Category Archives: Juniper

Github Link – JunOS Automation

Hi All

Please see my Github link for Junos-automation examples which should be very handy in your environment i.e production and testing/integration. Let me know if there are any particular examples you would like me to share with you.

GitHub Link



Juniper Config Backup on GITLAB

Hi All

In this blog, we will see how we can take the backup of router configs and push it to gitlab for version control.

We will take Juniper routers here for example and build the script in Python and run our task as a cronjob on CentOS 7 to automatically backup the configs onto GITLAB.
We will use power of Git here to store the differentials in configs and we can see the differences in Gitlab UI.

So let’s see how we can achieve it.
Before starting with config backup, let’s build the device store on which we will be running the script or in other words backup will be running. For this we are storing the values in YAML file as dictionary. You can either store the values as list or Dictionary in YAML. You can use json also to store the same data instead of YAML.

Yaml file (.yml)
# Add devices here in form Hostname: 'ip address'
  Manchester_MX10003: ''
  Glasgow_MX10003: ''
  London_MX104: ''
  Leeds_MX104: ''
  Bristol_MX104: ''

Above are the file contents, where we are storing the data as Key, Value pair where Key is hostname of device and Values are its IP Addresses.

Now our data store is done, we can start with Juniper PYez ( to get the configs first.

We will be importing the Pyez modules, set the .yml input file location and run ‘for’ loop on our dictionary. We will store the backup config files as .txt file with hostnames as Title for easy accessibility. Don’t forget to import yaml module as we will be working on yaml file.

from jnpr.junos import Device
from jnpr.junos.exception import ConnectError
import yaml

input_file = '/home/sun/gitlab/device_list.yml'

for key, value in yaml.load(open(input_file)).items():

    dev_username = test
    dev_password = test
    dev = Device(host=value, user=dev_username, passwd=dev_password, port='830')

    except ConnectError as err:
        print ("Cannot connect to device: {0}".format(err))
    except Exception as err:
        print (err)

    config = str(dev.cli("show configuration | no-more", warning=False))

    #####Create/Write to Config to File

    file_name = key + '.txt'


That was pretty simple. Let me know if you have any issues. Now let’s work out how to push it to GIT.

We will be using the subprocess module to do this work for us where we will be running series of commands in serial to put the files across the gitlab. You are starting by going into particular directory which is your starting git project directory. You are looking at each branch within your git project using ‘git branch’ command and then checking out a particular branch on which you to work or store the data. In our case it’s Core_Network. Once you have moved to that, you can move into other specific folders and ‘mv’ your backup .txt files into this folder.

Once that is done, you will use git commands, like ‘git add –all’ to add all files as part of staging. ‘git commit –m “some description”’ to commit the files and then use ‘git push’ to push them to remote gitlab server.

Code will be:

from subprocess import PIPE
from subprocess import Popen
import sys
import os
import yaml
cmds =['cd /home/sun/gitlab/athena-test', 'git branch', 'ls -l', 'git checkout " Core_Network"', 'cd "Core Network"', 'cd "Device backups"', 'mv /home/sun/gitlab/*.txt /home/sun/gitlab/athena-test/"Core Network"/"Device backups"/', 'git add --all', 'git commit -m "Updated config files"', 'git push' ]
encoding = 'utf8'
p = Popen('/bin/sh', stdin=PIPE, stdout=PIPE, stderr=PIPE)
for cmd in cmds:
p.stdin.write(cmd + "\n")
print "Push to GitLab Completed"

One main thing you have to keep in mind is that you won’t be able to push the files until unless you have some remote servers configured under your server.

For example, mine is below where I have removed certain values and replaced them with xxx, yyy and ip address.. xxx is username, yyy is password and hostname  is gitlab server address.

sun@ $ git remote -v
origin https://xxx:yyy@<hostname>/athena-test.git (fetch)
origin https://xxx:yyy@<hostname>/athena-test.git (push)

Let’s see this in action by changing the config on one of the router.> edit
Entering configuration mode run show configuration system services ssh
root-login allow;
protocol-version v2;
max-sessions-per-connection 32;
connection-limit 20;
rate-limit 10;

[edit] set system services ssh connection-limit 10

[edit] show | compare
[edit system services ssh]
- connection-limit 20;
+ connection-limit 10;

[edit] commit
commit complete

Run the script now from CentOS Server

sun@ pwd


sun@ $ python

Successfully Collected Configuration from Device: Bristol_MX104

Successfully Collected Configuration from Device: Manchester_MX10003

Successfully Collected Configuration from Device: Glasgow_MX10003

Successfully Collected Configuration from Device: London_MX104

Successfully Collected Configuration from Device: Leeds_MX104

Push to GitLab Completed


You can see config was pushed and if we see the gitlab, it’s clearly showing the difference from the previous backup it had. Red one is one that is removed and Green one is what has been added.

