Tag Archives: Junos

Juniper Northstar SDN Controller – Part 2

6 Oct 2017Automation, Juniper, Junos, Monitoring, MPLS, Networking, NFV, RSVP, SDNController, Juniper, Junos, LSP, MPLS, Networking, Northstar, P2MP, RSVP, SDNMohit

Following on my earlier blog on Northstar here: https://networkzblogger.com/2017/03/17/juniper-northstar-wan-sdn-controller, recently I got chance to work on next release of it which has among other things is ability to initiate P2MP (Point to Multipoint) LSPs. P2MPs are big use case in Media and Broadcast network and ability to create them via controller would be too helpful. However there is a catch. As discussed in my earlier blog, the NorthStar (NS) Controller relies on PCEP (Path Computation Element Protocol) to deploy a path between the PCC router and PCE (Controller). Currently P2MPs are not initiated by PCEP or its standard is not ratified. So Juniper have come up with another way of configuring it and that’s via Netconf. NETCONF provides mechanisms to install, manipulate, and delete the configuration of network devices. Its operations are realized on top of a simple Remote Procedure Call (RPC) layer. The protocol messages are exchanged on top of a secure transport protocol like SSH etc.

In this blog, instead of looking at PCEP based LSPs from Northstar we will explore netconf functionality and what other features have been introduced in new ns version.

Below is our current model which is built using TED (Traffic Engineering Database) by Northstar and if you look closely there are 2 devices which have PCEP session up because they have correct Junos code on it (15.1F6 and later) however all others are having netconf session Up even if they are on Junos 10, 12, 14 etc. which is cool thing. So as long as you have netconf stanza added in Junos config and have ssh connectivity that is all Northstar need to connect to devices.

Lets start by configuring a P2MP LSP via Northstar

You can see 2 options here for provisioning method. One is PCEP and other is Netconf.

We will choose Netconf and fill other bits.

We have kept Path as dynamic however we can choose required path to TE it more. Under Advanced Tab, you will see P2MP Name field, in which we have added the P2MP name.

All others field you can pretty much keep default.

Once you submit it, Northstar will open a netconf session on port 830 towards headend router which is M320 in our case and push and commit the config to it.

You can see above LSP has become Active and its showing the path as well which this LSP is taking. Now one of the biggest difference between PCEP created LSP and one created from Netconf is that Netconf LSPs will be part of startup-config in Junos as the configs are committing to it so it can be slow process getting your LSP up based upon commit time. Also all Netconf created LSPs are basically shown as PCC Controlled. However PCEP just sent LSP state to network to build E2E path rather than config. PCEP LSP config still resides in NS database and LSPs are created within seconds and are PCE Initiated.

M320> show configuration protocols mpls label-switched-path demo-0610
from 10.198.123.203;
to 10.198.123.103;
p2mp demo-0610-p2p;
primary demo-0610.p0 {
 apply-groups demo-0610-p2p;
}

M320> show configuration groups demo-0610-p2p
protocols {
 mpls {
 label-switched-path <*> {
 primary <*> {
 bandwidth 10m;
 priority 7 7;
 }
 }
 }
}

Ok so that’s for P2MP LSPs which is clean. In 3.1.0 one of the issue we found was related to commit process. Suppose you have 10 LSPs to be created from one source to destination. With Netconf, NS will commit 10 times individually for those LSPs which can be time consuming on some of the MX104s, MX80s with less CPU power. Juniper is looking to change this and putting the commit in batches to decrease the overall time and commit process which would be excellent J

So we have seen now how P2MP LSPs are created via Netconf however we haven’t seen how Netconf parameters are configured on NS as with netconf you can see the analytics data as well which is populated by Telemetry. We will see Telemetry in some other blog.

Under Administration -> Device Profiles we have to set the parameters for individual device.

We enable Netconf and add login details and password. You can test the connectivity as well from NS before actually trying to provision the network.

Apart from P2MP, another thing which has been introduced is while provisioning the LSP you can select which routing method you need to choose. There are many methods starting from default to routebyPCC, etc. default means that NS will calculate the path and routebyPCC means routers will calculate the path and NS won’t be having any say in it.

Another new feature which has been introduced in release 3.1.0 is setting the current path as explicit.

So above P2MP LSP I created was just dynamic however if we want to explicitly make this path as Strict so that LSP doesn’t change path based upon the network conditions we can configure it as below.

If we see the CLI now, NS has filled strict path in it.

M320> show configuration protocols mpls path demo-0610.p0
10.177.177.5 strict;
10.0.0.245 strict;

Ok that’s all for this blog. I hope you like it and let me know your views if you are looking at using NS for your network and if you are already, what are your use cases J

Mohit Mittal

Ansible on JunOS

5 Sep 2017Automation, Cisco, Juniper, Junos, NetworkingAnsible, Cisco, Juniper, Junos, Networking, puppetMohit

Hi All, first of all sorry for coming out late with next blog. Was busy in some personal and official stuff.

Also during past few days, I have been exploring having Ansible set up in our network for ease of configuring and having a centralised place to do some configuration on single or all boxes at once.

Ansible if you don’t know is Configuration Management, software provisioning tool. Ansible is in same league as Puppet, Chef, Salt provisioning tool but its different from them in some sense like Pull vs Push, Stateless vs Stateful etc. We will discuss these difference below but Ansible on top provides configuration/provisioning support for Network engineers in a sense that it has modules from different vendors like Cisco, Huawei, Arista, Nokia and Juniper. We will specifically discuss about Junos here.

Juniper provides support for using Ansible to deploy devices running the Junos operating system (Junos OS). The Juniper Networks Ansible library, which is hosted on the Ansible Galaxy website under the role junos, enables you to use Ansible to perform specific operational and configuration tasks on devices running Junos OS, including installing and upgrading, deploying specific devices in the network, loading configuration changes, retrieving information, and resetting, rebooting, or shutting down managed devices.

I have just started to explore Ansible so I am really Amateur in this area however may be after some months of work I will be in position to provide more details on this 🙂 . Before we dive into some examples let’s review what I said before regarding differences.

Push vs Pull –> Puppet basically works on Pull mechanism where its hosts periodically pulls the configurations from server which is good for some things but not if you want change to deployed asap. On the other hand Ansible works in Push model where config is applied instantly to nodes/hosts.

Stateless vs Stateful –> Ansible works in stateless mode where to use Ansible, nothing needs to be installed on Hosts i.e. switches/routers. Ansible and other libraries are installed on Server which is controller and it connects to nodes/hosts via SSH/Netconf.

For Ansible to work with Junos, 3 requirements needs to be fulfilled first on server.

1) pip install ncclient (this is python lib for netconf)

2) pip install junos-eznc (this is python lib for Junos)

3) Install Juniper.junos Galaxy role using command:

ansible-galaxy install Juniper.junos

Once this is done, we can run raw modules from Ansible server as Ad-hoc commands which basically uses SSH instead of netconf.

