May 12


Scope: As part of my project I need to test the best routing option to use such that WAN traffic leaves the network without much disruption. I will be using ASA firewall for inter VLAN routing and this firewall will send traffic to gateway routers for any access to the outside world.
The router with higher capacity link should be preferred rotuer and the second router should work as backup incase the primary one fails. Now, either all three devices can participate in EIGRP process such that routing updates are populated automatically if a link on the primary router fails or interface goes down. Other option we have is to use HSRP between two routers and using HSRP address as default gateway for the firewall. The third option is to use EIGRP between firewall and primary Router and floating static rotuer with higher administrative distance to come into effect if the link to primary router fails.
The following labs are prepared to test the all three option to measure the disruption in Sec when primary router fails and the time it takes to route traffic via alternative link.


  • It takes 9 Sec for HSRP Gateway address to become available after the WAN Link on primary link fails.
  • It take 9 Sec for HSRP Gateway address to become available after the WAN link on primary router becomes online and primary router takes ownership of the HSRP IP address.
  • It 17 Sec before alternative route to WAN router becomes available if WAN link on primary router fails.
  • When the WAN Link on primary router becomes available there is no disruption to traffic and primary link starts being utilized.
EIGRP and Static Routes
  • In this lab EIGRP is used between firewall and primary gateway. 
  • Floating static routes are configured on firewall and primary router with higher administrative distance such that if primary router accessible via EIRP fails then the static routes becomes active and traffic is routable.
  • It takes 17 Sec when primary routes become unavailable and traffic takes the alternative route.
  • There is no disruption to traffic when the primary link becomes available


We can either use EIGRP or HSRP. With EIGRP the disruption is for once but lasts for 17 Sec. However with HSRP disruption is for shorter period of 9 Sec but happens twice.



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