Question on default IP route to internet gateways

[Jagan1976]

Hi guys,

I found one of my site is configured by my predecessor with 2 default routes.

At this site, they have 2 internet links and one ISR which works as the LAN gateway and firewall.

In this ISR, there are set with two default routes :

IP route 0.0.0.0 0.0.0.0 xx.xx.xx.xx

IP route 0.0.0.0 0.0.0.0 yy.yy.yy.yy

How does the router chooses which path to take in this case?

Is this for redundancy, if one internet link goes down, the other link is utilized?

thanks in advance.

[Peter Paluch · Accepted solution]

Hi,

This configuration provides both load balancing and redundancy. The router will use both links to send data to internet - the mechanism to choose a particular link is a part of the Cisco Express Forwarding (CEF) functionality that handles the routing tasks on Cisco routers. Usually, CEF performs a per-destination load balancing in which all packets from a particular source to a particular destination within the same target network are routed over a particular link, and if the combination [source, destination] changes while the target network is still the same, the router will potentially choose a different link.

So in your case, both those links are utilized, not just one, and if one of them goes down, the remaining one will continue handling all internet-bound traffic.

Best regards,
Peter