Internet – Dual Last mile

Pain Area and aspects for consideration:-

  • What type of Internet connectivity should take?
  • How can customer achieve better uptime?
  • What would be the hand off Interface?
  • Will it be a cost effective solution?
  • Can customer get extra security on Layer3 device?
  • What happen if last mile connectivity goes down?
  • What should be done when single ISP is presence?
  • How many ports required to connecting Internet connections on CPE?

Solution Proposed – Dual Last Mile

Since Internet is one of useful resource for any organization, so customers cannot afford any downtime because of any xyz reasons from ISP. Although Best way is to have 2-3 internet connectivity from different ISP’s and terminate them into Single Firewall/UTM (multi-port) or 2 Firewall/UTM Device (Active-Standby mode) which offer 99.999% Uptime but this is costly affair. So those customers who does not want to spend more on Internet connectivity but still wanted to have better uptime is to take Internet connectivity from single ISP on dual last mile with different ISP POP and terminate on Single CPE(Dual Power).Customers have to make sure that Service provider does not offer same last connectivity at that location unless if any last goes down that site would be isolated because both the last miles are same, so one link should be on Terrestrial last mile and other would be on RF or use other service provider last mile connectivity to ensure better uptime. And there are various last mile through which Service provider can provide Internet as services to their customer like- Copper, RF, Fiber, VSAT, 2G/3G/4G Dongles. The speed of Internet is measured in Kbps, Mbps, Gbps and there are various tools available on net to measure throughput of the connectivity and there are so many Interfaces to terminate internet connectivity but most widely used is Ethernet because of scalability (Fast Ethernet or Gig Ethernet). Router/Layer 3 Device should have features of NAT/PAT along with 3 Ethernet ports (2Routed and 1 Layer2) so that necessary configuration can be done. Through basic configuration of access list, customer can provide extra security in terms of Permit/Deny on top of it. Default-Gateway IP address of all the machines would be the LAN interface of the Router IP address.  Both links should be terminated on Single Router and run Static routing with IP Tracking Command or use BGP as a Routing Protocol which ensure automatic fail-over on secondary link if primary link goes down.

Internet Services - Dual last mile


Technical Arrangement’s:-

  1. Terminate both the last mile circuits on any Layer3 Device (Router or Layer3 Switch).
  2. Internet Leased Line – Service provider offer LAN Public IP’s which need to configured at LAN Device.
  3. NATTING OR PATTING configuration is required to route Internet on Cloud.
  4. Router should have minimum 2 Layer3 port + 1 Layer2 port CE.
  5. Option-1 CE-PE Routing protocol either Static with IP Tracking command feature.
  6. Users Gateway IP address will be Virtual IP of HSRP/VRRP in case 2 CPE’s at customer end, unless Default gateway IP of LAN interface of the Router.
  7. Option-2 configured eBGP with Private AS no along with BGP Attributes (Weight and Local Preference for Outgoing traffic and AS Prepend for influencing incoming traffic).



Akshay Sharma

AKshay has a rich experience of 10+ years in data and telecom domains. He is working as a solution architect in a reputed Telecom in India from the last 5 yrs and has diversified experience in providing robust network solution to SMB and enterprise segment. His core expertise is in DSL broadband/IP/MPLS/Routing and switching with hands on multiple telecom equipment’s and had done multiple certifications into his long career.

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