BGP basic configuration using Juniper JUNOS routers

 In Juniper's Junos OS, the configuration is more hierarchical and modular than Cisco's IOS. Instead of placing all commands under a single process, you typically define BGP under the protocols hierarchy.

Here is an example of a basic EBGP setup between two Juniper routers.

Network Topology

• Router 1 (AS 100): Interface ge-0/0/0.0 with IP 1.1.1.1/30

• Router 2 (AS 200): Interface ge-0/0/0.0 with IP 1.1.1.2/30

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1. Router 1 Configuration (AS 100)

In Junos, you must set the Autonomous System number under routing-options and then configure the BGP group.

Code snippet

[edit]
# Set the Local AS
set routing-options autonomous-system 100
# Create a BGP Group and Peer
set protocols bgp group EXTERNAL-PEERS type external
set protocols bgp group EXTERNAL-PEERS neighbor 1.1.1.2 peer-as 200
# Exporting a route (Junos requires a policy to advertise networks)
set policy-options policy-statement ADVERTISE-LOCAL term 1 from route-filter 10.10.10.0/24 exact
set policy-options policy-statement ADVERTISE-LOCAL term 1 then accept
set protocols bgp group EXTERNAL-PEERS export ADVERTISE-LOCAL

Note: Unlike Cisco, Juniper does not advertise anything by default. You must create an export policy to announce your routes to a BGP neighbor.

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2. Router 2 Configuration (AS 200)

Code snippet

[edit]
set routing-options autonomous-system 200
set protocols bgp group TO-R1 type external
set protocols bgp group TO-R1 neighbor 1.1.1.1 peer-as 100
# Optional: Add export policy here if R2 needs to advertise networks back.

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3. Comparison of Key Differences

Feature	Cisco IOS	Juniper Junos
AS Configuration	router bgp [AS]	set routing-options autonomous-system [AS]
Neighbor Setup	neighbor [IP] remote-as [AS]	set protocols bgp group [Name] neighbor [IP] peer-as [AS]
Advertising Routes	network [IP] mask [Mask]	Policy-based (export [Policy-Name])
Implicit Deny	Advertises nothing by default	Advertises nothing without an explicit Export Policy

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4. Verification Commands

To check the status of your BGP peers and the routes being exchanged in Junos:

• show bgp summary: Displays the state of the BGP neighbors. Look for the State column; "Established" means it is working.

• show bgp neighbor: Provides detailed information about a specific neighbor.

• show route protocol bgp: Shows all routes currently in the routing table that were learned via BGP.

• show route advertising-protocol bgp 1.1.1.2: Verifies exactly what routes you are sending to that specific neighbor.

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