Lets start to learn: October 2014

Sunday, 19 October 2014

SLAAC with Stateless DHCP

As discussed in my previous post, we can use SLAAC to auto assign ip address based on the prefix advertised in the RA. However with SLAAC you only get the IPv6 address and the gateway and still need to depend on DHCP for the DNS server, domain name and the other options. This is called Stateless DHCP as it does not track the client mac and the ip (No dhcp binding table is formed).

Please refer the the previous post on how SLAAC works and how to configure it.

http://lets-start-to-learn.blogspot.in/2014/10/ipv6-slaac-gns3-example.html

In this post we'll build upon the previous post and will add Stateless DHCP to it to provide DNS server ip and the domain name to the host devices.

Since GNS3 VPCS was not giving options related to DNS I have created a loopback adapter on my laptop and will be using it to replicate a host machine shown in the topology as a Cloud.

Please refer to my previous posts on how to create a loopback adapter and how to use it in GNS3 as a host machine.

http://lets-start-to-learn.blogspot.in/2014/10/creating-loopback-adapter-on-windows.html

http://lets-start-to-learn.blogspot.in/2014/10/using-vpcs-in-gns3-to-replicate-host.html

Following is the Topology I am using:

I have created an IPv6 DHCP pool on the R1 to provide only DNS Server ip and Domain name:

R1#show running-config | sec ipv6 dhcp

ipv6 dhcp pool Stateless_DHCP
dns-server 2000:1000::1
domain-name Test.com
ipv6 dhcp server Stateless_DHCP

I am using the above dhcp pool just for vlan 10 and following configuration would be required on the vlan 10 SVI :

interface Vlan10

no ip address

ipv6 address 2000:1000::1/64

ipv6 enable

ipv6 nd other-config-flag

ipv6 dhcp server Stateless_DHCP

On the R2 the interface fa0/4 is mapped to vlan 10.

R2#show runn int fa 0/4

Building configuration...

Current configuration : 60 bytes

interface FastEthernet0/4

switchport access vlan 10

end

I had to play with Spanning tree (The Fa 0/4 port was getting into blocked state) before the loopback adapter on my lab could get the ipv6 address and the dhcp configuration.

Ethernet adapter Local Area Connection 3:

Connection-specific DNS Suffix . : Test.com

Description . . . . . . . . . . . : Microsoft Loopback Adapter

Physical Address. . . . . . . . . : 02-00-4C-4F-4F-50

DHCP Enabled. . . . . . . . . . . : No

Autoconfiguration Enabled . . . . : Yes

IPv6 Address. . . . . . . . . . . : 2000:1000::651c:9aca:97a6:3a7e(Preferred)

Temporary IPv6 Address. . . . . . : 2000:1000::8c84:1cb9:4268:7fd0(Preferred)

Link-local IPv6 Address . . . . . : fe80::651c:9aca:97a6:3a7e%17(Preferred)

IPv4 Address. . . . . . . . . . . : 192.168.10.11(Preferred)

Subnet Mask . . . . . . . . . . . : 255.255.255.0

Default Gateway . . . . . . . . . : fe80::ce00:29ff:feb8:0%17

DHCPv6 IAID . . . . . . . . . . . : 503447628

DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-17-EE-19-AD-00-21-CC-C6-CF-CF

DNS Servers . . . . . . . . . . . : 2000:1000::1

NetBIOS over Tcpip. . . . . . . . : Enabled

Connection-specific DNS Suffix Search List :

Test.com

You will also notice that once you configured the IPv6 dhcp scope on the R1 it also joined to some additional group addresses related to dhcpv6

R1#show ipv6 interface

Vlan10 is up, line protocol is up

IPv6 is enabled, link-local address is FE80::CE00:29FF:FEB8:0

Global unicast address(es):

2000:1000::1, subnet is 2000:1000::/64

Joined group address(es):

FF02::1

FF02::2

FF02::1:2

FF02::1:FF00:1

FF02::1:FFB8:0

FF05::1:3

ff02::1:2 All DHCP servers and relay agents on the local network segment (defined in RFC 3315)

ff05::1:3 All DHCP servers on the local network site (defined in RFC 3315)