So you can use this utility as version control of your configs and once you are happy with the configs you can push them to master for production use 🙂


GitLab side by side comparison


One last thing, if you have to run this as a cronjob on Centos, just edit the crontab file using ‘crontab –e’ and add the path to the script and at what particular time you want to run and that’s all.

I hope you liked this blog. Let me know if you have any queries.




Connecting OpendayLight to Juniper Routers via Netconf

Hi All

In this blog, we will look at configuring Juniper routers via Opendaylight which in turn uses netconf/restconf for making the connection.

Before we can start doing the configuration we need to create a Netconf connector between Opendaylight and Juniper routers. Also before that let’s first see what NETCONF is 🙂

Network Configuration Protocol (NETCONF) provides a mechanism to install, manipulate and delete the configuration of network devices. It uses an Extensible Markup Language (XML) based data encoding for the configuration data as well as the protocol messages. The NETCONF protocol operations are realized as remote procedure calls (RPCs).

OpenDaylight uses YANG modules to access the device via NETCONF and we can do config as well. In this post we will see how to configure ODL for NETCONF connections. This is tried method so please do this as listed and I have seen others methods may not work properly.

Below topology we will be using in this blog.

  • Juniper MXs are running on 18.2R1 and 17.4R1
  • OpendayLight Release is Oxygen 0.8.2


ODL-Netconf-Juniper1) In First instance, you need to enable netconf on Juniper

write@Manchester> show configuration system services netconf
ssh {
    connection-limit 10;
    rate-limit 5;


2) Download the 0.8.2 Oxygen Tar file from Opendaylight website and untar it.

Command “ tar –xvf karaf-0.8.2.tar.gz

This will create a directory called karaf-0.8.2 in same directory structure.

[root@Opendaylight-2 sun]# ls -l | grep karaf-0.8.2
drwxr-xr-x. 13 root root      4096 Jul 26 15:42 karaf-0.8.2
-rw-rw-r--.  1 sun  sun  358590049 Jul 24 13:46 karaf-0.8.2.tar.gz


3) Now create a file called, 99-netconf-connector.xml and paste the following contents in it

830 write write false true prefix:netty-event-executor global-event-executor prefix:binding-broker-osgi-registry binding-osgi-broker prefix:dom-broker-osgi-registry dom-broker prefix:netconf-client-dispatcher global-netconf-dispatcher prefix:threadpool global-netconf-processing-executor prefix:scheduled-threadpool global-netconf-ssh-scheduled-executor urn:opendaylight:params:xml:ns:yang:controller:md:sal:connector:netconf?module=odl-sal-netconf-connector-cfg&revision=2015-08-03

You have to change the details for the values mentioned in Red above according to first device you are trying to add. Don’t change anything else. However if your Junos version is other than 18.2 then you need to check the revision number of yang modules and put the correct date for field in Green above.

Once done, save the file.

4)  Now start the opendaylight using command:

[root@Opendaylight-2 sun]# ./karaf-0.8.2/bin/karaf
Apache Karaf starting up. Press Enter to open the shell now...
100% [========================================================================]
Karaf started in 18s. Bundle stats: 388 active, 389 total
    ________                       ________                .__  .__       .__     __
    \_____  \ ______   ____   ____ \______ \ _____  ___.__.|  | |__| ____ |  |___/  |_
     /   |   \\____ \_/ __ \ /    \ |    |  \\__  \ >  ___/|   |  \|    `   \/ __ \\___  ||  |_|  / /_/  >   Y  \  |
    \_______  /   __/ \___  >___|  /_______  (____  / ____||____/__\___  /|___|  /__|
            \/|__|        \/     \/        \/     \/\/            /_____/      \/

Hit '' for a list of available commands
and '[cmd] --help' for help on a specific command.
Hit '' or type 'system:shutdown' or 'logout' to shutdown OpenDaylight.


