In this Tutorial We will be discussing how to setup an External Border Gateway Protocol (EBGP) between two routers.

Prerequisites

To complete this tutorial, you will need:

A laptop running Linux or MacOS. for this tutorial I will be using a laptop running Ubuntu 16
A console cable. Since all the new laptops today don't come with a USB port, you will need a USB to Console adapter
The program "Screen"

If you don't have "screen" install it with the command below

sudo apt-get install screen

The Goal

File:Bgp1.png

Our goal is to setup the network like in the above image.

We have 2 offices. One in Texas and the other one in San Fransisco. Both offices have a Juniper MX80 router. The Texas router cr1-tx is in AS 17 and the San Fransico router cr1-sfo is in AS 29. We need to setup an External Border Gateway Protocol (EBGP) to connect both offices. If we were to connect 2 router in the same AS, we was going to use an IBGP (Internal Border Gateway Protocol) such as OSPF. We will discuss about this in another tutorial.

Router Setup

We are going to perform the basic setup of the router like we did for the switches in [[JunOS Basics[1]]

The process is the same. Please refer to the link above

Access the router
Setup the root password
Setup the device name
Create a privilege user
setup Management interface and enable SSH

Note: for the management setup, since we are using a router the management interface on the MX80 is not me0 like on the switch. The management interface is fxp0. See below for the how the management interface is setup.

root@cr1-tx# show interfaces 
fxp0 {
    description mgmt;
    unit 0 {
        family inet {
            address 10.192.0.103/24;
        }
    }
}

After setting up all the basic on both routers, it is time to process to the EBGP setup.

EBGP Setup

On cr1-tx

We are going to use the interface xe-0/0/0 which is a 10Gbs interfaces.

Step 1: Set interface description

set interfaces xe-0/0/0 description to-cr1-sfo

Check before committing

root@cr1-tx# show | compare                                        
[edit interfaces]
+   xe-0/0/0 {
+       description to-cr1-sfo;
+   }

Step 2: Assign an IP address to the interface

set interfaces xe-0/0/0 unit 0 family inet address 10.10.10.1/30

Check before committing

root@cr1-tx# show | compare 
[edit interfaces xe-0/0/0]
+    unit 0 {
+        family inet {
+            address 10.10.10.1/30;
+        }
+    }

Step 3: Set the Autonomous system (AS) number To set the AS number we need to be in the routing-options level for that type in

edit routing-options

[edit routing-options]
root@cr1-tx# set autonomous-system 17

step 4 : Create the BGP group/ add external neighbor address

To do this we need to be in the protocols bgp group external-peers level

Type "exit" to leave the routing-options level and then type in

[edit]
root@cr1-tx# edit protocols bgp group external-peers

[edit protocols bgp group external-peers]
root@cr1-tx# set neighbor 10.10.10.2

Step 5: Specify external AS number

[edit protocols bgp group external-peers]
root@cr1-tx# set peer-as 29

Step 6: Set the peer type

[edit protocols bgp group external-peers]
root@cr1-tx# set type external

Type " exit"

Checking

[edit]
root@cr1-tx# show interfaces 
xe-0/0/0 {
    description to-cr1-sfo;
    unit 0 {
        family inet {
            address 10.10.10.1/30;
        }
    }
}

[edit]
root@cr1-tx# show protocols 
bgp {
    group external-peers {
        type external;
        peer-as 29;
        neighbor 10.10.10.2;
    }
}

[edit]
root@cr1-tx# show routing-options 
autonomous-system 17;

If everything looks good, you can commit

Verification

In operation mode,do show run neighbor

root@cr1-tx> show bgp neighbor 
Peer: 10.10.10.2 AS 29         Local: unspecified AS 17   
  Type: External    State: Idle           Flags: <PeerInterfaceError>
  Last State: NoState       Last Event: NoEvent
  Last Error: None
  Options: <Preference PeerAS Refresh>
  Holdtime: 90 Preference: 170
  Number of flaps: 0

We can see from the output the Local= unspecified and the state is Idle Last State: NoState Last Event: NoEvent. The reason being that we haven't setup cr1-sfo yet.

On cr1-sfo

JunOS BGP

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