Category Archives: IOS-XR

vSONIC Virtual Switch on EVE-NG

SONiC is an open source network operating system based on Linux that runs on switches from multiple vendors and ASICs. SONiC offers a full-suite of network functionality, like BGP and OSPF, VXLAN that has been production-hardened in the data centers of some of the largest cloud-service providers.

The community around SONiC has been growing and includes Juniper including Apstra, Arista, Nokia, Alibaba, Comcast, Cisco, Broadcom, Nvidia-Mellanox and VMware. SONiC underpins Microsoft’s Azure networking services. According to IDC, a SONiC data-center switch market will be worth $2 billion by 2024.

Some term it as ‘Linux of Networking’.

In this blog, we will see how to spin up a sample topology using vSONIC Virtual Switch on EVE-NG.

To start with, we will use mssonic.yml file which lists the generic parameters for spinning up the instance.

  1. Copy mssonic.yml file into “/opt/unetlab/html/templates/intel” or “/opt/unetlab/html/templates/amd” based on your cpu. In my case, I am using EVE-NG on macbook so I have used Intel.

root@eve-ng:~# ls -l /opt/unetlab/html/templates/intel/ | grep mssonic

-rw-r–r– 1 root root 1993 Jul 30 22:41 mssonic.yml


2. Create a folder under “opt/unetlab/addons/qemu/” with name “mssonic-version/” like “mssonic-3.1.2”.

Keyword “mssonic” is important as using this only, eve-ng will recognize this image.

root@eve-ng:~# ls -l /opt/unetlab/addons/qemu/ | grep ms

drwxr-xr-x 2 root root 4096 Jul 30 22:48 mssonic-3.1.2


3. Gunzip the .gz file to extract the image file.

root@eve-ng:/opt/unetlab/addons/qemu/mssonic-3.1.2# gunzip sonic-vs-3.1.2.img.gz

root@eve-ng:/opt/unetlab/addons/qemu/mssonic-3.1.2# ls -l

total 2380932

-rw-r–r– 1 root root 2438070272 Jul 30 22:55 sonic-vs-3.1.2.img

4. Rename sonic-vs-3.1.2.img to virtioa.qcow2. Please make sure to rename only and don’t convert it.

root@eve-ng:/opt/unetlab/addons/qemu/mssonic-3.1.2# mv sonic-vs-3.1.2.img virtioa.qcow2

root@eve-ng:/opt/unetlab/addons/qemu/mssonic-3.1.2# ls -l

total 2380932

-rw-r–r– 1 root root 2438070272 Jul 30 22:58 virtioa.qcow2

5. Fix the permissions as usual on eve-ng.

root@eve-ng:/opt/unetlab/addons/qemu/mssonic-3.1.2# /opt/unetlab/wrappers/unl_wrapper -a fixpermissions


Now we all set to use this under EVE-NG

I have made a simple leaf-spine topology using Sonic Virtual Switches

6. Open the Eve-NG UI.

Add the new Node, and select Sonic Router as below.

7. Change any settings here if you need however defaults should be good.

8. I have built a simple Leaf-Spine topology using 4 Sonic VS.

9. Start one or more Switches and let it boot.


Connected to

Escape character is ‘^]’.

Jul 31 15:30:59.295935 2021 sonic INFO sonic-ztp[3850]: ZTP service started.

Jul 31 15:30:59.295971 2021 sonic INFO sonic-ztp[3850]: Failed to set system MAC address as the random number generator seed input.

Jul 31 15:30:59.295999 2021 sonic INFO sonic-ztp[3850]: Checking running configuration to load ZTP configuration profile.

Jul 31 15:30:59.893505 2021 sonic INFO sonic-ztp[3845]: Waiting for system online status before continuing ZTP. (This may take 30–120 seconds).

Debian GNU/Linux 9 sonic ttyS0

Jul 31 15:31:34.932822 System is ready

Jul 31 15:31:36.290136 2021 sonic INFO sonic-ztp[3845]: System is ready to respond.

