What is VPCS?

VPCS (Virtual PC Simulator) is a light-load PC simulator that allows you to use VPCS on your GNS3 project’s network diagram to verify network connectivity such as pings and traceroute. Using VPCS will reduce the load on your PC.

This section explains how to configure VPCS and the operations such as Ping and Traceroute.

VPCS Configuration

IP address/subnet mask and default gateway configuration (static)

Connect to the VPCS console and configure the IP address/subnet mask and default gateway with the following commands.

VPCS IP address/subnet mask and default gateway configuration

VPCS>ip <ip-address> <subnetmask> <default-gateway>

<ip-address> : IP address
<subnetmask> : Subnetmask
<default-gateway> : Default gateway IP address

Configuring the IP address of the DNS server

The following command is used to configure the IP address of the DNS server.

VPCS Configuring the IP address of the DNS server

VPCS>ip dns <dns-server>

<dns-server> : DNS server IP address

DHCP Client

As a DHCP client, the following commands can be used to obtain IP addresses and other information from the DHCP server.

VPCS DHCP Client configuration

VPCS>ip dhcp

Configuring host name

To change the host name, enter the following command

VPCS Configuring host name

VPCS>set pcname <name>

<name> : Host name

Verify TCP/IP configuration.

To verify the IP address and other TCP/IP configurations, enter the following commands.

VPCS TCP/IP設定の確認

VPCS>show ip

Clear TCP/IP Configuration

To remove the IP address and other TCP/IP configurations, you can use the following command.

VPCS Clear TCP/IP configuration.

VPC>clear ip

Saving Configurations

To save your configuration, use the save command.

VPCS Saving Configurations

VPCS>save <file-name>

<file-name> : 設定ファイル名

If you omit the configuration file name, the configuration is saved in the default starup.vpc file. The path to the configuration file is<GNS project path>\project-files\vpcs\<VPCS UUID>\.

VPCS Operation

Ping

To execute a ping, use the following command.

VPCS Ping

VPCS>ping <ip-address>

<ip-address> : destination IP address

TCP Ping/UDP Ping

In addition to regular pings, TCP and UDP pings can also be executed. You can easily send TCP segments and UDP datagrams from VPCS. You can send TCP segments via TCP ping with the following command.

VPCS TCP Ping

VPCS>ping <ip-address> -P 6 -p <port>

<ip-address> : 宛先IPアドレス
<port> : 宛先ポート番号

The “-P 6” stands for TCP, where 6 is the protocol number for TCP.

To send a UDP datagram with a UDP ping, use the following command.

VPCS UDP Ping

VPCS>ping <ip-address> -P 17 -p <port>

<ip-address> : 宛先IPアドレス
<port> : 宛先ポート番号

The “-P 17” represents UDP, where 17 is the protocol number for UDP.

traceroute

To execute a traceroute, use the following command

VPCS traceroute

VPCS>trace <ip-address>

<ip-address> : 宛先IPアドレス

Display the ARP cache

To verify the ARP cache, you can use the following command.

VPCS Display the ARP cache

VPCS>show arp

VPCS Configuration Example

Consider an example of a VPCS configuration.

RR1 has a DHCP pool configured as a DHCP server. Also, ACLs are applied to Fa0/0.

R1#show running-config | section ip dhcp
no ip dhcp use vrf connected
ip dhcp pool AAA
   network 192.168.12.0 255.255.255.0
   default-router 192.168.12.1
   dns-server 8.8.8.8
R1#show running-config | section access-list
access-list 100 permit tcp any any eq 80 
access-list 100 permit udp any any eq 53
access-list 100 permit ip any any
R1#show run int fa 0/0
Building configuration...

Current configuration : 121 bytes
!
interface FastEthernet0/0
 ip address 192.168.12.1 255.255.255.0
 ip access-group 100 in
 duplex auto
 speed auto
end

TCP/IP configuration (static)

Configure TCP/IP settings to VPCS statically.