With DHCPv6 there are very interesting, new terms used and implemented in the way how the DHCPv6 will assign ip addresses to the client devices.The DHCPv6 uses UDP port number 546 for clients and port number 547 for servers.
In IPv6 you had the concept of client identified which was the physical mac address of the client device requesting for the DHCP, with IPv6 we have something called a host identifier, named DUID – Device UID – and a set of interface identifiers. The RFC defines a DUID this way:
A DHCP Unique IDentifier for a DHCP participant; each DHCP client and server has exactly one DUID.
Also each interface has an ID, called IAID – Interface Association Identifier – that is a binding between the interface and one or several IP addresses. Each allocation in the DHCPv6 server is identified by a DUID and a IAID.
If you notices the IPv6 details from the host machine in the above topology it also has a DUID and IAID:

DHCPv6 IAID . . . . . . . . . . . : 503447628

DHCPv6 Client DUID. . . . . . . . : 00-01-00-01-17-EE-19-AD-00-21-CC-C6-CF-CF

You can check the DUID on the Router using the command: show ipv6 dhcp.

R1#show ipv6 dhcp
This device's DHCPv6 unique identifier(DUID): 00030001CC0029B8F000

At the moment there are three types of DUID defined:
1) Link-layer address plus time (DUID-LLT)
2) Vendor-assigned unique ID based on Enterprise Number
3) Link-layer address (DUID-LL)

Cisco uses a structure based on DUID-LLT (link-layer address plus time). The device uses the MAC address from the lowest numbered interface to form the DUID.

The type of DUID-LLT consists of:

• Two octet type field containing the value 1

• Two octet hardware type code. The hardware type MUST be a valid hardware type assigned by the IANA as described in RFC 826. Ethernet uses hardware type 1 and 48-bit MAC address of the device as the link-layer address.

• Four octets containing a time value

• Link-layer address of any one network interface that is connected to the DHCP device at the time that the DUID is generated. The time value is the time that the DUID is generated, represented in seconds since midnight (UTC), January 1, 2000, modulo 2^32.

Lets follow the wireshark capture collected on the PC.

1. The R1 sends out a RA in the Packet 313.

2. The host sends out a Multicast Listener Report to the IP destination address of FF02::16, to which all MLDv2-capable multicast routers listen.

Refer to the RFC: http://tools.ietf.org/html/rfc3810

Here once the host machine has got an RA it has assigned itself and ip address as : 2000:1000::8c84:1cb9:4268:7fd0, and as we know once the device gets a link local address or the Global IPv6 address it also makes itself as the member of the related solicited node multicast group (for both it's link-local and global address). Here the host machine is sending out the multicast listerner report indicating its interest for the solicited node multicast address associated with its Global ipv6 address.

The solicited node multicast address is generated by adding last 24 bits of the link-local/ Global ipv6 address to the prefix : ff02::1:ff00:0/104.

Solicited-Node multicast addresses are used in Neighbor Discovery Protocol for obtaining the layer 2 link-layer addresses of other nodes. For our host the solicited node multicast address becomes:

ff02::1:ff00:0/104 + 68:7fd0 = ff02::1:ff68:7fd0

Please refer to the Wiki page:

http://en.wikipedia.org/wiki/Solicited-node_multicast_address

3. The host machine sends out a network solicitation to the Router at its solicited node multicast address. Nodes send neighbor solicitations to request the link-layer address of a target node while also providing their own link-layer address to the target.

4. The Router sends neighbor advertisements in response to neighbor solicitations and sends unsolicited neighbor advertisements in order to propagate new information quickly.

5. The host sends out a dhcp information request to All dhcp server address ff02::1:2.

6. The server sends out a reply to the host device link local address:

Hope this was helpful :)

Labels: Networking

Saturday, 18 October 2014

IPv6 SLAAC GNS3 Example

Like IPv4, there are a number of different ways that a host can be addressed in IPv6; the two most common in IPv4 are static addressing and via DHCP. DHCP is often preffered as it not only provides a method of dynamically assigning addresses, it also provides a way to assign the host devices other
service information like DNS servers, domain names, and a number of different custom information (DHCP options).

While IPv6 static addressing works exactly the same as IPv4 static addressing, the other methods are quite different than IPv4.

To perform address configuration on IPv6 there are a couple of methods generally divided into two categories : Stateless and Stateful.

Stateful Address Assignment means the DHCP server would be responsible for assigning ip address to the client devices and would also keep a track/record of the client and the ip addresses assigned to them. (This is also called Stateful DHCP address assignment).