Jul 31 15:31:36.308466 2021 sonic INFO sonic-ztp[3850]: Link up detected for interface Ethernet0

Jul 31 15:31:36.308525 2021 sonic INFO sonic-ztp[3850]: Link up detected for interface Ethernet1

Jul 31 15:31:36.308554 2021 sonic INFO sonic-ztp[3850]: Link up detected for interface Ethernet2

Jul 31 15:31:36.308581 2021 sonic INFO sonic-ztp[3850]: Link up detected for interface Ethernet3

Jul 31 15:31:36.308609 2021 sonic INFO sonic-ztp[3850]: Link up detected for interface Ethernet4

Jul 31 15:31:36.308637 2021 sonic INFO sonic-ztp[3850]: Link up detected for interface Ethernet5

Jul 31 15:31:36.308664 2021 sonic INFO sonic-ztp[3850]: Link up detected for interface Ethernet6

Jul 31 15:31:36.308741 2021 sonic INFO sonic-ztp[3850]: Link up detected for interface Ethernet7

Jul 31 15:31:36.308769 2021 sonic INFO sonic-ztp[3850]: Link up detected for interface Ethernet8

Jul 31 15:31:36.308821 2021 sonic INFO sonic-ztp[3850]: Link up detected for interface Ethernet9

Jul 31 15:31:36.308850 2021 sonic INFO sonic-ztp[3850]: Link up detected for interface Ethernet10

Jul 31 15:31:36.309163 2021 sonic INFO sonic-ztp[3850]: Link up detected for interface Ethernet11

Jul 31 15:31:36.340452 2021 sonic INFO sonic-ztp[3850]: Link up detected for interface Ethernet12

Jul 31 15:31:36.340489 2021 sonic INFO sonic-ztp[3850]: Link up detected for interface Ethernet13

Jul 31 15:31:36.340761 2021 sonic INFO sonic-ztp[3850]: Link up detected for interface Ethernet14

Default username/pwd – admin/YourPaSsWoRd

10. Once up and running, you would see lots of ztp related messages which can be disabled using below command.

sudo config ztp disable

sudo config save -y

11. Once done, you can go into sonic cli, using sonic-cli

admin@sonic:~$ sonic-cli



sonic# ?

  clear        Clear commands

  configure    Enter configuration mode

  copy         Perform file copy operations

  exit         Exit from the CLI

  fast-reboot  fast-reboot [options] (-h shows help)

  image        Image related commands

  logger       Enter messages into the system log

  no           No commands under Exec mode

  ping         Send ICMP ECHO_REQUEST to network hosts

  ping6        Send ICMPv6 ECHO_REQUEST to network hosts

  reboot       reboot [options] (-h shows help)

  renew        Renew commands

  show         Show running system information

  terminal     Set terminal settings

  tpcm         SONiC image installation manager

  traceroute   Print the route packets take to the host

  traceroute6  Print the route packets take to the IPv6 host

  warm-reboot  warm-reboot [options] (-h shows help)

  write        Save config


to prove its working, lets configure IP Addresses on Interfaces and see if we can ping each other.

On Leaf-1:

sonic(config)# hostname leaf-1





leaf-1# show running-configuration interface Ethernet 0


interface Ethernet0

 mtu 9100

 speed 25000

 fec none

 no shutdown

 ip address


On Spine-1:

spine-1# show running-configuration interface Ethernet0


interface Ethernet0

 mtu 9100

 speed 25000

 fec none

 no shutdown

 ip address


12. Ping the other end to find everything is working

spine-1# ping

PING ( 56(84) bytes of data.

64 bytes from icmp_seq=1 ttl=64 time=5.32 ms

64 bytes from icmp_seq=2 ttl=64 time=1.34 ms


— ping statistics —

2 packets transmitted, 2 received, 0% packet loss, time 1001ms

rtt min/avg/max/mdev = 1.349/3.336/5.323/1.987 ms


That’s all, hope you like it.. In next sessions, we can go through some more specific scenarios around it.


Segment Routed L2VPN TE – Cisco IOS-XR

Hi All

Let’s see Segment routing in action in this blog particularly on IOS-XR. Segment routing is quite new concept which is picking pace these days. In my earlier blog I listed the differences between Segment routing and RSVP-TE and SR can replace it and there are certain areas where it may not be able to help however L3VPN and L2VPN Traffic Engineering is surely one area where it can be used and in this blog we will use SR as TE while configuring the L2VPN.

