routing policies

Question 1

what are the default import/export policies for BGP?

Answer 1

Accept all v4 in and import into inet.0

readvertise all active BGP routes to BGP speakers.

Question 2

What are the default import/export policies for OSPF?

Answer 2

accept all OSPf routes into inet.0

reject all exports (OSPF LSDB is fully synced)

Question 3

What are the default import/export policies for ISIS?

Answer 3

accept all routes into inet.0

reject all exports (LSDB is fully synced…)

Question 4

what are the default routing policies for RIP?

Answer 4

accept all in to inet.0

reject all exports, including RIP routes

Question 5

How do you export RIP routes?

Answer 5

add a policy;

edit policy-options policy-statement <policy>
set term <term> from protocol <protocol>
set term <term> then accept</term></protocol></term></policy>

you then create a RIP group;

edit protocols rip
set group my-rip-group export <policy> neighbor <neighbor>
set group my-rip-group export <policy> neighbor <neighbor>
set group my-rip-group export <policy> neighbor <neighbor></neighbor></policy></neighbor></policy></neighbor></policy>

Question 6

What are the building blocks of route policies?

Answer 6

terms.
You give each term a name.
They are if-then statements. If a term doesnt match it moves on to the next one.

Question 7

What are the route policy terminating actions?

Answer 7

accept
reject

Question 8

how can you add new terms in the middle of a policy?

Answer 8

via CLI using the Insert command

Question 9

What can you match a route policy with using a from statement?

Answer 9

prefix - route-filter or prefix-list
protocol (ospf, bgp etc)
routing attributes - area ID, as path, community
next hop
Neighbour

If no from statement is used it matches everything

Question 10

Whats the difference between prefix lists in JUNOS?

Answer 10

Prefix lists only contain the prefix.

You can apply a “prefix-list-filter” to a prefix list and specific exact, longer, orlonger matching when you apply it to a route policy.

Question 11

Whats a route-filter in a route policy?

Answer 11

its just a prefix direct in the policy, and then the same exact longer orlonger matching types are possible

Question 12

In a route policy, Whats the prefix-length match type?

Answer 12

Matches prefixes within a given prefix length range. match is INCLUSIVE.

Question 13

whats the gotcha with maxing route-filters?

Answer 13

it evaluates most to least specific, and will ONLY lookup against the first one the prefix matches against. Longest match routing(!)

Question 14

Route policy actions. What are they?

Answer 14

Terminating:

Accept
Reject

Flow Control:

Next term
Next Policy

Modification attributes:
Community (add, delete, set)
preference
as-path prepend
next-hop

Question 15

How do you implement route policy?

Answer 15

1. Define the policy under edit policy-options
2. Apply the policy within the protocol configuration;
   eg edit protocols ospf or edit protocols bgp

Some protocols like BGP you apply policy within an address family, or a neighbor, others its process level. ISIS is process level as LSDB is synced

import/export policies will use the one configured at the lowest hierarchy only. EG: if you have a permit at BGP group level and a deny at neighbor level, its getting denied.

Question 16

How do you chain policies?

Answer 16

You can chain together multiple policies. It then goes left to right, top to bottom (ie, if policy 1 doesnt match the route it checks policy 2, etc)

Question 17

When is the default policy used?

Answer 17

When all policies are looked at and no matching criteria are found.

Question 18

When redistributing into a routing protocol, which way around is import vs export?

Answer 18

You Export FROM the RIB into the proccess.

So to redistribute INTO ospf you use an EXPORT process.