I am running ansible on CentOS 6.9

mmittal@ANS01$ cat /etc/redhat-release
CentOS release 6.9 (Final)

So basically here we will be using raw module to check the version on host and we will provide the username with it and –k option will invoke us to put password.

ansible -v 10.198.123.103 -m raw -a "show version" -u mmittal –k
SSH password:
10.198.123.103 | SUCCESS | rc=0 >>
Hostname: MX-104-PE-Volvo
Model: mx104
Junos: 15.1F6.9
JUNOS Base OS boot [15.1F6.9]
JUNOS Base OS Software Suite [15.1F6.9]
JUNOS Crypto Software Suite [15.1F6.9]
JUNOS Packet Forwarding Engine Support (MX104) [15.1F6.9]
JUNOS Web Management [15.1F6.9]
JUNOS Online Documentation [15.1F6.9]
JUNOS Services Application Level Gateways [15.1F6.9]
JUNOS Services Jflow Container package [15.1F6.9]
JUNOS Services Stateful Firewall [15.1F6.9]
JUNOS Services NAT [15.1F6.9]
JUNOS Services RPM [15.1F6.9]
JUNOS Services Captive Portal and Content Delivery Container package [15.1F6.9]
JUNOS Macsec Software Suite [15.1F6.9]
JUNOS Services Crypto [15.1F6.9]
JUNOS Services IPSec [15.1F6.9]
JUNOS Kernel Software Suite [15.1F6.9]
JUNOS Routing Software Suite [15.1F6.9]
Shared connection to 10.198.123.103 closed.

This adhoc commands lets you check things without having to do any real programming however real use of Ansible comes via way of playbooks which are basically scripts in layman term. Under playbook we will mention the module which want to run and tasks to be performed. Before running Ansible playbook it is better to talk about one important file name called ansible.cfg which basically resides in etc/ansible/ansible.cfg

However ansible.cfg is picked up in following order and it is recommended to have our own ansible.cfg in current/home directory so that we can control the parameters we want to have.

* ANSIBLE_CONFIG (an environment variable)
* ansible.cfg (in the current directory)
* .ansible.cfg (in the home directory)
* .ansible.cdg (in /etc/ansible/ansible.cfg)

Example from my ansible.cfg which apart from standard defaults is also pointing to hostfile where all IP Addresses of routers/switches will reside.

mmittal@ANS01$ cat ansible.cfg
[defaults]
hostfile = ./ansible_hosts
host_key_checking = false
timeout = 5
log_path=./ansible.log

Lets see one example of playbook.

So in this playbook we are adding a task of running multiple commands on 2 hosts and module we have used in junos_command and we are printing the output on session.

mmittal@ANS01$ cat ansible_multiplecommands.yml
---
- name: show version and other user level commands
 hosts: 10.198.123.100, 10.198.123.103
 roles:
 - Juniper.junos
 gather_facts: no
 connection: local
tasks:
 - name: run multiple commands on remote nodes
 junos_command:
 commands:
 - show version
 - show interfaces

register: print_output

- debug: var=print_output.stdout_lines

To run this playbook we have to use the following command:

mmittal@ANS01$ ansible-playbook ansible_multiplecommands.yml -u mmittal -k
SSH password:

PLAY [show version and other user level commands] *************************************************************************************************************************************************************

TASK [run multiple commands on remote nodes] ******************************************************************************************************************************************************************
ok: [10.198.123.103]
ok: [10.198.123.100]

TASK [debug] **************************************************************************************************************************************************************************************************
ok: [10.198.123.100] => {
 "print_output.stdout_lines": [
 [
 "Hostname: re1.MX104_PE_Pagani",
 "Model: mx104",
 "Junos: 15.1F6.9",
 "JUNOS Base OS boot [15.1F6.9]",
 "JUNOS Base OS Software Suite [15.1F6.9]",
 "JUNOS Crypto Software Suite [15.1F6.9]",
 "JUNOS Packet Forwarding Engine Support (MX104) [15.1F6.9]",
 "JUNOS Web Management [15.1F6.9]",
 "JUNOS Online Documentation [15.1F6.9]",
 "JUNOS Services Application Level Gateways [15.1F6.9]",
 "JUNOS Services Jflow Container package [15.1F6.9]",
 "JUNOS Services Stateful Firewall [15.1F6.9]",
 "JUNOS Services NAT [15.1F6.9]",
 "JUNOS Services RPM [15.1F6.9]",
 "JUNOS Services Captive Portal and Content Delivery Container package [15.1F6.9]",
 "JUNOS Macsec Software Suite [15.1F6.9]",
 "JUNOS Services Crypto [15.1F6.9]",
 "JUNOS Services IPSec [15.1F6.9]",
 "JUNOS Kernel Software Suite [15.1F6.9]",
 "JUNOS Routing Software Suite [15.1F6.9]"
 ],
 [
 "Physical interface: ge-0/0/0, Enabled, Physical link is Up",
 " Interface index: 154, SNMP ifIndex: 512",
 " Description: Connected to MX104 RR-3_ge-0/1/0",
 " Link-level type: Ethernet, MTU: 1600, MRU: 1608, LAN-PHY mode,",
 " Speed: 1000mbps, BPDU Error: None, MAC-REWRITE Error: None,",
 " Loopback: Disabled, Source filtering: Disabled, Flow control: Enabled,",
 " Auto-negotiation: Enabled, Remote fault: Online",
 " Pad to minimum frame size: Disabled",
 " Device flags : Present Running",
 " Interface flags: SNMP-Traps Internal: 0x0",
 " CoS queues : 8 supported, 8 maximum usable queues",
 " Current address: 54:1e:56:f7:78:00, Hardware address: 54:1e:56:f7:78:00",
 " Last flapped : 2017-08-18 13:32:41 GMT (2w3d 21:51 ago)",
 .
.
(o/p trunacated)
.
.
.
.
 ]
 ]
}
ok: [10.198.123.103] => {
 "print_output.stdout_lines": [
 [
 "Hostname: MX-104-PE-Volvo",
 "Model: mx104",
 "Junos: 15.1F6.9",
 "JUNOS Base OS boot [15.1F6.9]",
 "JUNOS Base OS Software Suite [15.1F6.9]",
 "JUNOS Crypto Software Suite [15.1F6.9]",
 "JUNOS Packet Forwarding Engine Support (MX104) [15.1F6.9]",
 "JUNOS Web Management [15.1F6.9]",
 "JUNOS Online Documentation [15.1F6.9]",
 "JUNOS Services Application Level Gateways [15.1F6.9]",
 "JUNOS Services Jflow Container package [15.1F6.9]",
 "JUNOS Services Stateful Firewall [15.1F6.9]",
 "JUNOS Services NAT [15.1F6.9]",
 "JUNOS Services RPM [15.1F6.9]",
 "JUNOS Services Captive Portal and Content Delivery Container package [15.1F6.9]",
 "JUNOS Macsec Software Suite [15.1F6.9]",
 "JUNOS Services Crypto [15.1F6.9]",
 "JUNOS Services IPSec [15.1F6.9]",
 "JUNOS Kernel Software Suite [15.1F6.9]",
 "JUNOS Routing Software Suite [15.1F6.9]"
 ],
 [
 "Physical interface: lc-0/0/0, Enabled, Physical link is Up",
 " Interface index: 142, SNMP ifIndex: 506",
 " Speed: 800mbps",
 " Device flags : Present Running",
 " Link flags : None",
 " Last flapped : Never",
 " Input packets : 0",
 " Output packets: 0",
 "",
 " Logical interface lc-0/0/0.32769 (Index 329) (SNMP ifIndex 507)",
 " Flags: Encapsulation: ENET2",
 " Bandwidth: 0",
 " Input packets : 0",
 " Output packets: 0",
 " Protocol vpls, MTU: Unlimited",
 " Flags: Is-Primary",
 "",
(o/p trunacated)
.
.
.
 ]
 ]
}