Install following packages, you don’t have to add any other at this moment of time:

feature:install odl-netconf-topology odl-restconf odl-netconf-connector-all

After installing, copy the file 99-netconf-connector.xml created above under directory karaf-0.8.2/etc/opendaylight/karaf/

cp 99-netconf-connector.xml karaf-0.8.2/etc/opendaylight/karaf/


5) After this, using POSTMAN or similar application, send a PUT request to following URL

PUT http://&lt;CONTROLLER-IP-ADDRESS:8181>/restconf/config/network-topology:network-topology/topology/topology-netconf/node/<node-name>

Same as before change the values in Red and Green accordingly for your case.




6) After this restart the opendaylight

Confirm: halt instance root (yes/no): yes

[root@Opendaylight-2 sun]# ./karaf-0.8.2/bin/karaf
Apache Karaf starting up. Press Enter to open the shell now...

At this point you should some messages like as mentioned in Karaf_Logs after adding the netconf-connector. Let it may take 10-20 minutes from here which is basically ODL is pulling all the Juniper Yang modules in its cache/schema folder.

Once that is done you should see the below message in karaf log which you can see using log:tail from opendaylight shell prompt.

| INFO  | sing-executor-22 | NetconfDevice   | 304 - org.opendaylight.netconf.sal-netconf-connector - 1.7.2 | RemoteDevice{Manchester}: Netconf connector initialized successfully

Once you get the message, your node has been mounted which you can check using GET request at following URL

GET http:// <CONTROLLER-IP-ADDRESS:8181/restconf/operational/network-topology:network-topology/topology/topology-netconf/node/<Node-name>/yang-ext:mount/


Now its ready to configure 🙂

Let’s configure a sample L3VPN using this

See the snapshot which is basically a PUT request with XML payload


Lets’s verify

write@Manchester> show configuration routing-instances odl-test
instance-type vrf;
interface xe-0/2/0.4000;
vrf-target target:2856:4000;
routing-options {
    protect core;
protocols {
    bgp {
        group ebgp {
            type external;
            peer-as 65101;
            neighbor {
                authentication-key "$9$CuyoAORhclMLNylJDkP3nylKvWx"; ## SECRET-DATA
                bfd-liveness-detection {
                    minimum-interval 100;
                    multiplier 3;


Here you go.. its working 🙂

That’s all for today.. I will do a separate blog for other service configurations via ODL. Let me know if you have any questions.




PCEP Initiated LSP using OpenDayLight and Juniper vMX

Hi All

In this post, we will look at Open day light controller working with Juniper vMXs and how we can use the controller to get the BGP, BGP-LS and PCEP working. Once everything is up and running we will use the Controller to initiate the PCEP initiated MPLS LSPs between 2 VMXs.

Sounds interesting? Let’s see how we can achieve this.

Before I go further, if you want to check anything on PCEP and some of its concept, I did a post on Juniper Northstar Controller some time ago which you can check.

Below is the topology we will be using where all Juniper VMXs are loaded in Virtual Control Plane mode and they have fxp0 interface in 192.168.71.x subnet. Open day light controller version is Nitrogen and we have booted it on CentOS 7.5 version.

There is Windows VM in same subnet also from where we will run the REST APIs calls to Open day light using POSTMAN App.

Topology Diagram
Topology Diagram


We will divide the post into 3 parts.

  • Configuring BGP/BGP-Link state between ODL and VMX-3.
  • Configuring PCEP session between all VMXs and ODL
  • Initiate MPLS LSP from ODL using PCEP

I am assuming that you already know how to start an ODL controller. However if you don’t know let me know and I can help you.

So lets start with 1) Configuring BGP/BGP-Link state between ODL and VMX-3.

If you already don’t know, Open day light versions in recent times doesn’t come auto-installed with all the features. You have to manually add them. You don’t need to download them individually. It’s just you need to activate them.