With Stateless Address Assignment, the client would generate its own IPv6 address based on the address prefix advertised on the vlan (Interface). Here no DHCP server is involved and the client ip address is not tracked. SLAAC (Stateless Address Auto-config) is this method in which the client devices will generate an address for themselves based on the network prefix advertised in the Router Advertisement (RA) on the local network, by default SLAAC does not provide anything to the client except the IPv6 address and the default gateway, though you can still use DHCP with SLAAC i.e Stateless DHCP to provide the client with other dhcp options like domain name and stuff, however since this being Stateless the dhcp server does not track/record any client device and the ip address assignment.

SLAAC is implemented on the IPv6 client by listening for these local RA’s and then taking the prefix that is advertised to form a unique address that can be used on the network.
For this to work, the prefix that is advertised must advertise a prefix length of 64 bits (i.e., /64).

RA messages are sent by default by most IPV6 routers; these messages are sent out periodically by the router and include information including:

One or more IPv6 prefixes (Link-local scope)
Prefix lifetime information
Flag information
Default device information (Default router to use and its lifetime)

With SLAAC it uses the 64 bit prefix information advertised in the RA and will then dynamically form a host identifier that is 64 bits long and will be suffixed to the end of the advertised prefix to form an IPv6 address.

Originally, the host identifier was formed using the EUI-64 rules (the same that are used to form link local addresses) and many devices still use this method. However, some Microsoft operating systems by default do not use this original method. Instead, they take advantage of some additional privacy extensions that were defined in RFC4941.

Lets see how this was done using the EUI-64 process.

As we can see in the above captures the prefix advertised is 2000:2000::/64 in the Router Advertisement. Lets assume a client whose mac address is : 0050:7966:6802.

The first step of EUI-64 conversion is to split the MAC address in half and place FF:FE in the middle which would be like: 0050:79FF:FE66:6802

Then flip the seventh bit for the resultant from the left i.e most significant byte. For us the most significant byte is 00, when converting it into binary we get 00000000, flipping the seventh bit from left we get : 00000010 in hex this becomes 02.

Thus the final host identifier becomes: 0250:79FF:FE66:6802

Now when the prefix is added to the host identified the final IPv6 address of the client becomes: 2000:2000::0250:79FF:FE66:6802/64.

I have setup a Lab using GNS3 and lets see the results that I get.

Following is the configuration done on Router 1 (Here Router 1 is the Gateway for the vlan 10 and vlan 20).

R1#show run
Building configuration...

Current configuration : 1248 bytes
!
version 12.4
service timestamps debug datetime msec
service timestamps log datetime msec
no service password-encryption
!
hostname R1
!
boot-start-marker
boot-end-marker
!
!
no aaa new-model
memory-size iomem 5
!
!
ip cef
no ip domain lookup
ip domain name lab.local
!
!
ipv6 unicast-routing
!
!
!
interface FastEthernet0/0
switchport mode trunk
!
interface FastEthernet0/1
!
interface FastEthernet0/2
!
interface FastEthernet0/3
!
interface FastEthernet0/4
!
interface FastEthernet0/5
!
interface FastEthernet0/6
!
interface FastEthernet0/7
!
interface FastEthernet0/8
!
interface FastEthernet0/9
!
interface FastEthernet0/10
!
interface FastEthernet0/11
!
interface FastEthernet0/12
!
interface FastEthernet0/13
!
interface FastEthernet0/14
!
interface FastEthernet0/15
!
interface Vlan1
no ip address
!
interface Vlan10
no ip address
ipv6 address 2000:1000::1/64
ipv6 enable
!
interface Vlan20
no ip address
ipv6 address 2000:2000::1/64
ipv6 enable
!
!
no ip http server
ip forward-protocol nd
!
!
control-plane
!
!
line con 0
exec-timeout 0 0
privilege level 15
logging synchronous
line aux 0
exec-timeout 0 0
privilege level 15
logging synchronous
line vty 0 4
login
!
!
end

Router 2 which is just acting as a L2 switch for our Scenario:

R2#show run

Building configuration...

Current configuration : 1154 bytes

version 12.4

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption

hostname R2

boot-start-marker

boot-end-marker

no aaa new-model

memory-size iomem 5

ip cef

no ip domain lookup

ip domain name lab.local

interface FastEthernet0/0

switchport mode trunk

interface FastEthernet0/1

switchport access vlan 10

interface FastEthernet0/2

switchport access vlan 10

interface FastEthernet0/3

switchport access vlan 20

interface FastEthernet0/4

interface FastEthernet0/5

interface FastEthernet0/6

interface FastEthernet0/7

interface FastEthernet0/8

interface FastEthernet0/9

interface FastEthernet0/10

interface FastEthernet0/11

interface FastEthernet0/12

interface FastEthernet0/13

interface FastEthernet0/14

interface FastEthernet0/15

interface Vlan1

no ip address

no ip http server

control-plane

line con 0

exec-timeout 0 0

privilege level 15

logging synchronous

line aux 0

exec-timeout 0 0

privilege level 15

logging synchronous

line vty 0 4

end

In this setup PC1 and PC2 are in vlan 10 while PC3 is in vlan 20. I am using GNS3 VPCS to simulate Host devices. Please refer to the previous post on VPCS for more information.