PLAY RECAP ****************************************************************************************************************************************************************************************************
10.198.123.100 : ok=2 changed=0 unreachable=0 failed=0
10.198.123.103 : ok=2 changed=0 unreachable=0 failed=0

So that’s all for today.. Its very basic intro to Ansible on Junos however I hope you get an idea and will try to use it in your network 🙂

Regards

Mohit

JUNIPER JUNOS COMMAND SERIES – 3

31 Jul 2017Juniper, Junos, NetworkingJuniper, Junos, Junos cheat sheet, Junos_commands, NetworkingMohit

Hi All, lets continue our useful Junos command series by looking at 2 more interesting commands. One is another flexibility which Juniper provides and 2^nd is to see the command structure in way which can be directly pasted on CLI.

So this is our example policy config from MX104:

MX104-PE> show configuration policy-options policy-statement test
term 1 {
 from community test;
 then accept;
}
term 2 {
 from neighbor 1.1.1.1;
 then accept;
}
term 3 {
 then reject;

Now lets suppose you need to add one term (term 4) between before term 3 so that it doesn’t get reject by last reject term. Lets puts a term 4 and see what’s the result.

[edit policy-options policy-statement test]
MX104-PE# set term 4 from family inet

[edit policy-options policy-statement test]
MX104-PE# set term 4 then accept

[edit policy-options policy-statement test]
MX104-PE# show
term 1 {
 from community test;
 then accept;
}
term 2 {
 from neighbor 1.1.1.1;
 then accept;
}
term 3 {
 then reject;
}
term 4 {
 from family inet;
 then accept;
}

Now if you see above Junos has added the term 4 at the end which won’t be useful to us if we commit now as term 3 is reject and term 4 won’t be validated at all because of reject term 3 above it. So to get away with this problem Junos provides us one command “insert” which will insert the term 4 before term 3. Let’s see it in action.

[edit policy-options policy-statement test]
MX104-PE# insert term 4 before term 3

[edit policy-options policy-statement test]
MX104-PE# show
term 1 {
 from community test;
 then accept;
}
term 2 {
 from neighbor 1.1.1.1;
 then accept;
}
term 4 {
 from family inet;
 then accept;
}
term 3 {
 then reject;
}

Now lets check the another command which is very easy hack

Sometimes you need the configuration from Juniper in set form so that you can paste it directly on the other or same box after some modifications.

This is our example configuration:

show configuration interfaces ge-0/1/8
vlan-tagging;
mtu 1522;
encapsulation vlan-ccc;
unit 601 {
 encapsulation vlan-ccc;
 vlan-id 601;
 family ccc;
}

Now to get the set form of this configuration, Junos gives us this command:

show configuration interfaces ge-0/1/8 | display set
set interfaces ge-0/1/8 vlan-tagging
set interfaces ge-0/1/8 mtu 1522
set interfaces ge-0/1/8 encapsulation vlan-ccc
set interfaces ge-0/1/8 unit 601 encapsulation vlan-ccc
set interfaces ge-0/1/8 unit 601 vlan-id 601
set interfaces ge-0/1/8 unit 601 family ccc

This is exact same config but in separate form and can be easily copy pasted from top edit mode on other device.

In next blogs we will see more commands to copy paste the config without set form.

So that’s all, I hope you liked this article as well and will make use of these commands in your day to day operational work or troubleshooting.

Regards

Mohit Mittal

RSVP Messages in Juniper JunOS

6 Jul 2017Juniper, Junos, MPLS, Networking, RSVPCCC, Juniper, Junos, LSP, MPLS, Networking, RSVP, TCP/IPMohit

RSVP (Resource Reservation Protocol) is a transport layer protocol designed to reserve resources across a network for an integrated services Internet. RSVP is not a routing protocol and was designed to interoperate with current and future routing protocols.

RSVP by itself is rarely deployed in telecom networks today but the traffic engineering extension of RSVP, or RSVP-TE, is becoming more widely accepted nowadays in many QoS-oriented networks

In this blog we will see the RSVP messages which flows while setting up the E2E LSP between 2 PEs.

Following model will be used to understand the behaviour.

LSP we will configure is TEST-MX960-MX104 between MX960 (Hostname : Bentley) and MX104 (Hostname Pagani) via M320 and M120.

Let’s configure the LSP as below from MX960 to MX104 (loopback IP: 10.198.123.100) with strict path through M320 and M120.

re1.bentley> show configuration protocols mpls label-switched-path TEST-MX960-MX104
to 10.198.123.100;
bandwidth 100m;
optimize-timer 900;
preference 200;
priority 5 0;
primary Bentley-Pagani;

re1.bentley> show configuration protocols mpls path Bentley-Pagani
10.0.0.93 strict;
10.0.0.41 strict;
10.0.0.170 strict;

Before we see the RSVP session details, lets see the message interactions happening at each device from Ingress to Egress. We enabled the RSVP traceoptions in order to capture the packets.

As soon as LSP is configured, RSVP new session is built with tunnel ID (44394 in our case) which is unique for this LSP and will be present in all messages.

Jun 25 18:32:31.822264 RSVP new Session 10.198.123.100(port/tunnel ID 44394 Ext-ID 10.198.123.205) Proto 0, session ID 51419

Jun 25 18:32:31.822301 RSVP new path state, session 10.198.123.100(port/tunnel ID 44394 Ext-ID 10.198.123.205) Proto 0

Path Messages:

Path message will be sent by Ingress PE MX960 towards MX104 hop by hop using the strict path we configured or will be based on IGP path in case no path has been defined.

MX960 will send the RSVP Send path message which will be received by Transit routers which in turn will send their own Path messages.

