Phase 4: Customer GRE Configuration Example

Cisco IOS Example

# Physical egress interface
interface FastEthernet 0/0
  description to Internet ISP
  ip address 111.111.111.100 255.255.255.252
  ip tcp adjust-mss 1436  [CRITICAL: Must be 1436 or lower]

# GRE tunnel to Cloudflare
interface Tunnel1
  description GRE tunnel to Cloudflare - Primary
  ip address 10.25.2.1 255.255.255.254  [Customer side of /31]
  source 111.111.111.100
  destination 162.159.64.235  [Cloudflare Anycast IP 1]
  tunnel path-mtu-discovery
  no keepalive

interface Tunnel2
  description GRE tunnel to Cloudflare - Secondary
  ip address 10.25.2.3 255.255.255.254
  source 111.111.111.100
  destination 172.64.240.235  [Cloudflare Anycast IP 2]