http://lets-start-to-learn.blogspot.in/2014/10/using-vpcs-in-gns3-to-replicate-host.html

Validating the addresses in the host devices we can see that host devices has picked up related IPv6 address using SLAAC.

VPCS[3]> 1
VPCS[1]> show ipv6

NAME : VPCS[1]
LINK-LOCAL SCOPE : fe80::250:79ff:fe66:6800/64
GLOBAL SCOPE : 2000:1000::2050:79ff:fe66:6800/64
ROUTER LINK-LAYER : cc:00:29:b8:00:00
MAC : 00:50:79:66:68:00
LPORT : 20000
RHOST:PORT : 127.0.0.1:30000
MTU: : 1500

VPCS[1]> 2
VPCS[2]> show ipv6

NAME : VPCS[2]
LINK-LOCAL SCOPE : fe80::250:79ff:fe66:6801/64
GLOBAL SCOPE : 2000:1000::2050:79ff:fe66:6801/64
ROUTER LINK-LAYER : cc:00:29:b8:00:00
MAC : 00:50:79:66:68:01
LPORT : 20001
RHOST:PORT : 127.0.0.1:30001
MTU: : 1500

VPCS[2]> 3
VPCS[3]> show ipv6

NAME : VPCS[3]
LINK-LOCAL SCOPE : fe80::250:79ff:fe66:6802/64
GLOBAL SCOPE : 2000:2000::2050:79ff:fe66:6802/64
ROUTER LINK-LAYER : cc:00:29:b8:00:00
MAC : 00:50:79:66:68:02
LPORT : 20002
RHOST:PORT : 127.0.0.1:30002
MTU: : 1500

The usefulness of SLAAC in any given organization greatly depends on the tracking requirements; because SLAAC does not provide direct tracking the way a stateful DHCP server would, there is no quick way to determine which machine traffic is coming from without tracking the MAC addresses of the clients and calculating their created IPv6 address. This is further complicated by operating systems (like Windows 7) that use SLAAC data protection extensions by default, making tracking even harder, if not impossible, without looking at the addresses assigned to each device. SLAAC isn’t without a purpose, however. On many small networks there is no real need for this specific tracking and the use of SLAAC can simplify the addressing of machines and allow them to access public sites (with or without Network Address Translation (NAT)).

Hope this was helpful :)

Labels: Networking

Monday, 13 October 2014

Music

My Guitar

This is an Ashton D20 darling, a beginners guitar.

Type: Dreadnought Acoustic
Back & Sides: Basswood
Neck: Maple

Product Specifications:
====================

Spruce Top
Basswood Back & Sides
Rosewood Fingerboard
Maple Neck
Matte Finish
Die Cast Chrome Machine heads
Black Binding
Natural Rosette

https://www.youtube.com/watch?v=F3-r48hdDVc

https://www.youtube.com/watch?v=hZSkIPj-qRs

Labels: Music

Saturday, 11 October 2014

Cisco Wireless HA N+1 configuration (Lab Testing)

With software release 7.4 and above Cisco has introduced the N+1 HA feature set within the Cisco Unified Wireless Network (CUWN) framework which allows a single WLC to be used as a backup WLC for N primary controllers.

Following is the configuration/documentation guide:

http://www.cisco.com/c/en/us/td/docs/wireless/technology/hi_avail/N1_High_Availability_Deployment_Guide/Introduction.html

The N+1 HA architecture provides redundancy for controllers across geographically separate data centers with low cost of deployment. Lately I had been working in couple of scenarios and had been not been sure if this is supposed to work over L3 network and so did a small Lab to test the same.