On MX960:

Jun 25 18:32:31.824365 RSVP send Path 10.198.123.205->10.198.123.100 Len=272 ge-1/1/7.0 flags=0x1 ttl=255
Jun 25 18:32:31.824385 Integty Len 36 flag 0x0 key 0x00005e00000a seq 0xbf015059de530a00 digest 0x75c574bd 0x3c7e8ecb 0x435976f8 0x408b3263
Jun 25 18:32:31.824399 MessageID Len 12 Msg_ID: 878279 Epoch: 2641670 (Ack Desired)
Jun 25 18:32:31.824415 Session7 Len 16 10.198.123.100(port/tunnel ID 44394 Ext-ID 10.198.123.205) Proto 0
Jun 25 18:32:31.824431 Hop Len 12 10.0.0.94/0x80000009
Jun 25 18:32:31.824443 Time Len 8 30000 ms
Jun 25 18:32:31.824464 SrcRoute Len 28 10.0.0.93 S 10.0.0.41 S 10.0.0.170 S
Jun 25 18:32:31.824477 LabelRequest Len 8 EtherType 0x800
Jun 25 18:32:31.824492 Properties Len 12 Primary path
Jun 25 18:32:31.824505 SessionAttribute Len 24 Prio (5,0) flag 0x0 "TEST-MX960-MX104"
Jun 25 18:32:31.824520 Sender7 Len 12 10.198.123.205(port/lsp ID 1)
Jun 25 18:32:31.824546 Tspec Len 36 rate 100Mbps size 100Mbps peak Infbps m 20 M 1500
Jun 25 18:32:31.824560 ADspec Len 48 MTU 1500
Jun 25 18:32:31.824575 RecRoute Len 12 10.0.0.94

M120:

Jun 25 18:32:31.941242 RSVP recv Path 10.0.0.94->10.0.0.93 Len=272 ge-2/0/0.0 flags=0x1 ttl=255
Jun 25 18:32:31.941261 Integty Len 36 flag 0x0 key 0x00005e00000a seq 0xbf015059de530a00 digest 0x75c574bd 0x3c7e8ecb 0x435976f8 0x408b3263
Jun 25 18:32:31.941273 MessageID Len 12 Msg_ID: 878279 Epoch: 2641670 (Ack Desired)
Jun 25 18:32:31.941287 Session7 Len 16 10.198.123.100(port/tunnel ID 44394 Ext-ID 10.198.123.205) Proto 0
Jun 25 18:32:31.941299 Hop Len 12 10.0.0.94/0x80000009
Jun 25 18:32:31.941310 Time Len 8 30000 ms
Jun 25 18:32:31.941328 SrcRoute Len 28 10.0.0.93 S 10.0.0.41 S 10.0.0.170 S
Jun 25 18:32:31.941338 LabelRequest Len 8 EtherType 0x800
Jun 25 18:32:31.941349 Properties Len 12 Primary path
Jun 25 18:32:31.941359 SessionAttribute Len 24 Prio (5,0) flag 0x0 "TEST-MX960-MX104"
Jun 25 18:32:31.941372 Sender7 Len 12 10.198.123.205(port/lsp ID 1)
Jun 25 18:32:31.941393 Tspec Len 36 rate 100Mbps size 100Mbps peak Infbps m 20 M 1500
Jun 25 18:32:31.941405 ADspec Len 48 MTU 1500
Jun 25 18:32:31.941417 RecRoute Len 12 10.0.0.94

Jun 25 18:32:31.943251 RSVP send Path 10.198.123.205->10.198.123.100 Len=272 so-2/1/0.1 flags=0x1 ttl=254
Jun 25 18:32:31.943266 Integty Len 36 flag 0x0 key 0x00002a00000a seq 0xbf0150594b670e00 digest 0xc5bc0316 0x87716529 0xf2ca9320 0xd0fdd978
Jun 25 18:32:31.943277 MessageID Len 12 Msg_ID: 211 Epoch: 11650457 (Ack Desired)
Jun 25 18:32:31.943290 Session7 Len 16 10.198.123.100(port/tunnel ID 44394 Ext-ID 10.198.123.205) Proto 0
Jun 25 18:32:31.943303 Hop Len 12 10.0.0.42/0x80000003
Jun 25 18:32:31.943313 Time Len 8 30000 ms
Jun 25 18:32:31.943328 SrcRoute Len 20 10.0.0.41 S 10.0.0.170 S
Jun 25 18:32:31.943338 LabelRequest Len 8 EtherType 0x800
Jun 25 18:32:31.943349 Properties Len 12 Primary path
Jun 25 18:32:31.943359 SessionAttribute Len 24 Prio (5,0) flag 0x0 "TEST-MX960-MX104"
Jun 25 18:32:31.943372 Sender7 Len 12 10.198.123.205(port/lsp ID 1)
Jun 25 18:32:31.943390 Tspec Len 36 rate 100Mbps size 100Mbps peak Infbps m 20 M 1500
Jun 25 18:32:31.943402 ADspec Len 48 MTU 1500
Jun 25 18:32:31.943416 RecRoute Len 20 10.0.0.42 10.0.0.94

M320:

Jun 25 18:32:32.029412 RSVP recv Path 10.0.0.42->10.0.0.41 Len=272 so-0/3/0.1
Jun 25 18:32:32.029465 Integty Len 36 flag 0x0 key 0x00002a00000a seq 0xbf0150594b670e00 digest 0xc5bc0316 0x87716529 0xf2ca9320 0xd0fdd978
Jun 25 18:32:32.029477 MessageID Len 12 Msg_ID: 211 Epoch: 11650457 (Ack Desired)
Jun 25 18:32:32.029488 Session7 Len 16 10.198.123.100(port/tunnel ID 44394 Ext-ID 10.198.123.205) Proto 0
Jun 25 18:32:32.029498 Hop Len 12 10.0.0.42/0x80000003
Jun 25 18:32:32.029506 Time Len 8 30000 ms
Jun 25 18:32:32.029519 SrcRoute Len 20 10.0.0.41 S 10.0.0.170 S
Jun 25 18:32:32.029527 LabelRequest Len 8 EtherType 0x800
Jun 25 18:32:32.029537 Properties Len 12 Primary path
Jun 25 18:32:32.029547 SessionAttribute Len 24 Prio (5,0) flag 0x0 "TEST-MX960-MX104"
Jun 25 18:32:32.029556 Sender7 Len 12 10.198.123.205(port/lsp ID 1)
Jun 25 18:32:32.029580 Tspec Len 36 rate 100Mbps size 100Mbps peak Infbps m 20 M 1500
Jun 25 18:32:32.029590 ADspec Len 48 MTU 1500
Jun 25 18:32:32.029600 RecRoute Len 20 10.0.0.42 10.0.0.94

Jun 25 18:32:32.031527 RSVP send Path 10.198.123.205->10.198.123.100 Len=272 ge-1/3/3.0
Jun 25 18:32:32.031541 Integty Len 36 flag 0x0 key 0x0000a900000a seq 0xbf015059f47d0a00 digest 0xbb579467 0x457e455a 0x915f3fa4 0x6eeb2319
Jun 25 18:32:32.031550 MessageID Len 12 Msg_ID: 5484 Epoch: 8616743 (Ack Desired)
Jun 25 18:32:32.031560 Session7 Len 16 10.198.123.100(port/tunnel ID 44394 Ext-ID 10.198.123.205) Proto 0
Jun 25 18:32:32.031569 Hop Len 12 10.0.0.169/0x091a536c
Jun 25 18:32:32.031577 Time Len 8 30000 ms
Jun 25 18:32:32.031586 SrcRoute Len 12 10.0.0.170 S
Jun 25 18:32:32.031594 LabelRequest Len 8 EtherType 0x800
Jun 25 18:32:32.031603 Properties Len 12 Primary path
Jun 25 18:32:32.031652 SessionAttribute Len 24 Prio (5,0) flag 0x0 "TEST-MX960-MX104"
Jun 25 18:32:32.031662 Sender7 Len 12 10.198.123.205(port/lsp ID 1)
Jun 25 18:32:32.031676 Tspec Len 36 rate 100Mbps size 100Mbps peak Infbps m 20 M 1500
Jun 25 18:32:32.031686 ADspec Len 48 MTU 1500
Jun 25 18:32:32.031697 RecRoute Len 28 10.0.0.169 10.0.0.42 10.0.0.94