  • IP address/subnetmask : 192.168.12.100/24
  • Default gateway : 192.168.12.1
  • DNS server : 8.8.8.8

VPCS

VPCS> ip 192.168.12.100 255.255.255.0 192.168.12.1
Checking for duplicate address...
PC1 : 192.168.12.100 255.255.255.0 gateway 192.168.12.1

VPCS> ip dns 8.8.8.8

VPCS> show ip

NAME        : VPCS[1]
IP/MASK     : 192.168.12.100/24
GATEWAY     : 192.168.12.1
DNS         : 8.8.8.8
MAC         : 00:50:79:66:68:00
LPORT       : 10016
RHOST:PORT  : 127.0.0.1:10017
MTU:        : 1500

TCP/IP Configuration (DHCP)

Remove the VPCS static configuration and make it a DHCP client.

VPCS

VPCS> clear ip
IPv4 address/mask, gateway, DNS, and DHCP cleared

VPCS> ip dhcp
DDORA IP 192.168.12.3/24 GW 192.168.12.1

VPCS> show ip

NAME        : VPCS[1]
IP/MASK     : 192.168.12.3/24
GATEWAY     : 192.168.12.1
DNS         : 8.8.8.8
DHCP SERVER : 192.168.12.1
DHCP LEASE  : 86396, 86400/43200/75600
MAC         : 00:50:79:66:68:00
LPORT       : 10016
RHOST:PORT  : 127.0.0.1:10017
MTU:        : 1500

Ping

Ping from VPCS to R1.

VPCS

VPCS> ping 192.168.12.1
84 bytes from 192.168.12.1 icmp_seq=1 ttl=255 time=6.259 ms
84 bytes from 192.168.12.1 icmp_seq=2 ttl=255 time=6.433 ms
84 bytes from 192.168.12.1 icmp_seq=3 ttl=255 time=7.197 ms
84 bytes from 192.168.12.1 icmp_seq=4 ttl=255 time=5.321 ms
84 bytes from 192.168.12.1 icmp_seq=5 ttl=255 time=6.258 ms

TCP Ping/UDP Ping

Execute a TCP ping on destination port number 80 and a UDP ping on destination port number 53 from VPCS to R1.

VPCS

VPCS> ping 192.168.12.1 -P 6 -p 80
Connect   [email protected] RST returned
Connect   [email protected] RST returned
Connect   [email protected] RST returned
Connect   [email protected] RST returned
Connect   [email protected] RST returned

VPCS> ping 192.168.12.1 -P 17 -p 53
*192.168.12.1 udp_seq=1 ttl=255 time=10.087 ms (ICMP type:3, code:3, Destination port unreachable)
*192.168.12.1 udp_seq=2 ttl=255 time=3.372 ms (ICMP type:3, code:3, Destination port unreachable)
*192.168.12.1 udp_seq=3 ttl=255 time=5.326 ms (ICMP type:3, code:3, Destination port unreachable)
*192.168.12.1 udp_seq=4 ttl=255 time=8.978 ms (ICMP type:3, code:3, Destination port unreachable)
*192.168.12.1 udp_seq=5 ttl=255 time=6.009 ms (ICMP type:3, code:3, Destination port unreachable)

If you look at show access-lists on R1, you can see that it is receiving a TCP segment on destination port number 80 and a UDP segment on destination port number 53.

R1

R1#show access-lists
Extended IP access list 100
    10 permit tcp any any eq www (30 matches)
    20 permit udp any any eq domain (30 matches)
    30 permit ip any any (128 matches)

traceroute

Execute a traceroute from VPCS to R1.

VPCS

VPCS> trace 192.168.12.1
trace to 192.168.12.1, 8 hops max, press Ctrl+C to stop
 1   *192.168.12.1   9.203 ms (ICMP type:3, code:3, Destination port unreachable)

Display the ARP cache

Use the show arp command to display the VPCS ARP cache.

VPCS

VPCS> show arp

cc:01:29:a8:00:00  192.168.12.1 expires in 63 seconds

How to use GNS3