My network setup:

WLC1 (vlan 100)------------L3 Switch -----------------WLC2(vlan200)

APs (vlan 300)

Vlan 100: 192.168.100.0/24

Vlan 200: 192.168.200.0/24

Vlan 300: 192.168.30.0/24

WLC1 Primary:

(WLC-Primary) >show interface summary

Number of Interfaces.......................... 6

Interface Name Port Vlan Id IP Address Type Ap Mgr Guest

-------------------------------- ---- -------- --------------- ------- ------ -----

management 1 100 192.168.100.5 Static Yes No

redundancy-management 1 100 192.168.100.10 Static No No

redundancy-port - untagged 169.254.100.10 Static No No

printer-vlan 1 99 10.10.99.100 Dynamic No No

service-port N/A N/A 0.0.0.0 Static No No

(WLC-Primary) >show redundancy summary

Redundancy Mode = SSO DISABLED

Local State = ACTIVE

Peer State = N/A

Unit = Primary

Unit ID = 50:3D:E5:1A:27:20

Redundancy State = N/A

Mobility MAC = 50:3D:E5:1A:27:20

Redundancy Management IP Address................. 192.168.100.10

Peer Redundancy Management IP Address............ 192.168.100.11

Redundancy Port IP Address....................... 169.254.100.10

Peer Redundancy Port IP Address.................. 169.254.100.11

(WLC-Primary) >show advanced backup-controller

AP primary Backup Controller .................... WLC-Secondary 192.168.200.5

AP secondary Backup Controller ..................

WLC2 Secondary:

(WLC-Secondary) >show interface summary

Number of Interfaces.......................... 6

Interface Name Port Vlan Id IP Address Type Ap Mgr Guest

-------------------------------- ---- -------- --------------- ------- ------ -----

management 1 200 192.168.200.5 Static Yes No

redundancy-management 1 200 192.168.200.10 Static No No

redundancy-port - untagged 169.254.200.10 Static No No

printer-vlan 1 99 10.10.99.100 Dynamic No No

service-port N/A N/A 0.0.0.0 Static No No

virtual N/A N/A 1.1.1.1 Static No No

(WLC-Secondary) >show redundancy summary

Redundancy Mode = SSO DISABLED

Local State = ACTIVE

Peer State = N/A

Unit = Secondary - HA SKU

Unit ID = E0:5F:B9:46:99:00

Redundancy State = N/A

Mobility MAC = 50:3D:E5:1A:27:20

Redundancy Management IP Address................. 192.168.200.10

Peer Redundancy Management IP Address............ 192.168.200.11

Redundancy Port IP Address....................... 169.254.200.10

Peer Redundancy Port IP Address.................. 169.254.200.11

(WLC-Secondary) >show advanced backup-controller

AP primary Backup Controller .................... 0.0.0.0

AP secondary Backup Controller ..................

L3 Switch:

AP-SWITCH1#show cdp neighbors

Capability Codes: R - Router, T - Trans Bridge, B - Source Route Bridge

S - Switch, H - Host, I - IGMP, r - Repeater, P - Phone,

D - Remote, C - CVTA, M - Two-port Mac Relay

Device ID Local Intrfce Holdtme Capability Platform Port ID

WLC-Secondary Gig 1/0/1 152 H AIR-CT550 Gig 0/0/1

TEST-AP-2 Gig 1/0/7 142 R T AIR-LAP12 Gig 0.1

TEST-AP-1 Gig 1/0/20 150 R T AIR-CAP26 Gig 0.1

WLC-Primary Gig 1/0/3 140 H AIR-CT550 Gig 0/0/1

AP-SWITCH1#show runn int gig 1/0/1

Building configuration...

Current configuration : 127 bytes

interface GigabitEthernet1/0/1

switchport access vlan 100

switchport trunk encapsulation dot1q

switchport mode trunk

end

AP-SWITCH1#show runn int gig 1/0/3

Building configuration...

Current configuration : 99 bytes

interface GigabitEthernet1/0/3

switchport trunk encapsulation dot1q

switchport mode trunk

end

AP-SWITCH1#show runn int gig 1/0/7

Building configuration...

Current configuration : 90 bytes

interface GigabitEthernet1/0/7

switchport access vlan 300

switchport mode access

end

Testing:

========

APs configured with dhcp option 43 to join the Primary WLC (192.168.100.5).

Once the APs join the Primary WLC , under high availability configured the Primary and the Secondary WLCs.

Make sure you have configured the secondary WLC (HA-SKU) on the other L3 network as Backup Primary Controller:

In our setup both the APs were on the Primary WLC initially:

Once the connectivity to the Primary WLC is lost (We shut down the port to the Primary-WLC on the Switch). We find the APs automatically falling back to the Secondary.