MX104:

Jun 25 18:32:32.149670 RSVP recv Path 10.0.0.169->10.0.0.170 Len=272 ge-0/0/1.0 flags=0x1 ttl=253
Jun 25 18:32:32.149787 Integty Len 36 flag 0x0 key 0x00000a0000a9 seq 0x595001bf000a7df4 digest 0x679457bb 0x5a457e45 0xa43f5f91 0x1923eb6e
Jun 25 18:32:32.149813 MessageID Len 12 Msg_ID: 5484 Epoch: 8616743 (Ack Desired)
Jun 25 18:32:32.149840 Session7 Len 16 10.198.123.100(port/tunnel ID 44394 Ext-ID 10.198.123.205) Proto 0
Jun 25 18:32:32.149867 Hop Len 12 10.0.0.169/0x091a536c
Jun 25 18:32:32.149891 Time Len 8 30000 ms
Jun 25 18:32:32.149918 SrcRoute Len 12 10.0.0.170 S
Jun 25 18:32:32.149943 LabelRequest Len 8 EtherType 0x800
Jun 25 18:32:32.149968 Properties Len 12 Primary path
Jun 25 18:32:32.149993 SessionAttribute Len 24 Prio (5,0) flag 0x0 "TEST-MX960-MX104"
Jun 25 18:32:32.150018 Sender7 Len 12 10.198.123.205(port/lsp ID 1)
Jun 25 18:32:32.150069 Tspec Len 36 rate 100Mbps size 100Mbps peak Infbps m 20 M 1500
Jun 25 18:32:32.150094 ADspec Len 48 MTU 1500
Jun 25 18:32:32.150121 RecRoute Len 28 10.0.0.169 10.0.0.42 10.0.0.94

RESV Messages

Once MX104 has received Path message, it will generate the RESV message containing the MPLS Label value towards its next-hop.

MX104:

Jun 25 18:32:32.151356 RSVP send Resv 10.0.0.170->10.0.0.169 Len=168 ge-0/0/1.0 flags=0x1 ttl=255
Jun 25 18:32:32.151402 Integty Len 36 flag 0x0 key 0x00000a0000aa seq 0x595001c00001e237 digest 0x2f64cc8a 0x402a4baf 0xbd34ce62 0x9436192e
Jun 25 18:32:32.151427 MessageID Len 12 Msg_ID: 1121 Epoch: 1236180 (Ack Desired)
Jun 25 18:32:32.151453 Session7 Len 16 10.198.123.100(port/tunnel ID 44394 Ext-ID 10.198.123.205) Proto 0
Jun 25 18:32:32.151479 Hop Len 12 10.0.0.170/0x091a536c
Jun 25 18:32:32.151503 Time Len 8 30000 ms
Jun 25 18:32:32.151527 Style Len 8 FF
Jun 25 18:32:32.151575 Flow Len 36 rate 100Mbps size 100Mbps peak Infbps m 20 M 1500
Jun 25 18:32:32.151600 Filter7 Len 12 10.198.123.205(port/lsp ID 1)
Jun 25 18:32:32.151624 Label Len 8 301456
Jun 25 18:32:32.151650 RecRoute Len 12 10.0.0.170

M320:

Jun 25 18:32:32.235459 RSVP recv Resv 10.0.0.170->10.0.0.169 Len=168 ge-1/3/3.0
Jun 25 18:32:32.235476 Integty Len 36 flag 0x0 key 0x0000aa00000a seq 0xc001505937e20100 digest 0x8acc642f 0xaf4b2a40 0x62ce34bd 0x2e193694
Jun 25 18:32:32.235486 MessageID Len 12 Msg_ID: 1121 Epoch: 1236180 (Ack Desired)
Jun 25 18:32:32.235496 Session7 Len 16 10.198.123.100(port/tunnel ID 44394 Ext-ID 10.198.123.205) Proto 0
Jun 25 18:32:32.235506 Hop Len 12 10.0.0.170/0x091a536c
Jun 25 18:32:32.235514 Time Len 8 30000 ms
Jun 25 18:32:32.235523 Style Len 8 FF
Jun 25 18:32:32.235537 Flow Len 36 rate 100Mbps size 100Mbps peak Infbps m 20 M 1500
Jun 25 18:32:32.235547 Filter7 Len 12 10.198.123.205(port/lsp ID 1)
Jun 25 18:32:32.235556 Label Len 8 301456
Jun 25 18:32:32.235565 RecRoute Len 12 10.0.0.170
Jun 25 18:32:32.235669 RSVP new resv state, session 10.198.123.100(port/tunnel ID 44394 Ext-ID 10.198.123.205) Proto 0

Jun 25 18:32:32.240512 RSVP send Resv 10.0.0.41->10.0.0.42 Len=176 so-0/3/0.1
Jun 25 18:32:32.240530 Integty Len 36 flag 0x0 key 0x00002900000a seq 0xbf01505945ae0d00 digest 0xa61d34f1 0x42d26c8a 0x33b66d12 0xdd26b232
Jun 25 18:32:32.240540 MessageID Len 12 Msg_ID: 5485 Epoch: 8616743 (Ack Desired)
Jun 25 18:32:32.240551 Session7 Len 16 10.198.123.100(port/tunnel ID 44394 Ext-ID 10.198.123.205) Proto 0
Jun 25 18:32:32.240561 Hop Len 12 10.0.0.41/0x80000003
Jun 25 18:32:32.240569 Time Len 8 30000 ms
Jun 25 18:32:32.240577 Style Len 8 FF
Jun 25 18:32:32.240598 Flow Len 36 rate 100Mbps size 100Mbps peak Infbps m 20 M 1500
Jun 25 18:32:32.240608 Filter7 Len 12 10.198.123.205(port/lsp ID 1)
Jun 25 18:32:32.240617 Label Len 8 315600
Jun 25 18:32:32.240629 RecRoute Len 20 10.0.0.41 10.0.0.170

M120:

