Engineering the Vodafone-Idea Merger: A Deep Dive into ISP Integration and Global Reachability

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Preface:

When two big ISPs merge like Vodafone and Idea in India, ensuring global Internet reachability is a technical must. Both operators have separate Autonomous Systems (ASNs), IP address blocks, backbones, peering and transit agreements. Before the merge, engineers need to plan the consolidation of ASNs, harmonize BGP routing policies and integrate IP address resources to avoid route leaks and blackholes. All upstream and peering relationships need to be reviewed and updated to ensure customer prefixes from both legacy networks are globally reachable. In the Vodafone Idea merger scenario this means merging their routing domains, advertising prefixes consistently across international exchanges and validating end to end connectivity to ensure seamless Internet services to millions of customers during and after the merge.


Prerequisite taken before ISP merger:

Kindly follow below steps as a prerequisite before ISP merger --

AS strategy

  • Do:
    • Keep both ASNs for now and interconnect via EBGP (transitional phase).
    • Migrate to a single ASN (final phase).
  • Plan for AS migration, including WHOIS updates and upstream providers.

  IP address space consolidation

  • Harmonize public IP prefixes, no overlaps.
  • Merge or re-aggregate IP pools (e.g., broadband, enterprise, LTE/5G).
  • Update IRR objects.

 BGP policies & route control

  • Merge route maps, prefix lists, community tagging policies.
  • Update inbound and outbound traffic engineering policies (e.g., prepending, MEDs, local pref).
  • Check for route leaks.

 Peering and upstream agreements

  • Merge or renegotiate peering agreements at IXPs.
  • Consolidate upstream transit providers.
  • Make sure prefixes are accepted by all peers and transit providers.

 IBGP & route reflector design

  • Integrate internal BGP topology (route reflectors, confederations if any).
  • Scalability: more route reflectors might be needed.

 Network topology and backbone integration

  • Physically interconnect networks at backbone/core level.
  • Harmonize transport/MPLS backbone — check for differences in technologies (e.g., SR-MPLS vs. LDP, legacy vs. newer gear).
  • Re-plan core and distribution layers to avoid loops or asymmetric routing.

 IGP integration (OSPF/IS-IS)

  • Merge IGP domains carefully.
  • Recalculate areas/levels to avoid flooding and sub-optimal routing.
  • Update route redistribution policies between IGP and BGP.

 MPLS VPN services

  • Merge VRFs and VPN route targets (RTs), no conflicts.
  • Harmonize label allocation policies (label blocks, global or per-platform labels).
  • Update PE-CE configurations without downtime.                                                    DNS & service addressing
  • Update authoritative DNS zones if new prefixes.
  • Update reverse DNS (PTR) record. 

  •    Security & filtering/ Review ingress/egress ACLs and filters.
  • Make sure anti-spoofing filters (e.g., uRPF) are in place.
  • Check firewall policies and border security

  • Customer edge (CE) connectivity
  • Make sure all customer prefixes are reachable from the new merged backbone.
  • Update customer BGP sessions (if customer is multihomed).
  • Plan for no downtime (use temporary tunnels if needed).

 Monitoring & NMS integration

  • Merge monitoring systems (NMS, telemetry, SNMP, flow collectors).
  • Harmonize alerting thresholds and policies.
  • Update inventory and config management databases.

 Service-level agreements (SLA) compliance

  • Plan to meet latency, jitter, availability requirements after merge.
  • Update SLA monitoring and reporting tools.

IPv6 strategy

  • Merge IPv6 prefixes and routing plans.
  • Make sure advertisement and neighbor discovery is correct.

Testing and validation

  • Run full route convergence and failover tests.
  • Check prefix advertisement (use show bgp, route servers, RIPE RIS, etc.).
  • Validate reachability from external monitoring points (e.g., Looking Glass, RIPE Atlas).

Command Line: -

 Please find configuration command line here with:

===================================================================

At Vodafone ISP end ---

Vodafone ISP #

router bgp 65001

 bgp log-neighbor-changes

EBGP with Idea

 neighbor 192.0.2.2 remote-as 65002 

 neighbor 192.0.2.2 description "EBGP peering with Idea"