For this we will take NCS5508 as our router platform in below topology where we will configure the L2VPN SR-TE between NCS5508-1 to NCS5508-3 via NCS5508-8.

Segment Routing in IOS-XR


Let’s see the SR config first.

SR beauty is that there is no special protocol needed to run it. SR Labels will be advertised in OSPF/ISIS and these protocols have been uplifted to carry them. SR Labels are carried in Type 10 Opaque area LSA as TLV.

If you are familiar with OSPF config in IOS-XR, most of the config below looks similar to you as we have just enabled OSPF under area0 and added interfaces under it.

However there are 3 configs highlighted in RED which we have enabled for Segment routing.

RP/0/RP0/CPU0:ncs5508-1#show running-config router ospf
router ospf 1
 distribute link-state
 segment-routing mpls
 nsf ietf
 segment-routing sr-prefer
 area 0
 mpls traffic-eng
 interface Loopback0
 passive enable
 prefix-sid index 1 explicit-null
 interface HundredGigE0/1/0/0
 cost 1
 network point-to-point
 interface FortyGigE0/2/0/8
 cost 4
 network point-to-point
 interface FortyGigE0/2/0/10
 cost 4
 network point-to-point
 interface FortyGigE0/2/0/18
 cost 4
 network point-to-point
 mpls traffic-eng router-id Loopback0

segment-routing mpls , this command causes OSPF to originate RI LSA, Extended Prefix and Extended Link LSAs. It enables MPLS on all interfaces in area(s) enabled for SR and programs SR MPLS labels for forwarding.

segment-routing sr-prefer is used to set the preference of segment routing (SR) labels over label distribution protocol (LDP) labels in case both are available towards destination in your network.

prefix-sid index 1 explicit-null — A prefix SID is associated with an IP prefix. The prefix SID is manually configured from the segment routing global block (SRGB) range of labels. The prefix segment steers the traffic along the shortest path to its destination. A node SID is a special type of prefix SID that identifies a specific node. It is configured under the loopback interface with the loopback address of the node as the prefix. The prefix SID is globally unique within the segment routing domain.

Let’s verify it

RP/0/RP0/CPU0:ncs5508-1#show ospf sid-database
SID Database for ospf 1 with ID

SID Prefix/Mask
-------- ------------------
1 (L)

In the same way we have configured the Node-SID as same index as last octet on lo0 interface.

RP/0/RP0/CPU0:ncs5508-1#show ospf database opaque-area
 OSPF Router with ID ( (Process ID 1)
Type-10 Opaque Link Area Link States (Area 0)
LS age: 782
 Options: (No TOS-capability, DC)
 LS Type: Opaque Area Link
 Link State ID:
 Opaque Type: 7
 Opaque ID: 1
 Advertising Router:
 LS Seq Number: 800006fa
 Checksum: 0xed8b
 Length: 44
Extended Prefix TLV: Length: 20
 Route-type: 1
 AF : 0
 Flags : 0x40
 Prefix :
SID sub-TLV: Length: 8
 Flags : 0x50
 MTID : 0
 Algo : 0
 SID Index : 1
RP/0/RP0/CPU0:ncs5508-1#show mpls forwarding
Local  Outgoing    Prefix             Outgoing     Next Hop        Bytes
Label  Label       or ID              Interface                    Switched

—— ———– —————— ———— ————— ————

16002  Exp-Null-v4 SR Pfx (idx 2)     Hu0/1/0/0     0
16003  16003       SR Pfx (idx 3)     Hu0/1/0/0     0
16004  Exp-Null-v4 SR Pfx (idx 4)     Fo0/2/0/8     0
16005  16005       SR Pfx (idx 5)     Fo0/2/0/8     6421133
16006  16006       SR Pfx (idx 6)     Hu0/1/0/0     0
       16006       SR Pfx (idx 6)     Fo0/2/0/8     0
16007  16007       SR Pfx (idx 7)     Hu0/1/0/0     0
16008  Exp-Null-v4 SR Pfx (idx 8)     Fo0/2/0/18     0

Now let’s create a Segment routed TE EVPN based P2P L2 Circuit. 🙂

Ideally we know that Controller is needed to play with Segment routed labels and Controller can insert the appropriate labels required for TE however if you don’t have Controller, you can configure the path by explicitly giving the path through which traffic will be going.

