Two sites, two switches, and issue setting up RIP

[Stephen_Stormon]

We have two sites with two Summit switches at each. We had a MPLS connection between the two sites and have since added a direct point to point (P2P) connection between the two locations. What we want to do it to configure the network so that all traffic between these sites will default to using the P2P connection and fail over to the MPLS is necessary. We don't believe our license allows for the use of OSPF, so we decided to attempt to implement RIP. We configured RIP to only export "direct routes". Things seem to be going well, but there is a route in each site that for some reason will not become the default and we don't know why:

Related routes at one end (172.22.16.5 is the MPLS router at the site and 172.19.1.1 is the P2P address at the far end of the P2P)
Ori Destination Gateway Mtr Flags VLAN Duration
#s 172.22.62.0/20 172.22.16.5 2 UG---S-um--f- Internal_Appliances 0d:0h:40m:13s
r 172.22.62.0/20 172.19.1.1 2 UG-D---um---- P2P_Express 0d:1h:56m:37s
#s 201.133.58.0/24 172.22.16.5 1 UG---S-um--f- Internal_Appliances 0d:2h:3m:4s
#r 201.133.58.64/26 172.19.1.1 2 UG-D---um--f- P2P_Express 0d:1h:56m:37s

Related routes at the other end (172.22.62.3 is the MPLS router at the site and 172.19.1.14 is the P2P address at the far end of the P2P):
Ori Destination Gateway Mtr Flags VLAN Duration
#s 144.202.234.0/24 172.22.62.3 1 UG---S-um--f- Default 775d:17h:39m:55s
#r 144.202.234.128/25 172.19.1.14 2 UG-D---um--f- P2P_Express 0d:2h:9m:37s
#s 172.22.16.0/20 172.22.62.3 1 UG---S-um--f- Default 0d:1h:55m:38s
r 172.22.16.0/20 172.19.1.14 2 UG-D---um---- P2P_Express 0d:2h:9m:38s
Why is it that the one route acquired by rip became the "Preferred unicast and multicast route" but the other one did not? Is the issue because there is already a statically defined route for that network and static routes take precedence over RIP imported routes?

[dflouret]

Change the cost of the static routes so it is higher than the cost of the RIP routes.

[Stephen_Stormon]

When I attempt to issue the command "enable rip export direct cost" with either a "0" or "1" as the value for the metric, the rip routes still get exported as having a metric of "2". Is there any way around that, or do I just deal with it and then assign the static routes a value of "3" or higher?

[dflouret]

Stephen,

From EXOS User Guide:

Multiple Routes
When there are multiple, conflicting choices of a route to a particular destination, the router picks the route with the longest matching network mask. If these are still equal, the router picks the route using the following default criteria (in the order specified):
• Directly attached network interfaces
• Static routes
• ICMP redirects
• Dynamic routes
• Directly attached network interfaces that are not active.


In the first case, the static route and the dynamic route to 172.22.62.0/20 have the same cost, so the precedence rule dictates that the static route will be the one chosen as active.

The second RIP route is active even though it has a higher cost, because it is MORE SPECIFIC (/26) than the static route (/24). That means that all traffic to 201.133.58.0/24 will use the static route EXCEPT traffic destined to 201.133.58.64/26, that will use the dynamic route.

In the second case, the cost of the static route to 172.122.16.0 is LOWER than the dynamic route, so it will be preferred.

Again, the second RIP route is active even though it has a higher cost, because it is MORE SPECIFIC (/25) than the static route (/24). That means that all traffic to 144.202.234.0/24 will use the static route EXCEPT traffic destined to 144.202.234.128/25, that will use the dynamic route.

If you want your dynamic routes (RIP) to have precedence, you have to increase the cost of the static routes using the metric keyword.

configure iproute add [ipNetmask | ip_addr mask] gateway {bfd} {metric} {multicast | multicast-only | unicast | unicast-only} {vlan egress_vlan} {vr vrname}