IBGP with internal RR

 neighbor 10.0.0.2 remote-as 65001

 neighbor 10.0.0.2 update-source Loopback0

  Networks advertised

 network 203.0.113.0 mask 255.255.255.0

 network 198.51.100.0 mask 255.255.255.0

 Prefix list to control advertisement

 ip prefix-list VODA-OUT seq 5 permit 203.0.113.0/24

 ip prefix-list VODA-OUT seq 10 permit 198.51.100.0/24

 route-map VODA-EXPORT permit 10

  match ip address prefix-list VODA-OUT

 neighbor 192.0.2.2 route-map VODA-EXPORT out

==========================================================================

At IDEA ISP end ---

IDEA#

router bgp 65002

 bgp log-neighbor-changes

EBGP with Vodafone

 neighbor 192.0.2.1 remote-as 65001 

neighbor 192.0.2.1 description "EBGP peering with Vodafone"

IBGP within Idea

 neighbor 10.1.1.2 remote-as 65002

 neighbor 10.1.1.2 update-source Loopback0

Networks advertised

 network 203.0.114.0 mask 255.255.255.0

 network 203.0.115.0 mask 255.255.255.0

 Prefix list to control advertisement

 ip prefix-list IDEA-OUT seq 5 permit 203.0.114.0/24

 ip prefix-list IDEA-OUT seq 10 permit 203.0.115.0/24

 route-map IDEA-EXPORT permit 10

  match ip address prefix-list IDEA-OUT

 neighbor 192.0.2.1 route-map IDEA-EXPORT out

==========================================================

During integrated AS

Merger_ISP#

router bgp 65001

 bgp log-neighbor-changes

IBGP within unified AS

 bgp router-id 10.255.255.1

 bgp cluster-id 65001

neighbor 10.0.0.2 remote-as 65001

 neighbor 10.0.0.2 update-source Loopback0

 neighbor 10.1.1.2 remote-as 65001

 neighbor 10.1.1.2 update-source Loopback0

Upstream providers

 neighbor 198.51.100.2 remote-as 65400

 neighbor 203.0.113.2 remote-as 65500

 Networks advertised

 network 203.0.113.0 mask 255.255.255.0

 network 198.51.100.0 mask 255.255.255.0

 network 203.0.114.0 mask 255.255.255.0

 network 203.0.115.0 mask 255.255.255.0

Unified export policy

 ip prefix-list MERGED-OUT seq 5 permit 203.0.113.0/24

 ip prefix-list MERGED-OUT seq 10 permit 198.51.100.0/24

 ip prefix-list MERGED-OUT seq 15 permit 203.0.114.0/24

 ip prefix-list MERGED-OUT seq 20 permit 203.0.115.0/24

 route-map MERGED-EXPORT permit 10

match ip address prefix-list MERGED-OUT

neighbor 198.51.100.2 route-map MERGED-EXPORT out

 neighbor 203.0.113.2 route-map MERGED-EXPORT out

Ingress filter for validation

ip prefix-list CUSTOMER-IN seq 5 permit 203.0.113.0/24

ip prefix-list CUSTOMER-IN seq 10 permit 198.51.100.0/24

!

route-map CUSTOMER-VALIDATION permit 10

 match ip address prefix-list CUSTOMER-IN

!

neighbor 203.0.113.2 route-map CUSTOMER-VALIDATION in

neighbor 198.51.100.2 route-map CUSTOMER-VALIDATION in

 

Soft reset and route refresh support

neighbor 203.0.113.2 soft-reconfiguration inbound

neighbor 198.51.100.2 soft-reconfiguration inbound

 =================================================================

Verification commands

show ip bgp summary

show ip bgp neighbors 203.0.113.2 advertised-routes

show ip bgp neighbors 203.0.113.2 received-routes

show ip bgp neighbors 198.51.100.2 advertised-routes

show ip bgp neighbors 198.51.100.2 received-routes

show ip bgp

show ip route

=======================================================================

Conclusion:

Merging two ISPs, like Vodafone and Idea, is not just a business or branding exercise – it’s a complex network engineering transformation that requires careful planning, robust validation and smooth execution. To get global internet reachability post-merger, you need a harmonized Autonomous System (AS) strategy, merged IP prefix advertisements and consistent routing policies to ensure data flow across both legacy and unified infrastructure. The transition from EBGP interconnects between the two ASNs to a unified IBGP core needs to be accompanied by synchronized integration of MPLS backbones, IGP domains, VRF instances and firewall/security configurations. Route redistribution, prefix filtering, peering agreements and upstream transit changes need to be managed to preserve path consistency and avoid blackholing or loops. Real time monitoring, prefix validation and performance benchmarking is critical during each phase to ensure SLA compliance and operational stability. The Vodafone-Idea merger shows how technical excellence in routing architecture, policy control and backbone integration are the foundation to deliver scalable, reliable and secure internet to millions of customers, domestic and global. As network convergence becomes the new normal in telecom, this is a blueprint for engineering teams to merge complex infrastructures into one single, efficient and future ready digital platform.

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