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.. include:: ../_include/need_improvement.txt
######
Policy
######
Routing Policies could be used to tell the router (self or neighbors) what
routes and their attributes needs to be put into the routing table.
There could be a wide range of routing policies. Some examples are below:
* Set some metric to routes learned from a particular neighbor
* Set some attributes (like AS PATH or Community value) to advertised routes to neighbors
* Prefer a specific routing protocol routes over another routing protocol running on the same router
Example
=======
**Policy definition:**
.. code-block:: none
# 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 1 neighbor 203.0.113.2 address-family ipv4-unicast route-map import 'setmet'
set protocols bgp 1 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:**
.. code-block:: none
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:**
.. code-block:: none
vyos@vos1:~$ sho ip b
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.
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