CCNA 4.5: Describe WAN access connectivity options


WAN access connectivity options include MPLS, Metro Ethernet, Broadband PPPoE, Internet VPN (DMVPN, site-to-site VPN, client VPN)


4.5.a MPLS

Multiprotocol Label Switching directs data from one network node to the next based on short path labels rather than long network addresses avoiding complex lookups in a routing table.

  • Multiprotocol - protocol independent transport. Can encapsulate packets of various network protocols
  • Label - data packets are assigned labels
  • Switching - referencing the lookup table, attaching the correct labels and forwarding on
  • Primary purpose is to eliminate the dependence on any one particular layer 2 technology (ATM, FR, SONET, Ethernet)
  • MPLS can ride over any layer-2 network to satisfy different types of traffic
  • MPLS is a packet-switching technology not a circuit-switching technology
  • MPLS can carry any payload including IPv4, IPv6, Ethernet, ATM, DSL, FR
  • MPLS uses labels inside the service provider’s network to identify the best paths inside that network versus the best path as determined by routed endpoints
  • The label value in the MPLS header is changed at each hop through the network
  • MPLS label edge routers will route IPv4 and IPv6 packets coming into and exiting the MPLS network.  They will assign labels to the packets headed to the label switch routers.
  • MPLS label switch routers will route based upon the labels assigned.  They will determine the next hop on the label-switched path and based on that decision they will attach the correct label from a lookup table. Everything else is switched.
  • MPLS is primarily an Internet Service Provider WAN technology


4.5.b Metro Ethernet

MetroE for short, is based on Ethernet standards and used to connect subscribers to larger service networks or the internet

  • Ethernet interfaces tend to be much cheaper than SONET, SDH or PDH
  • Ethernet is typically used in customer networks as well making it easier to connect
  • Ethernet its becoming more popular in residential networks now too (versus coaxial cable)
  • MetroE is an inexpensive way to connect many different sites in a geographical area to each other and to the Internet at Ethernet speeds


4.5.c Broadband PPPoE

Broadband typically means high speed connection that is always on.  Compare it to dial-up that is low speed (56Kbps) and only on when you tell it to connect.

  • High speed in the sense that bandwidth is represented in Mbps vs Kbps
  • As mentioned previously, PPP was invented to introduce authentication, encryption and compression over serial links.  Then PPPoE was introduced as an improvement over PPP since it could be used over Ethernet links of the dial-up type.  Now there is Broadband PPPoE, which institutes PPPoE on Broadband links.


4.5.d Internet VPN

A virtual private network (VPN) is a newtork connection that establishes a secure tunnel between remote peers using a public source, such as the Internet.  VPNs use tunnels to encapsulate data packets within normal IP packets for forwarding over IP-based networks. They use encryption to ensure privacy and authentication to ensure the integrity of data.

  • DMVPN - Dynamic Multipoint VPN
    • Allows branch offices to communicate directly with each other over the Internet
    • The dynamic part means it doesn’t require a permanent VPN connection
    • Uses IPsec Virtual Private networks (VPNs)
  • Site-to-site VPN
    • A VPN connection between two peers, which are typically site routers
    • The VPN tunnel is typically established between site routers and allows all users within that site to use the VPN.
  • Client VPN
    • A VPN connection between a client machine and a site router
    • The VPN tunnel is typically established between a PC running software and a router or VPN concentrator at the site that you want to connect to.
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