We will be configure the BGP and BGP-LS on VMX-3 first

Standard BGP config with IPv4 Unicast address family however for BGP-LS we have to enable a separate family traffic-engineering additionally.

root@VMX-3> show configuration protocols bgp
group opendaylight {
 type internal;
 description Controller;
 family inet {
 family traffic-engineering {
 peer-as 2856;

On ODL side, First install the BGP and restconf feature on karaf console using command

feature:install odl-restconf odl-bgpcep-bgp

Then using REST API we will enable the BGP Router-ID with Link State family


POST Request_BGP Router ID
POST Request_BGP Router ID

Then Configure the peer with specific BGP Parameters and families


POST Request_BGP Peer
POST Request_BGP Peer

We can check the status of BGP peering off course from VMX side but let’s see what comes up from ODL side


GET Request_BGP Peering
GET Request_BGP Peering

From VMX side:

root@VMX-3> show bgp neighbor
Peer: AS 2856 Local: AS 2856
 Description: Controller
 Group: opendaylight Routing-Instance: master
 Forwarding routing-instance: master
 Type: Internal State: Established Flags: <Sync>
 Last State: OpenConfirm Last Event: RecvKeepAlive
 Last Error: None
 Options: <Preference LocalAddress LogUpDown AddressFamily PeerAS Refresh>
 Options: <VpnApplyExport DropPathAttributes>
 Address families configured: inet-unicast te-unicast
 Path-attributes dropped: 128
 Local Address: Holdtime: 90 Preference: 170
 Number of flaps: 2
 Last flap event: RecvNotify
 Error: 'Cease' Sent: 0 Recv: 33
 Peer ID: Local ID: Active Holdtime: 90
 Keepalive Interval: 30 Group index: 0 Peer index: 0 SNMP index: 0
 I/O Session Thread: bgpio-0 State: Enabled
 BFD: disabled, down
 NLRI for restart configured on peer: inet-unicast te-unicast


BGP-LS configuration we did will be used to advertise the Traffic Engineering database to Controller. You can see the routes advertised using lsdist.0 table in juniper.

Snippet below:

root@VMX-3> show route table lsdist.0
lsdist.0: 11 destinations, 11 routes (11 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both
NODE { AS:2856 Area: IPv4: OSPF:0 }/1152
 *[OSPF/10] 02:02:38
NODE { AS:2856 Area: IPv4: OSPF:0 }/1152
 *[OSPF/10] 02:02:43
NODE { AS:2856 Area: IPv4: OSPF:0 }/1152
 *[OSPF/10] 02:02:38
NODE { AS:2856 Area: IPv4: OSPF:0 }/1152
 *[OSPF/10] 02:02:31
LINK { Local { AS:2856 Area: IPv4: }.{ IPv4: } Remote { AS:2856 Area: IPv4: }.{ } OSPF:0 }/1152
 *[OSPF/10] 02:02:31


2) Now let’s configure the PCEP

On VMX (This will be repeated on all with change in local address)

root@VMX-3> show configuration protocols pcep
pce odl {
 destination-port 4189;
 pce-type active stateful;

If you have any firewall, make sure to allow port 4189 between Controller and VMXs.

On ODL, we need to install odl-bgpcep-pcep feature

There is no other config to do. As soon as you install this feature, you should see PCEP status up.

Let’s see it from VMX-4


root@VMX-4> show path-computation-client status
Session Type            Provisioning Status
odl     Stateful Active On           Up

LSP Summary
 Total number of LSPs : 0
 Static LSPs : 0
 Externally controlled LSPs : 0
 Externally provisioned LSPs : 0/16000 (current/limit)
 Orphaned LSPs : 0

odl (main)
 Delegated : 0
 Externally provisioned : 0

From ODL side:

GET Request_PCEP Status
GET Request_PCEP Status

3)      PCEP Initiated LSP

Now, we will configure the LSP from VMX-3 to VMX-4 between their Loopback IPs.


You can see we haven’t given any ERO while provisioning the LSP. ODL has auto calculated the path and you can verify in VMX-3

