JunOS Routing Essentials

Route Preference

Routing Info Source	Default Preference
Direct	0
Local	0
Static	5
OSPF Internal	10
IS-IS Level 1 Internal	15
IS-IS Level 2 Internal	18
RIP	100
OSPF AS External	150
IS-IS Level 1 External	160
IS-IS Level 2 External	165
BGP	170

Lower numbers are preferred.

Equal-cost load balancing is done by randomly choosing among the equal paths.

Routing Instances

master routing instance is primary

An interface can only belong to one routing instance.

OSPF

Static Routes

discard is silent

Routing Policies

Import accepts routing updates, export sends out routing updates.

edit policy-options

Every protocol has a default policy

inet.0 Table
Protocol	Import Policy	Export Policy
BGP	accept bgp	accept active bgp
OSPF	accept ospf	reject -- floods by default *
IS-IS	accept is-is	reject -- floods by default *
RIP	accept rip from explicitly configured neighbors	reject everything
* Link-State Updates are sent and allowed by default; this only prevents routes from other protocols from being exported

Routing Policy

Export policy is used to export static route into OSPF.

Two steps: Define policy and apply policy.

Define policy under the edit policy-options hierarchy.

Apply routing policies as import or export policies at different levels (protocol dependent). For OSPF, only protocol-level import and export policies are allowed.

Policy example:

[edit policy-options]
user@router# show
policy-statement policy-1 {
    term reject-rfc1918-prefixes {
        from {
            route-filter 172.16.0.0/12 orlonger;
            route-filter 192.168.0.0/16 orlonger;
            route-filter 10.0.0.0/8 orlonger;
        }
        then reject;
    }
}

Routing Commands

show route protocol static

show route protocol ospf

show route forwarding-table

show route instance

set instance-type virtual-router

edit routing-options
To configure a static route

Extras--Not on Test

Each Routing instances has interfaces, a Zone, with a Routing Policy

Policy contains conditions.

Each condition has match criteria, THEN clause, and either ACCEPT or REJECT

Policy has a "Next Policy" pointer to then go to the next policy.

A policy's internal structure is the same as a firewall filter.

Both policies and firewall filters can have non-terminating actions, such as logging or changing class of service. Those actions can act as an IDS or an IPS.

Packet comes in.

First thing it hits is the POLICER.

Next it hits the FIREWALL FILTER.

Then it hits a DECISION POINT: Is there an EXISTING SESSION?

If not, it's the first packet in a session, and it goes through the FIRST PATH: SCREEN OS, SOURCE NAT, RT LOOKUP, POLICY, EGRESS PORT POLICY, DESTINATION NAT, APPLICATION LAYER GATEWAY, SESSION LOG CACHE.

If the first packet is dropped, all future packets in this session are denied.

All further packets in that session use the SESSION LOG CACHE to go down the FAST PATH.