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-0/0/0.0with IP1.1.1.1/30Router 2 (AS 200): Interface
ge-0/0/0.0with IP1.1.1.2/30
1. Router 1 Configuration (AS 100)
In Junos, you must set the Autonomous System number under routing-options and then configure the BGP group.
[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.
2. Router 2 Configuration (AS 200)
[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.
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 |
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 theStatecolumn; "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.
Checkout Juniper Network Simulator Juniper Netsim at certexams.com