PCEP LSP ADD with No Ero
PCEP LSP ADD with No Ero
root@VMX-3> show mpls lsp name test-pcep-2 extensive
Ingress LSP: 1 sessions
 From:, State: Up, ActiveRoute: 0, LSPname: test-pcep-2
 ActivePath: (primary)
 LSPtype: Externally provisioned, Penultimate hop popping
 LSP Control Status: Externally controlled
 LoadBalance: Random
 Encoding type: Packet, Switching type: Packet, GPID: IPv4
 LSP Self-ping Status : Enabled
 *Primary State: Up, Preference: 200
 Priorities: 0 0
 External Path CSPF Status: external
 SmartOptimizeTimer: 180
 Flap Count: 0
 MBB Count: 0
 Received RRO (ProtectionFlag 1=Available 2=InUse 4=B/W 8=Node 10=SoftPreempt 20=Node-ID):
 12 May 24 12:10:08.334 Self-ping ended successfully
 11 May 24 12:10:07.830 EXTCTRL LSP: Sent Path computation request and LSP status
 10 May 24 12:10:07.830 EXTCTRL_LSP: Computation request/lsp status contains: signalled bw 0 req BW 0 admin group(exclude 0 include any 0 include all 0) priority setup 0 hold 0
 9 May 24 12:10:07.829 Selected as active path
 8 May 24 12:10:07.828 EXTCTRL LSP: Sent Path computation request and LSP status
 7 May 24 12:10:07.828 EXTCTRL_LSP: Computation request/lsp status contains: signalled bw 0 req BW 0 admin group(exclude 0 include any 0 include all 0) priority setup 0 hold 0
 6 May 24 12:10:07.828 Up
 5 May 24 12:10:07.828 Self-ping started
 4 May 24 12:10:07.828 Self-ping enqueued
 3 May 24 12:10:07.828 Record Route:
 2 May 24 12:10:07.824 Originate Call
 1 May 24 12:10:07.824 EXTCTRL_LSP: Received setup parameters ::
 Created: Thu May 24 12:10:07 2018
Total 1 displayed, Up 1, Down 0


You can do various operations like Deleting LSP, Modifying LSP etc from REST API.

One thing which we can’t do at the moment using PCEP is configuring Point to Multipoint LSP as standard is still being drafted for this but I hope it will come out soon.

So that’s all for now, I hope you enjoyed it and let me know your feedback.






Hi All

This time we will be looking at EVPN, its configuration on JunOS and how it is different from VPLS.

Currently if service provider has to join customer’s multiple sites via Layer 2, only option is VPLS. VPLS can be LDP based or BGP based.

BGP based VPLS has advantages that you can use RRs to scale however VPLS as a whole has a disadvantages that:

  • We can’t do active-active multihoming with both links from CE to PE.
  • Control plane MAC-Learning is not possible.
  • L2 Loop detection is not possible.
  • VPLS consumes less in control plane however more MPLS labels (because MAC learning relies on a different label for each remote site) than EVPN.

EVPN is immune to all the above problems and it’s only based upon BGP so we don’t have to fight between LDP vs BGP advantages.

Underlying EVPN can be used with VXLAN or MPLS however solution which I am going to discuss is based upon MPLS.

Look at the diagram below. We have 3 sites basically 3 VMs all part of same IP Network and they are connected to same EVPN instances on 3 different Juniper routers via switch in their path.

EVPN Topology

Let’s see config on Manchester Juniper PE router.

You can see its fairly straightforward config with same parameters as L3VPNs except instance-type is evpn and we need to use protocols evpn to define parameters to limit the mac and ip if we want.

write@re1.Manchester > show configuration routing-instances evpn-1
instance-type evpn;
vlan-id 1200;
interface xe-1/0/0:0.1200;
vrf-target target:2856:1200;
protocols {
 evpn {
 interface-mac-limit {
 packet-action drop;
 interface-mac-ip-limit {
 interface xe-1/0/0:0.1200;
 label-allocation per-instance;

From RR point of view, we need to add family evpn under BGP on all PEs and RR.

write@re1.Manchester > show configuration protocols bgp
path-selection external-router-id;
drop-path-attributes 128;
authentication-algorithm md5;
tcp-mss 4096;
group LAB-RR {
 type internal;
 family inet-vpn {
 family l2vpn {
 family evpn {

We will be doing the same configs on rest 2 PEs.

write@re1.Manchester > show evpn instance evpn-1 extensive
Instance: evpn-1
 Route Distinguisher:
 VLAN ID: 1200
 Per-instance MAC route label: 119
 Per-instance multicast route label: 120
 Duplicate MAC detection threshold: 5
 Duplicate MAC detection window: 180
 MAC database status Local Remote
 MAC advertisements: 1 2
 MAC+IP advertisements: 1 2
 Default gateway MAC advertisements: 0 0
 Number of local interfaces: 3 (3 up)
 Interface name ESI Mode Status AC-Role
 et-1/1/0.1200 00:00:00:00:00:00:00:00:00:00 single-homed Up Root
 xe-1/0/0:0.1200 00:00:00:00:00:00:00:00:00:00 single-homed Up Root
 xe-1/0/0:0.1210 00:00:00:00:00:00:00:00:00:00 single-homed Up Root
 Number of IRB interfaces: 0 (0 up)
 Number of protect interfaces: 0
 Number of bridge domains: 1
 VLAN Domain ID Intfs / up IRB intf Mode MAC sync IM route label SG sync IM core nexthop
 1200 3 3 Extended Enabled 120 Enabled
 Number of neighbors: 4
 Address MAC MAC+IP AD IM ES Leaf-label 0 0 0 1 0 1 1 0 1 0 0 0 0 1 0 1 1 0 1 0
 Number of ethernet segments: 0

