This is a continuation of my VIRL, CML blog series. VIRL/CML overview is covered here. In this blog, I will cover L2 connectivity usecase. L3 support has been present in VIRL for quite some time, L2 support was added recently in VIRL. I used the IOSvL2 experimental image for this usecase. Official L2 image is yet to be released.
Following is the topology I created with IOS L2 nodes and servers attached to the nodes.
Servers1 and 3 are in vlan 10, Server 2 and 4 are in vlan 20. To configure the VLAN, we need to select the link in node view of server and add vlan. I did not add the vlan to the trunk links, Autonetkit automatically adds it. I was not able to specify multiple vlans in the vlan text box, not sure if that’s on purpose. I felt that specifying multiple vlans would be needed for trunking interfaces.
Following is the Autonetkit visualization view in L2 mode.
After running the simulation, lets look at relevant outputs in switch 1. We can see the relevant VLANs configured in the trunking interface and that STP has converged.
iosvl2-1#show vlan VLAN Name Status Ports ---- -------------------------------- --------- ------------------------------- 1 default active Gi0/0 10 VLAN0010 active Gi0/1 20 VLAN0020 active Gi0/2 1002 fddi-default act/unsup 1003 token-ring-default act/unsup 1004 fddinet-default act/unsup 1005 trnet-default act/unsup iosvl2-1#show interfaces trunk Port Mode Encapsulation Status Native vlan Gi0/3 on 802.1q trunking 1 Port Vlans allowed on trunk Gi0/3 1-4094 Port Vlans allowed and active in management domain Gi0/3 1,10,20 Port Vlans in spanning tree forwarding state and not pruned Gi0/3 10,20 iosvl2-1#show spanning-tree summary Switch is in pvst mode Root bridge for: none Extended system ID is enabled Portfast Default is disabled PortFast BPDU Guard Default is disabled Portfast BPDU Filter Default is disabled Loopguard Default is disabled EtherChannel misconfig guard is enabled Configured Pathcost method used is short UplinkFast is disabled BackboneFast is disabled Name Blocking Listening Learning Forwarding STP Active ---------------------- -------- --------- -------- ---------- ---------- VLAN0001 1 0 0 1 2 VLAN0010 0 0 0 2 2 VLAN0020 0 0 0 2 2 ---------------------- -------- --------- -------- ---------- ---------- 3 vlans 1 0 0 5 6
Following are the access vlan ip addresses on the servers.
cisco@server-1:~$ ifconfig eth1
eth1 Link encap:Ethernet HWaddr fa:16:3e:bc:93:d3
inet addr:10.0.0.5 Bcast:10.0.0.7 Mask:255.255.255.252
inet6 addr: fe80::f816:3eff:febc:93d3/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:338 errors:0 dropped:286 overruns:0 frame:0
TX packets:7 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:31874 (31.8 KB) TX bytes:578 (578.0 B)
cisco@server-2:~$ ifconfig eth1
eth1 Link encap:Ethernet HWaddr fa:16:3e:13:66:bc
inet addr:10.0.0.9 Bcast:10.0.0.11 Mask:255.255.255.252
inet6 addr: fe80::f816:3eff:fe13:66bc/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:342 errors:0 dropped:288 overruns:0 frame:0
TX packets:10 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:32102 (32.1 KB) TX bytes:788 (788.0 B)
cisco@server-3:~$ ifconfig eth1
eth1 Link encap:Ethernet HWaddr fa:16:3e:b9:e3:c7
inet addr:10.0.0.6 Bcast:10.0.0.7 Mask:255.255.255.252
inet6 addr: fe80::f816:3eff:feb9:e3c7/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:331 errors:0 dropped:285 overruns:0 frame:0
TX packets:7 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:30718 (30.7 KB) TX bytes:578 (578.0 B)
cisco@server-4:~$ ifconfig eth1
eth1 Link encap:Ethernet HWaddr fa:16:3e:2e:ce:f8
inet addr:10.0.0.10 Bcast:10.0.0.11 Mask:255.255.255.252
inet6 addr: fe80::f816:3eff:fe2e:cef8/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:352 errors:0 dropped:290 overruns:0 frame:0
TX packets:10 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:33496 (33.4 KB) TX bytes:788 (788.0 B)
Server 1 is able to talk to Server 3, Server 1 is not able to talk to Server 2.