AP-SWITCH1(config)#int gig 1/0/3

AP-SWITCH1(config-if)#shut

AP-SWITCH1(config-if)#

1w1d: %LINK-5-CHANGED: Interface GigabitEthernet1/0/3, changed state to administratively down

1w1d: %LINEPROTO-5-UPDOWN: Line protocol on Interface GigabitEthernet1/0/3, changed state to down

Licensing:

http://www.cisco.com/c/en/us/td/docs/wireless/technology/hi_avail/N1_High_Availability_Deployment_Guide/N1_HA_Overview.html

HA-SKU as Secondary Controller

With Release 7.4, an HA-SKU controller can be used as a secondary controller. In this example, the secondary controller is running a 50 AP permanent license and is configured to be an HA-SKU controller. Therefore it has a maximum AP capacity of 500.

Labels: Wireless

Using VPCS in Gns3 to replicate host devices in the network topology

The latest version on Gns3 comes with the Virtual PC Simulator that can be used to simulate end host in the network topology in Gns3 and to do simple reachability tests like ping and traceroute. Thought there are other alternatives available as well like, Qemu and Virtual box guest however these are cpu intensive. VPCS is integrated with windows and linux machine and are very light on CPU

The latest version of the GNS3 can be downloaded from here:

http://www.gns3.net/download/

In this post we'll see how we can configured and use VPCS in our small network topology we'll be using. We'll be using as simple L2 (Ethernet Switch) and connecting two PCs in the same vlan and we'll do a simple ping test from one PC to the other.

Lets start building up the topology:

If you don't like Cloud representing the PC you can change the symbol by right clicking on the Cloud.

Let me change the symbols in my topology.

Lets see what configuration is needed to use VPCS. Right click the PC-1 and click on configured. In the node configurator click on the C node and goto NOI UDP.

Use local port as 30000 and remote port as 20000 > click on Add and Apply. Similarly configure the other PC-2 accordingly with local port as 30001 and remote port as 20001.

Once both the PCs are configured, connect them to the Switch using the NOI UDP ports.

In this situation, both the switchport 1 and 2 are configured in the Vlan 1. Lets start the VPCS configure and assign ip address to the two PCs accordingly.

I would be assigning both the devices ip address in the same subnet (192.168.10.0/24).

Lets start up the VPCS. Goto Tools on the Gns3 window and click on VPCS.

This should automatically bring up the windows command prompt, with the VPCS prompt.

Following are the options available:

The VPCS prompt is the terminal for the PCs. You can type 1 to get to the VPCS 1 or 2 to get to the VPCS 2.

Lets assign ip address to both the virtual PCs. Following is the ip address assignment format for the VPCS:

VPCS[1]> ip ?

ip [arguments]
Configure the current VPC's IP settings
arguments:
<address> [/<mask>] [<gateway>]
<address> [<gateway>] [/<mask>]
Set the VPC's ip, default gateway ip and network mask
Default IPv4 mask is /24, IPv6 is /64. In the ether mode,
the ip of the tapx is the maximum host ID of the subnet.
ip 10.1.1.70 /26 10.1.1.65 set the VPC's ip to 10.1.1.70,
the gateway to 10.1.1.65, the netmask to 255.255.255.192,
the tapx ip to 10.1.1.126 in the ether mode.
</mask> may be written as /26, 26 or 255.255.255.192
auto Attempt to obtain IPv6 address, mask and gateway using SLAAC
dhcp -[d|r|x] Attempt to obtain IPv4 address, mask, gateway, DNS via DHCP
-d Show DHCP packet decode
-r Renew DHCP lease
-x Release DHCP lease
dns <ip> Set DNS server <ip>, delete if <ip> is '0'
domain <name> set local domain name
mtu <value> Set IPv4 MTU to <value>, at least 576.

Assigning ip address to the second PC.

Now lets test a Ping from one PC to the other.

As you can see we can use this tool for simple reachability/connectivity test.

Using windows loopback adapter for the connectivity test:
=============================================

We can also use the windows loopback adapter for the similar purpose. Please find my other post on how to create a loopback adapter on windows machine:

http://lets-start-to-learn.blogspot.in/2014/10/creating-loopback-adapter-on-windows.html

You can create multiple loopback adapters on the windows machine and use it likewise. In the below snapshot you would see that I have created two loopback adapters Local Area Connection 3 and 5.

You can use the NOI Ethernet Tab on the Cloud to map the loopback adapter to the PCs. In our setup I have used the loopback adapter 3 and loopback adapter 5 to the two PCs accordingly.