Some key take away from above is that due to config “label-allocation per-instance” we are seeing one MPLS Label for the whole EVPN routing instance.

write@re1.Manchester > show route table mpls.0 label 119
mpls.0: 45 destinations, 45 routes (45 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

119 *[EVPN/7] 3d 20:05:21, routing-instance evpn-1, route-type Ingress-MAC, vlan-id 1200
 to table evpn-1.evpn-mac.0

ESI (Ethernet Segment Identifier) is all zeros for PE which is single homed to CE. In active-active multihoming, an Ethernet segment appears as a LAG to the CE device.

Let’s check the mac-table on PE. So you can see   00:0c:29:34:04:26 is learned dynamically by Manc PE over xe-1/0/0:0/1200 interface. This is still Data Plane learning and with EVPN there is no difference. However look at MAC Flags for other 2 MAC addresses. DC corresponds to Dynamic Control MAC means they are learned via Control Plane (using BGP)

write@re1.Manchester > show evpn mac-table instance evpn-1
MAC flags       (S -static MAC, D -dynamic MAC, L -locally learned, C -Control MAC
O -OVSDB MAC, SE -Statistics enabled, NM -Non configured MAC, R -Remote PE MAC, P -Pinned MAC)
Routing instance : evpn-1
Bridging domain : __evpn-1__, VLAN : 1200
MAC                         MAC      Logical          NH     MAC         active
address                    flags    interface        Index  property    source
00:0c:29:34:04:26   D        xe-1/0/0:0.1200
00:0c:29:37:55:3d   DC                        1048585  
00:0c:29:55:5a:45   DC                        1048584  

Evpn has also learned the IP Address and added in arp-table so you can see MAC/IP Association.

write@re1.Manchester > show evpn arp-table instance evpn-1
INET MAC Logical Routing Bridging
address address interface instance domain 00:0c:29:34:04:26 xe-1/0/0:0.1200 evpn-1 __evpn-1__ 00:0c:29:37:55:3d evpn-1 __evpn-1__ 00:0c:29:55:5a:45 evpn-1 __evpn-1__

Same thing you can see in routing table as well.

There are several types of routes in EVPN, Type 1, 2, 3, 5, 6 etc.. Type 2 is MAC and IP Route which shows relationship between them however Junos shows that also in 2 ways. Type 2 route as pure MAC and type 2 route as MAC/IP.

Type 3 routes are required for Broadcast, Unknown Unicast and Multicast (BUM) traffic delivery across EVPN networks. Type 3 advertisements provide information about P-tunnels that should be used to send BUM traffic. Without Type 3 advertisements, ingress router would not know how to deliver BUM traffic to other PE devices that comprise given EVPN instance.

write@re1.Manchester > show route table evpn-1
evpn-1.evpn.0: 11 destinations, 11 routes (11 active, 0 holddown, 0 hidden)
+ = Active Route, - = Last Active, * = Both

 *[EVPN/170] 3d 19:18:39
 *[BGP/170] 1d 02:03:17, localpref 100, from
 AS path: I, validation-state: unverified
 > to via xe-0/0/0:1.0
 *[BGP/170] 03:13:24, localpref 100, from
 AS path: I, validation-state: unverified
 > to via et-0/1/0.0, Push 945
 *[EVPN/170] 3d 19:18:34
 *[BGP/170] 01:53:03, localpref 100, from
 AS path: I, validation-state: unverified
 > to via xe-0/0/0:1.0
 *[BGP/170] 03:13:24, localpref 100, from
 AS path: I, validation-state: unverified
 > to via et-0/1/0.0, Push 945
3: IM
 *[EVPN/170] 6d 22:17:38
3: IM
 *[BGP/170] 03:13:24, localpref 100, from
 AS path: I, validation-state: unverified
 > to via et-0/1/0.0
3: IM
 *[BGP/170] 1d 02:03:17, localpref 100, from
 AS path: I, validation-state: unverified
 > to via xe-0/0/0:1.0
3: IM
 *[BGP/170] 1d 02:03:17, localpref 100, from
 AS path: I, validation-state: unverified
 > to via xe-0/0/0:2.0
3: IM
 *[BGP/170] 03:13:24, localpref 100, from
 AS path: I, validation-state: unverified
 > to via et-0/1/0.0, Push 945


Let’s do a ping test from VM ( connected to London to VM ( connected to Manchester PE via EVPN Network.

