric LocPrf Weight Path
*> 198.51.100.3/32   203.0.113.2           1             0 2 2 2 2 i

Total number of prefixes 1
vyos@vos1:~$

You now see the longer AS path.

Transparent Proxy

The following example will show how VyOS can be used to redirect web traffic to an external transparent proxy:

set policy route FILTER-WEB rule 1000 destination port 80
set policy route FILTER-WEB rule 1000 protocol tcp
set policy route FILTER-WEB rule 1000 set table 100

This creates a route policy called FILTER-WEB with one rule to set the routing table for matching traffic (TCP port 80) to table ID 100 instead of the default routing table.

To create routing table 100 and add a new default gateway to be used by traffic matching our route policy:

set protocols static table 100 route 0.0.0.0/0 next-hop 10.255.0.2

This can be confirmed using the show ip route table 100 operational command.

Finally, to apply the policy route to ingress traffic on our LAN interface, we use:

set policy route FILTER-WEB interface eth1

Multiple Uplinks

VyOS Policy-Based Routing (PBR) works by matching source IP address ranges and forwarding the traffic using different routing tables.

Routing tables that will be used in this example are:

• table 10 Routing table used for VLAN 10 (192.168.188.0/24)

• table 11 Routing table used for VLAN 11 (192.168.189.0/24)

• main Routing table used by VyOS and other interfaces not participating in PBR

Policy-Based Routing with multiple ISP uplinks (source ./draw.io/pbr_example_1.drawio)

Add default routes for routing table 10 and table 11

set protocols static table 10 route 0.0.0.0/0 next-hop 192.0.1.1
set protocols static table 11 route 0.0.0.0/0 next-hop 192.0.2.2

Add policy route matching VLAN source addresses

set policy route PBR rule 20 set table '10'
set policy route PBR rule 20 description 'Route VLAN10 traffic to table 10'
set policy route PBR rule 20 source address '192.168.188.0/24'

set policy route PBR rule 30 set table '11'
set policy route PBR rule 30 description 'Route VLAN11 traffic to table 11'
set policy route PBR rule 30 source address '192.168.189.0/24'

Apply routing policy to inbound direction of out VLAN interfaces

set policy route 'PBR' interface eth0.10
set policy route 'PBR' interface eth0.11

OPTIONAL: Exclude Inter-VLAN traffic (between VLAN10 and VLAN11) from PBR

set firewall group network-group VLANS-GR description 'VLANs networks'
set firewall group network-group VLANS-GR network '192.168.188.0/24'
set firewall group network-group VLANS-GR network '192.168.189.0/24'

set policy route PBR rule 10 description 'VLAN10 <-> VLAN11 shortcut'
set policy route PBR rule 10 destination group network-group 'VLANS-GR'
set policy route PBR rule 10 set table 'main'

These commands allow the VLAN10 and VLAN11 hosts to communicate with each other using the main routing table.

Local route

The following example allows VyOS to use PBR for traffic, which originated from the router itself. That solution for multiple ISP’s and VyOS router will respond from the same interface that the packet was received. Also, it used, if we want that one VPN tunnel to be through one provider, and the second through another.

• 203.0.113.254 IP addreess on VyOS eth1 from ISP1

• 192.168.2.254 IP addreess on VyOS eth2 from ISP2

• table 10 Routing table used for ISP1

• table 11 Routing table used for ISP2

set policy local-route rule 101 set table '10'
set policy local-route rule 101 source '203.0.113.254'
set policy local-route rule 102 set table '11'
set policy local-route rule 102 source '192.0.2.254'
set protocols static table 10 route 0.0.0.0/0 next-hop '203.0.113.1'
set protocols static table 11 route 0.0.0.0/0 next-hop '192.0.2.2'

Add multiple source IP in one rule with same priority

set policy local-route rule 101 set table '10'
set policy local-route rule 101 source '203.0.113.254'
set policy local-route rule 101 source '203.0.113.253'
set policy local-route rule 101 source '198.51.100.0/24'

Clamp MSS for a specific IP

This example shows how to target an MSS clamp (in our example to 1360 bytes) to a specific destination IP.

set policy route IP-MSS-CLAMP rule 10 description 'Clamp TCP session MSS to 1360 for 198.51.100.30'
set policy route IP-MSS-CLAMP rule 10 destination address '198.51.100.30/32'
set policy route IP-MSS-CLAMP rule 10 protocol 'tcp'
set policy route IP-MSS-CLAMP rule 10 set tcp-mss '1360'
set policy route IP-MSS-CLAMP rule 10 tcp flags 'SYN'

To apply this policy to the correct interface, configure it on the interface the inbound local host will send through to reach our destined target host (in our example eth1).

set policy route IP-MSS-CLAMP interface eth1

You can view that the policy is being correctly (or incorrectly) utilised with the following command:

show policy route statistics