cisco@server-1:~$ ping -c1 10.0.0.6 PING 10.0.0.6 (10.0.0.6) 56(84) bytes of data. 64 bytes from 10.0.0.6: icmp_seq=1 ttl=64 time=24.3 ms --- 10.0.0.6 ping statistics --- 1 packets transmitted, 1 received, 0% packet loss, time 0ms rtt min/avg/max/mdev = 24.305/24.305/24.305/0.000 ms cisco@server-1:~$ ping -c1 10.0.0.9 PING 10.0.0.9 (10.0.0.9) 56(84) bytes of data. From 10.255.0.96 icmp_seq=1 Destination Host Unreachable --- 10.0.0.9 ping statistics --- 1 packets transmitted, 0 received, +1 errors, 100% packet loss, time 0ms
There are scenarios where we would need to capture packets to isolate issues. Below is 1 approach to capture packets. In recent VIRL versions, packet capture is integrated with User workspace management. In the version I am using, it was not integrated, so I needed to use this approach below as specified in VIRL guide. First, we need to download virl-utils scripts to our VIRL server.
git clone https://github.com/VIRL-Open/virl-utils
Then we can see the list of interfaces that are active in the simulation. For this example:
virl@virl:~/virl-utils$ ./list.py guest +---------------+----------+-----------+----------------------+----------------+ | Project | Topology | Node | Link | Interface | +---------------+----------+-----------+----------------------+----------------+ | My_Topologies | Iosl2 | iosvl2-1 | iosvl2-1-to-server-1 | tap2e36867e-7d | | | | iosvl2-1 | iosvl2-1-to-server-2 | tapad467a83-6a | | | | iosvl2-1 | Management Network | tapc83c2b15-a0 | | | | iosvl2-1 | iosvl2-1-to-iosvl2-2 | tapcce7993b-9a | | | | iosvl2-2 | Management Network | tap0bcd5eeb-1e | | | | iosvl2-2 | iosvl2-1-to-iosvl2-2 | tap12cce891-f4 | | | | iosvl2-2 | iosvl2-2-to-server-3 | tap770b51ba-14 | | | | iosvl2-2 | iosvl2-2-to-server-4 | tapa1a0b4f5-1b | | | | server-1 | Management Network | tap5c186a88-e7 | | | | server-1 | iosvl2-1-to-server-1 | tap604bb385-e4 | | | | server-2 | iosvl2-1-to-server-2 | tap32f6c323-a2 | | | | server-2 | Management Network | tap42e2e4cc-fc | | | | server-3 | Management Network | tap0542641e-ae | | | | server-3 | iosvl2-2-to-server-3 | tapc64bc257-95 | | | | server-4 | iosvl2-2-to-server-4 | tap7284e62d-b9 | | | | server-4 | Management Network | tap754730e8-82 | | | | ~mgmt-lxc | Management Network | tap3ad61080-80 | | | | ~mgmt-lxc | ~lxc-flat | tap96b397bf-f5 | +---------------+----------+-----------+----------------------+----------------+
Lets do a ping between Server 1 and Server 3 and capture on interface tapcce7993b-9a. We can see the ping request and response as seen below.
virl@virl:~/virl-utils$ sudo tcpdump -vvni tapcce7993b-9a icmp
tcpdump: WARNING: tapcce7993b-9a: no IPv4 address assigned
tcpdump: listening on tapcce7993b-9a, link-type EN10MB (Ethernet), capture size 65535 bytes
11:28:23.992075 IP (tos 0x0, ttl 64, id 7507, offset 0, flags [DF], proto ICMP (1), length 84)
10.0.0.5 > 10.0.0.6: ICMP echo request, id 1412, seq 1, length 64
11:28:23.993807 IP (tos 0x0, ttl 64, id 1311, offset 0, flags [none], proto ICMP (1), length 84)
10.0.0.6 > 10.0.0.5: ICMP echo reply, id 1412, seq 1, length 64
Sreenivas Makam's Blog 
Very good post thanks.