Jun 25 18:32:32.357134 RSVP recv Resv 10.0.0.41->10.0.0.42 Len=176 so-2/1/0.1 flags=0x1 ttl=255
Jun 25 18:32:32.357151 Integty Len 36 flag 0x0 key 0x00002900000a seq 0xbf01505945ae0d00 digest 0xa61d34f1 0x42d26c8a 0x33b66d12 0xdd26b232
Jun 25 18:32:32.357162 MessageID Len 12 Msg_ID: 5485 Epoch: 8616743 (Ack Desired)
Jun 25 18:32:32.357177 Session7 Len 16 10.198.123.100(port/tunnel ID 44394 Ext-ID 10.198.123.205) Proto 0
Jun 25 18:32:32.357190 Hop Len 12 10.0.0.41/0x80000003
Jun 25 18:32:32.357200 Time Len 8 30000 ms
Jun 25 18:32:32.357210 Style Len 8 FF
Jun 25 18:32:32.357235 Flow Len 36 rate 100Mbps size 100Mbps peak Infbps m 20 M 1500
Jun 25 18:32:32.357249 Filter7 Len 12 10.198.123.205(port/lsp ID 1)
Jun 25 18:32:32.357259 Label Len 8 315600
Jun 25 18:32:32.357274 RecRoute Len 20 10.0.0.41 10.0.0.170

Jun 25 18:32:32.379175 RSVP send Resv 10.0.0.93->10.0.0.94 Len=184 ge-2/0/0.0 flags=0x1 ttl=255
Jun 25 18:32:32.379194 Integty Len 36 flag 0x0 key 0x00005d00000a seq 0xc0015059ddcb0500 digest 0x123882a6 0xc852ee76 0x2564233e 0x68cb222c
Jun 25 18:32:32.379206 MessageID Len 12 Msg_ID: 212 Epoch: 11650457 (Ack Desired)
Jun 25 18:32:32.379220 Session7 Len 16 10.198.123.100(port/tunnel ID 44394 Ext-ID 10.198.123.205) Proto 0
Jun 25 18:32:32.379233 Hop Len 12 10.0.0.93/0x80000009
Jun 25 18:32:32.379244 Time Len 8 30000 ms
Jun 25 18:32:32.379253 Style Len 8 FF
Jun 25 18:32:32.379281 Flow Len 36 rate 100Mbps size 100Mbps peak Infbps m 20 M 1500
Jun 25 18:32:32.379326 Filter7 Len 12 10.198.123.205(port/lsp ID 1)
Jun 25 18:32:32.379338 Label Len 8 301728
Jun 25 18:32:32.379356 RecRoute Len 28 10.0.0.93 10.0.0.41 10.0.0.170

MX960:

Jun 25 18:32:32.465718 RSVP recv Resv 10.0.0.93->10.0.0.94 Len=184 ge-1/1/7.0 flags=0x1 ttl=255
Jun 25 18:32:32.465736 Integty Len 36 flag 0x0 key 0x00005d00000a seq 0xc0015059ddcb0500 digest 0x123882a6 0xc852ee76 0x2564233e 0x68cb222c
Jun 25 18:32:32.465750 MessageID Len 12 Msg_ID: 212 Epoch: 11650457 (Ack Desired)
Jun 25 18:32:32.465767 Session7 Len 16 10.198.123.100(port/tunnel ID 44394 Ext-ID 10.198.123.205) Proto 0
Jun 25 18:32:32.465785 Hop Len 12 10.0.0.93/0x80000009
Jun 25 18:32:32.465798 Time Len 8 30000 ms
Jun 25 18:32:32.465811 Style Len 8 FF
Jun 25 18:32:32.465841 Flow Len 36 rate 100Mbps size 100Mbps peak Infbps m 20 M 1500
Jun 25 18:32:32.465856 Filter7 Len 12 10.198.123.205(port/lsp ID 1)
Jun 25 18:32:32.465869 Label Len 8 301728
Jun 25 18:32:32.465890 RecRoute Len 28 10.0.0.93 10.0.0.41 10.0.0.170

re1.bentley> show rsvp session name TEST-MX960-MX104 detail
Ingress RSVP: 30 sessions
10.198.123.100
 From: 10.198.123.205, LSPstate: Up, ActiveRoute: 0
 LSPname: TEST-MX960-MX104, LSPpath: Primary
 LSPtype: Static Configured
 Suggested label received: -, Suggested label sent: -
 Recovery label received: -, Recovery label sent: 301728
 Resv style: 1 FF, Label in: -, Label out: 301728
 Time left: -, Since: Sun Jun 25 18:32:31 2017
 Tspec: rate 100Mbps size 100Mbps peak Infbps m 20 M 1500
 Port number: sender 1 receiver 44394 protocol 0
 PATH rcvfrom: localclient
 Adspec: sent MTU 1500
 Path MTU: received 1500
 PATH sentto: 10.0.0.93 (ge-1/1/7.0) 3 pkts
 RESV rcvfrom: 10.0.0.93 (ge-1/1/7.0) 1 pkts, Entropy label: No
 Explct route: 10.0.0.93 10.0.0.41 10.0.0.170
 Record route: <self> 10.0.0.93 10.0.0.41 10.0.0.170
Total 1 displayed, Up 1, Down 0

As this service was part of L2VPN CCC configuration, hence no explicit null label was sent by penultimate hop router resulting in label sent to MX960 PE.

xe-2/0/0.601 (1 entry, 1 announced)

TSI:

KRT in-kernel xe-2/0/0.601.0 /32 -> {Push 301728}

*CCC Preference: 200/1

Next hop type: Router, Next hop index: 1255

Address: 0xa5dba0c

Next-hop reference count: 2

Next hop: 10.0.0.93 via ge-1/1/7.0 weight 0x1, selected

Label-switched-path TEST-MX960-MX104

Label operation: Push 301728

Label TTL action: no-prop-ttl

Load balance label: Label 301728: None;

Label element ptr: 0xa7cc2c0

Label parent element ptr: 0x0

Label element references: 3

Label element child references: 0

Label element lsp id: 0

Session Id: 0xbcf

State: <Active Int>

Local AS: 65004

Age: 10:45 Metric: 425

Validation State: unverified

Task: MPLS global

Announcement bits (1): 1-KRT

AS path: I

So that’s all for RSVP in Junos. I hope you liked the blog and let me know if there are any queries.

Mohit Mittal

vrf-table-label on Juniper JunOS

16 Jun 2017BGP, Cisco, Juniper, Junos, MPLS, NetworkingBGP, Cisco, Juniper, Junos, L3VPN, MPLS, MVPN, Networking, tunnel-pic, vrf, vrf-table-labelMohit

In this blog we will discuss about one important knob in JunOS i.e vrf-table-label.

Vrf-table-label is useful for 2 purposes in Junos

Save label space
Perform 2 lookup on packet

So let’s understand it more. We will start with 1^st point above

Junos by default allocates same VPN Label to prefixes recieved from one CE Interface. So for example if you have 2 CEs connected via 2 different interfaces and they are in same VPN on PE then Junos will allocate 2 different VPN labels to the prefixes recieved. In Cisco this is different where VPN label is allocated on per prefix which according to some is not optimal but we are not comparing anything here.