So we will start with l2vpn xconnect taking edge interface on NCS5508-1 and assigning a EVPN EVI 1100 with source and target ac-id (attachment circuit id) and associate it with pw-class which we will define in next step.


RP/0/RP0/CPU0:ncs5508-1#show running-config l2vpn xconnect group evpn-vpws p2p vpws1
 xconnect group evpn-vpws
 p2p vpws1
 interface HundredGigE0/2/0/2.1100
 neighbor evpn evi 1100 target 11003 source 11001
 pw-class vpws1-class

Pw-class is associated with sr-te policy to steer traffic through the network. An SR-TE policy path is expressed as a list of segments that specifies the path, called a segment ID (SID) list. Each segment is an end-to-end path from the source to the destination, and instructs the routers in the network to follow the specified path instead of the shortest path calculated by the IGP

RP/0/RP0/CPU0:ncs5508-1#show running-config l2vpn pw-class vpws1-class
 pw-class vpws1-class
 encapsulation mpls
 preferred-path sr-te policy vpws1-policy
RP/0/RP0/CPU0:ncs5508-1#show running-config segment-routing traffic-eng policy vpws1-policy
 policy vpws1-policy
 color 10 end-point ipv4
 preference 200
 type te
 preference 300
 explicit segment-list vpws1-path

So in our policy, we have defined one preferred path which is dynamic and if that fails it should failover to explicitly configured segment list defined via path vpws1-path.

RP/0/RP0/CPU0:ncs5508-1#show running-config segment-routing traffic-eng segment-list vpws1-path
 segment-list vpws1-path
 index 10 address ipv4
 index 20 address ipv4

So if we see currently the route towards NCS5508-3, it’s going via IGP Route and not taking our defined list which is expected.

RP/0/RP0/CPU0:ncs5508-1#show route
Wed Jun 27 14:49:59.487 UTC
Routing entry for
 Known via "ospf 1", distance 110, metric 3, labeled SR, type intra area
 Installed Jun 27 14:47:18.930 for 00:02:40
 Routing Descriptor Blocks, from, via HundredGigE0/1/0/0
 Route metric is 3
 No advertising protos.

So let’s see our L2VPN status.

RP/0/RP0/CPU0:ncs5508-1#show l2vpn xconnect group evpn-vpws detail
Group evpn-vpws, XC vpws1, state is up; Interworking none
 AC: HundredGigE0/2/0/2.1100, state is up
 Type VLAN; Num Ranges: 1
 Rewrite Tags: []
 VLAN ranges: [1100, 1100]
 MTU 9016; XC ID 0x1000001; interworking none
 packets: received 157064234, sent 157063216
 bytes: received 234968088320, sent 234966565392
 drops: illegal VLAN 0, illegal length 0
 EVPN: neighbor, PW ID: evi 1100, ac-id 11003, state is up ( established )
 XC ID 0xc0000001
 Encapsulation MPLS
 Source address
 Encap type Ethernet, control word disabled
 Sequencing not set
 Preferred path Active : SR TE vpws1-policy, Statically configured, fallback enabled
 Tunnel : Up

 EVPN  Local Remote
 ------------ ------------------------------ -----------------------------
 Label 64007 64006
 MTU   9016  9016
 Control word disabled disabled
 AC ID 11001 11003
 EVPN type Ethernet Ethernet

So if we go n shut the primary dynamic path we can see the forwarding table moves over to our segment-list defined for label 16003 which is for NCS5508-3.

RP/0/RP0/CPU0:ncs5508-1#config t
Wed Jun 27 14:58:04.096 UTC
RP/0/RP0/CPU0:ncs5508-1(config)#int HundredGigE0/1/0/0
RP/0/RP0/CPU0:ncs5508-1#show mpls forwarding
Local Outgoing Prefix Outgoing Next Hop Bytes
Label Label or ID Interface Switched
------ ----------- ------------------ ------------ --------------- ------------
16002 16002 SR Pfx (idx 2) Fo0/2/0/18 0
16003 16003 SR Pfx (idx 3) Fo0/2/0/18 0


So thats all, i hope you like the blog and let me know your feedback.