NetSim – Advanced Routing


NetSim is a discrete event simulator covering a broad range of wired, wireless, mobile and sensor networks. It comes with a simple and user friendly GUI which features drag and drop functionality for devices, links, application etc.

The specifications for the Advanced Routing module are –


Virtual LAN (VLAN) Protocol per IEEE 802.1Q

  • VLAN Tagging, VLAN ID and VLAN Name
  • Access and Trunk Ports
  • Inter VLAN routing
  • VLAN Configuration through GUI or Text file

Detailed L3 Switch Model

  • Switching Techniques
  • Spanning tree protocol and multiple spanning tree instances per switch
  • Unicast, Broadcast and Multicast switching
  • Promiscuous mode


Internet Group Management Protocol (IGMP) per RFC 2236

  • IGMP Message - Query, Report
  • Host State Machine and Router State Machine

Internet Control Message Protocol (ICMP) per RFC 792

  • ICMP Control Message
  • ICMP Cont Polling
  • Router Advertisement

IP Multicasting

  • Host extensions for IP multicasting per RFC 1112
  • IP route tables based on multicast application in host
  • IP route tables changed as per matched bit count

Access Control List(ACL):

  • ACL Action – Permit, Deny
  • ACL Direction - Inbound, Outbound, Both
  • Protocol wise permit blocking
  • Interface Id blocking
  • Source and destination IP Address
  • Source and destination port numbers

Protocol Independent Multicast (PIM), Sparse mode per RFC 7761

  • Shortest Path Tree
  • (*, G) State
  • (S, G) State
  • Designated Router Election
  • Hello Timer, Join Expiry Timer

Network Address Translation (NAT) and Public IP

  • Public IP of Host from WAN Router

Routing Protocols:

  • RIP (Routing Interior Protocol )
    • Update Timer
    • Timeout Timer
    • Garbage Collection Timer
  • OSPF(Open Shortest Path First)
    • LSRefresh Time
    • LSA Maxage
    • Increment Age
    • Maxage Removal Time
    • MinLs Interval
    • SPFCalc Delay
    • Flood Timer
    • ISAdertise Self Interface
    • ISSend Delay Update
    • Area ID
    • Hello Interval
    • Router Dead Interval
    • Router Priority
    • Output Cost
    • Include Subnet Route
    • External Routing Capability
    • Rxmt Interval

Queuing discipline in Router

  • First-in-first-out (FIFO) queuing
  • Round Robin
  • Priority queuing (PQ)
  • Weighted-fair queuing (WFQ)

International Standards Used in Advanced Routing:

IETF RFC’s 1771 & 3121, RFC 2236, RFC 1112, RFC 7761, RFCs 792, 777, 760

Virtual LAN (VLAN) Configuration in NetSim:

VLAN is called as virtual local area network, used in Switches and it operates at layer2 and Layer3. A VLAN, is a group of hosts which communicate as if they were attached to the same broadcast domain, regardless of their physical location

For example, all workstations and servers used by a particular workgroup team can be connected to the same VLAN, regardless of their physical connections to the network or the fact that they might be intermingled with other teams. VLANs have the same attributes as physical LANs, but you can group end stations even if they are not physically located on the same LAN segment.

  • VLAN Tagging
  • VLAN ID and VLAN Name
  • Access and Trunk Ports
  • VLAN Configuration through GUI or Text file
  • Inter VLAN routing


International Standards Used in Advanced Routing:

IETF RFC’s 1771 & 3121, RFC 2236, RFC 1112, RFC 7761

Protocol Independent Multicast (PIM) Configuration in NetSim:

PIM is used between routers so that they can track which multicast packets to forward to each other and to their directly connected LANs.

  • Shortest Path Tree
  • Hello Timer, Join Expiry Timer
  • (*, G) State
  • (S, G) State
  • Designated Router Election

PIM Configuration:


ACL (Access control lists) Configuration in NetSim:

Routers provide basic traffic filtering capabilities, such as blocking Internet traffic, with access control lists (ACLs). An ACL is a sequential list of permit or deny statements that apply to addresses or upper-layer protocols.

An access list is a sequential series of commands or filters. These lists tell the router what types of packets to: permit or deny. When using an access-list to filter traffic, a permit statement is used to “allow” traffic, while a deny statement is used to “block” traffic.

  • ACL Action – Permit ,Deny
  • ACL Direction- Inbound, Outbound, Both
  • Protocol wise permit blockingx
  • Interface Id blocking
  • Source and destination IP Address
  • Source and destination port numbers

ACL Configuration:


Network address translation (NAT) Configuration in NetSim:

NAT (Network Address Translation or Network Address Translator) is the virtualization of Internet Protocol (IP) addresses. NAT helps to improve security and decrease the number of IP addresses an organization needs.

A device that is configured with NAT will have at least one interface to the inside network and one to the outside network. In a typical environment, NAT is configured at the exit device between a stub domain (inside network) and the backbone. When a packet leaves the domain, NAT translates the locally significant source address into a globally unique address. When a packet enters the domain, NAT translates the globally unique destination address into a local address. If more than one exit point exists, each NAT must have the same translation table. NAT can be configured to advertise to the outside world only one address for the entire network. This ability provides additional security by effectively hiding the entire internal network behind that one address. If NAT cannot allocate an address because it has run out of addresses, it drops the packet and sends an Internet Control Message Protocol (ICMP) host unreachable packet to the destination.

Configuring Static Routing in NetSim:

Routers forward packets using either route information from route table entries that configured manually or the route information that is calculated using dynamic routing algorithms. Static routes, which define explicit paths between two routers, cannot be automatically updated; you must manually reconfigure static routes when network changes occur. Static routes use less bandwidth than dynamic routes.

Static routes are used in environments where network traffic is predictable and where the network design is simple. You should not use static routes in large, constantly changing networks because static routes cannot react to network changes. Most networks use dynamic routes to communicate between routers but might have one or two static routes configured for special cases.

Static IP Routing Configuration:


Wireshark Interfacing for Router: pcap files can be recorded at each node which can be opened in Wireshark for protocol analysis

Additional Information:

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