Currently in our configuration vrf-table-label is not configured. If you see below, we have 2 CEs connected to Juniper M320 PE1 via 2 different interfaces and we have Ebgp relationship between them and we are receiving some routes over it.

PE1-re1> show route 10.203.20.6
MVPN-1.inet.0: 46 destinations, 77 routes (46 active, 0 holddown, 0 hidden)
Restart Complete
+ = Active Route, – = Last Active, * = Both

10.203.20.4/30 *[Direct/0] 3d 00:21:55
> via ge-0/3/2.20

PE1-re1> show route 10.203.12.2
MVPN-1.inet.0: 46 destinations, 77 routes (46 active, 0 holddown, 0 hidden)
Restart Complete
+ = Active Route, – = Last Active, * = Both

10.203.12.0/30 *[Direct/0] 00:10:26
> via so-1/0/0.12

PE1-re1> show route receive-protocol bgp 10.203.12.2 table MVPN-1.inet.0
MVPN-1.inet.0: 46 destinations, 77 routes (46 active, 0 holddown, 0 hidden)
Restart Complete
Prefix Nexthop MED Lclpref AS path
* 10.1.225.128/32 10.203.12.2 65012 I
10.203.12.0/30 10.203.12.2 65012 I

PE1-re1> show route receive-protocol bgp 10.203.20.6 table MVPN-1.inet.0
MVPN-1.inet.0: 46 destinations, 77 routes (46 active, 0 holddown, 0 hidden)
Restart Complete
Prefix Nexthop MED Lclpref AS path
* 10.0.233.0/30 10.203.20.6 65020 I

Now if we look at the VPN label which is being tagged by this PE1 for the routes received by CE, we can see that Junos is allocating separate VPN Labels to both of the routes which is what I mentioned earlier.

PE1-re1> show route advertising-protocol bgp 10.198.123.236 10.0.233.0/30 extensive
MVPN-1.inet.0: 46 destinations, 77 routes (46 active, 0 holddown, 0 hidden)
Restart Complete
* 10.0.233.0/30 (2 entries, 1 announced)
BGP group mvpn-rr type Internal
Route Distinguisher: 10.198.123.203:32764
VPN Label: 300448
Nexthop: Self
Flags: Nexthop Change
Localpref: 100
AS path: [65004] 65020 I
Communities: target:65000:321 src-as:65004:0 rt-import:10.198.123.203:16

PE1-re1> show route advertising-protocol bgp 10.198.123.236 10.203.12.0/30 extensive
MVPN-1.inet.0: 46 destinations, 77 routes (46 active, 0 holddown, 0 hidden)
Restart Complete
* 10.203.12.0/30 (2 entries, 1 announced)
BGP group mvpn-rr type Internal
Route Distinguisher: 10.198.123.203:32764
VPN Label: 300480
Nexthop: Self
Flags: Nexthop Change
Localpref: 100
AS path: [65004] I
Communities: target:65000:321 src-as:65004:0 rt-import:10.198.123.203:16

Now if we configure the vrf-table-label under routing instance on PE1, we can see the difference.

[edit routing-instances MVPN-1]
PE1-re1# set vrf-table-label

edit routing-instances MVPN-1]
PE1-re1# commit
re1:
configuration check succeeds
re0:
commit complete
re1:
commit complete

See the difference below, now only one VPN label is being allocated for the whole VRF and this really saves the label space.

PE1-re1> show route advertising-protocol bgp 10.198.123.236 10.203.12.0/30 extensive
MVPN-1.inet.0: 46 destinations, 77 routes (46 active, 0 holddown, 0 hidden)
Restart Complete
* 10.203.12.0/30 (2 entries, 1 announced)
BGP group mvpn-rr type Internal
Route Distinguisher: 10.198.123.203:32764
VPN Label: 39
Nexthop: Self
Flags: Nexthop Change
Localpref: 100
AS path: [65004] I
Communities: target:65000:321 src-as:65004:0 rt-import:10.198.123.203:16

PE1-re1> show route advertising-protocol bgp 10.198.123.236 10.0.233.0/30 extensive
MVPN-1.inet.0: 46 destinations, 77 routes (46 active, 0 holddown, 0 hidden)
Restart Complete
* 10.0.233.0/30 (2 entries, 1 announced)
BGP group mvpn-rr type Internal
Route Distinguisher: 10.198.123.203:32764
VPN Label: 39
Nexthop: Self
Flags: Nexthop Change
Localpref: 100
AS path: [65004] 65020 I
Communities: target:65000:321 src-as:65004:0 rt-import:10.198.123.203:16

So this completes one part. Now moving over to 2nd part.
Junos by default looks at the incoming MPLS packet, Pops the label and sends the underlying packet to CE without looking at IP packet at all. This situation is fine in case you have PE connected to CE via P2P links like Serial links however if you have Broadcast medium like Ethernet in between then router can’t just send the packet like this without first building the frame and to build frame it needs to do ARP lookup to get the MAC Address of the CE. So it needs to do extra lookup apart from MPLS lookup.
Vrf-table-label actually allows the router to do 2 lookups. The first lookup is done on the VPN label to determine which VRF table to refer to, and the second lookup is done on the IP header to determine how to forward packets to the correct end hosts on the shared medium. This can be useful for number of applications like ingress firewall filters, CoS etc. Now a days VT interface (tunnel-pic) is also used to do the same however if router doesn’t support tunnel-pic then vrf-table-label can be used in its place to do the same thing. With VTL, lsi interface is created which allows it to handle the first lookup before a second ARP/IP lookup is carried out through the PFE.

Lets rollback the changes we did above and come back to same situation where unique label is assigned per CE port.

VPN Label 300560 is assigned for the route by PE1 and when mpls table is checked for that particular label we can see action is Pop plus to send the packet directly to interface.

PE1-re1> show route advertising-protocol bgp 10.198.123.236 10.203.12.0/30 extensive
MVPN-1.inet.0: 46 destinations, 77 routes (46 active, 0 holddown, 0 hidden)
Restart Complete
* 10.203.12.0/30 (2 entries, 1 announced)
BGP group mvpn-rr type Internal
Route Distinguisher: 10.198.123.203:32764
VPN Label: 300560
Nexthop: Self
Flags: Nexthop Change
Localpref: 100
AS path: [65004] I
Communities: target:65000:321 src-as:65004:0 rt-import:10.198.123.203:16

PE1-re1> show route table mpls.0 label 300560
mpls.0: 57 destinations, 57 routes (57 active, 0 holddown, 0 hidden)
Restart Complete
+ = Active Route, – = Last Active, * = Both
300560 *[VPN/170] 00:00:41
> via so-1/0/0.12, Pop

If we enable the vrf-table-label now and check the same route and corresponding label. Lets see what we see.