For completeness, I have shown the arp-table for London EVPN-1.

write@re0.London > show evpn arp-table instance evpn-1
INET MAC Logical Routing Bridging
address address interface instance domain 00:0c:29:34:04:26 evpn-1 __evpn-1__ 00:0c:29:37:55:3d xe-0/2/0.1200 evpn-1 __evpn-1__ 00:0c:29:55:5a:45 evpn-1 __evpn-1__

You can see Ping works without any loss.


So that’s all for EVPN. Let me know if you have any queries and I hope to show you more in next blogs about EVPN.

BBye 🙂


Segment Routing v/s RSVP-TE?

SR (Segment Routing) is new and trending topic these days in Telecom Networks. It’s promising and some vendors are pushing for it because of the way we can leverage SDN Controller to steer the traffic through the Network plus how it will remove need of LDP/RSVPE-TE from core however i think there are still some of the use cases where it lacks some capabilities currently. I hope in future all these areas will be fixed and SR becomes THE Option of choice for all Service Providers. These are all my opinions and it would be good to know your views on it.

1)      Bandwidth Reservation issue –> Using SR we can’t reserve the bandwidth in our Network for each LSP as we can do with RSVP-TE. Bandwidth reservation can be critical in some Service provider/Broadcast networks to provide the customer with dedicated bandwidth. We can argue that Controller at the Top can look at the whole Network and would be able to easily manage the reservations however Controller is a single point of failure and I don’t think we can depend upon Controller for this crucial behaviour.?

2)      Lack of Multicast P2MP Support –> Multicast proposes more challenge for the segment routing. SR can only replace Point to point LDP/RSVP-TE however some of the Telecom Networks uses P2MP Multicast services as part of NG-MVPN and for those we still need to depend on RSVP-TE . Moreover MPLS-based multicast solutions have matured now after many years’ of development. I think keeping 2 Technologies i.e one for P2P L2/L3VPN and other for P2MP MVPN will add complexity only to network.

3)      Depth of MPLS Label Stack –> We know that forwarding packets need to push a SR header with a list of segments(labels). Now there are 2 main types of SR Labels. One is Node and other is Adjacency (link). To provide granularity to route the traffic via 15-20 hops we need to push more Adjacency labels at Ingress PE accordingly. This depth of label stack may be a challenge for some type of devices.

Plz see some of the labels stack present in hardware:  (Courtesy:

Linux (kernel 4.10): 2-3 SID’s

Low end off the shelf (merchant) silicon, e.g. BCM Trident2: 3-5 SID’s

High end off the shelf (merchant) silicon, e.g BCM Jericho1 : 4-7 SID’s

Vendor’ silicon, e.g. Juniper’ Trio: 4-10+ SID’s

Even though Vendor may be able to support 15-20 Label stack, we can end up in payload efficiency and MTU issues i.e. because of big size of the header will reduce the efficiency of payload.

4)      State Issues –> One major advantage for segment routing proposed was that the State is only maintained at the head-end. No state is maintained at mid-points and tail-ends. This is good in case if we have Node and Adjacency/Link labels only however there are proposals for Prefix segment Labels also which will increase the state on all the points in network and I don’t think behaviour will be different from LDP/RSVP-TE then.

In case of centrally controlled environment where Controller will take care of everything it will be difficult for Operations Teams to troubleshoot in case anything goes wrong in Network as they need to know the architecture of each device whether it is capable of getting around the Label stack issue via that device. We may be thinking of putting low end devices near to Customer edge as PEs and high end in middle of core, however due to label stack issue we may need to put high end routers only everywhere.

I am not against SR however i would be really pleased if these issues can be taken care or already available (i may well be living in old times) however from my perspective, there is scalability issue which limits application scenarios for segment routing. It may be better for cases where service provider is mostly providing  unicast L2/L3VPN services.

Let me know your views on this and how you are using SR in your environment 🙂