PE1-re1> show route advertising-protocol bgp 10.198.123.236 10.203.12.0/30 extensive
MVPN-1.inet.0: 46 destinations, 77 routes (46 active, 0 holddown, 0 hidden)
Restart Complete
* 10.203.12.0/30 (2 entries, 1 announced)
BGP group mvpn-rr type Internal
Route Distinguisher: 10.198.123.203:32764
VPN Label: 40
Nexthop: Self
Flags: Nexthop Change
Localpref: 100
AS path: [65004] I
Communities: target:65000:321 src-as:65004:0 rt-import:10.198.123.203:16

PE1-re1> show route table mpls.0 label 40
mpls.0: 53 destinations, 53 routes (53 active, 0 holddown, 0 hidden)
Restart Complete
+ = Active Route, – = Last Active, * = Both

40 *[VPN/0] 00:00:12
to table MVPN-1.inet.0, Pop

So we can see, label 40 is basically pointing to routing-table now and not to interface as in our previous case. You can see the corresponding LSI interface allocated by looking at following command

PE1-re1> show route instance MVPN-1 detail
MVPN-1:
Router ID: 10.14.233.1
Type: vrf State: Active
Restart State: Complete Path selection timeout: 300
Interfaces:
lsi.24
so-1/0/0.12
ge-0/3/3.50
ge-0/3/2.20
vt-1/2/0.20
Route-distinguisher: 10.198.123.203:32764
Vrf-import: [ __vrf-import-MVPN-1-internal__ ]
Vrf-export: [ __vrf-export-MVPN-1-internal__ ]
Vrf-import-target: [ target:65000:321 ]
Vrf-export-target: [ target:65000:321 ]
Fast-reroute-priority: low
Tables:
MVPN-1.inet.0 : 77 routes (46 active, 0 holddown, 0 hidden)
Restart Complete
MVPN-1.inet.1 : 11 routes (9 active, 0 holddown, 0 hidden)
Restart Complete
MVPN-1.mvpn.0 : 77 routes (42 active, 7 holddown, 0 hidden)
Restart Complete

Ok so that’s all. I hope you liked the blog and I was able to resolve some of your confusion on this command. If you still have any queries, please let me know and I would be happy to discuss.

Regards
Mohit Mittal

DHCP Server on Juniper MX104

2 Jun 2017Alcatel, Cisco, Juniper, Junos, NetworkingAlcatel, Cisco, DHCP, Juniper, Junos, Networking, TCP/IPMohit

In this blog, we will discuss about configuration of DHCP for IPv4 on Junos particularly for MX104. MX router will act as a DHCP Local server which will assign IP Addresses to clients from the DHCP pool configured.

To configure DHCP as local server we need to apply the following license on MX which is paid license over the top.

subscriber-address-assignment – Radius/SRC Address Pool Assignment

subscriber-ip – Dynamic and Static IP

For those who doesn’t want to buy license, they have option of configuring the DHCP as relay however for which server will be external and not internal.

With this blog, we will look at configuration of router acting as DHCP server. Relay configuration is not part of this current blog.

Below model topology will be used where clients (Windows Laptop) is connected to MX104 PE via switch. VRRP is configured with MX104 CE-1 and MX104 CE-2 and both are acting as DHCP Server, however we will be looking at configuration of MX104 CE-1 as same configuration needs to be configured on both.

MX104 PE is connected to MX960 PE over L2VPN which is just extending the L2 domain from client over to DHCP server.

Ok Lets start by looking at Interface configuration on MX104-CE-1 where xe-2/0/3 link is connected to EX4550 switch and VRRP is running with VRRP VIP as 50.50.50.1 and address on logical interface is 50.50.50.101.

Nothing special till here and no DHCP configuration even.

MX104-CE-1> show configuration logical-systems LS2-CLMB interfaces xe-2/0/3
unit 601 {
 vlan-id 601;
 family inet {
 address 50.50.50.101/24 {
 vrrp-group 201 {
 virtual-address 50.50.50.1;
 priority 200;
 accept-data;
 track {
 route 0.0.0.0/0 routing-instance default priority-cost 101;
 }
 }
 }
 }
}

Ok now lets add DHCP configuration by defining the dhcp-local server under system services hierarchy.

Here we need to define the group with any arbitrary name and interface which will be participating in DHCP msg exchange.

system {
 services {
 dhcp-local-server {
 group dhcp {
 interface xe-2/0/3.601;
 }
 }
 }
}

Once dhcp server has been defined, we will configure DHCP pools to provide addresses to clients.

In same heirachy we can define the dhcp-attributes like lease time, DNS servers and router which suggests the ip address of router in the subnetwork. We have 2 routers providing the DHCP services however as its under VRRP it will be better to give just one address which will be VRRP VIP. In this way in case of any issues on CE-1, VIP will move over to CE-2 and it will be able to assign the addresses.

Range is defined as ip addresses which DHCP server will assign. Lease time is 24 hours in seconds i.e 86400

access {
 address-assignment {
 pool dhcp {
 family inet {
 network 50.50.50.0/24;
 range dhcp {
 low 50.50.50.4;
 high 50.50.50.100;
 }
 dhcp-attributes {
 maximum-lease-time 86400;
 name-server {
 8.8.8.8;
 }
 router {
 50.50.50.1;
 }
 }
 }
 }
 }
}

Once everything is done, as soon as Laptop comes online it will send the request and MX104 will assign the ip address. We will see the messages in just a while but one thing to note is that if you have protect-RE firewall filter configured on loopback0 interface of MX104, it is essential to allow bootps and bootpc messages

term dhcp {
from {
 protocol udp;
 port [ bootpc bootps ];
}
then accept;
}

MX104_CE-1> show dhcp server binding logical-system LS2-CLMB
IP address Session Id Hardware address  Expires State Interface
50.50.50.5 2          68:f7:28:45:14:91 85495   BOUND xe-2/0/3.601

As you can see above, 50.50.50.5 address has been assigned by MX104 and state is BOUND and also listing the hardware address of client machine.

Now lets see how DHCP messages flow. I have shown below the snapshots of wireshark capture for the DHCP messages.

As soon as Laptop comes online or it is connected to LAN, first message it sent is DHCP discover message which is basically a broadcast BOOTP message with frame field as its own mac address as source and all FFs as destination MAC. UDP port number is 68 with destination as 67 so it is basically looks like

UDP 0.0.0.0:68 -> 255.255.255.255:67

As client doesn’t have IP address at this time, it uses 0.0.0.0 as src ip.

68 is standard UDP port assigned for bootp client and 67 for bootp server.

Once client broadcasts the DHCP discover request, DHCP server sends a DHCP Offer. Src IP Address is physical IP of router which is currently holding the VIP in VRRP case. In our case its MX104 CE-1.

Offer will contain the IP Address 50.50.50.5 as we have already seen in CLI output above along with other parameters which we configured like Lease time, Subnet Mask, Router address, DNS Server etc etc.

After receiving the Offer and before accepting it, client again sends the broadcast message by including the IP 50.50.50.5 for confirmation.

At this point, DHCP server sends unicast acknowledgment for it to keep the address and connection is complete.

DHCP Client will periodically sends DHCP Inform messages (both Unicast and Broadcast) to let others know of the address being used.

Ok so that’s all for DHCP, i hope you liked the post and let me know if you have any feedback or queries.

Mohit Mittal