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Beginner

Verifying routing

Hello. I have a switch L3 that connects to two ISPs. The routing protocol used is BGP (one ISP is configured with a neighbor weight of 100 and the other is left by default). There is a route-map applied for the two of the ISP that only allows the default route in. I would like to test if I have internet connectivity using the backup ISP, but I cannot bring down any interface or change the configuration, due the fact that this is a production network. Is there a way I can force my tracert or ping to go through the secondary ISP to test the connectivity through it?

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VIP Mentor

Re: Verifying routing

Hello,

 

the easiest way to test would to just ping e.g. 8.8.8.8 using the IP address or the interface of the backup.

 

ping 8.8.8.8 source

 

Hall of Fame Expert

Re: Verifying routing

Hello ,

you can use PBR = Policy Based Routing

 

access-list 15 permit host x.x.x.x

 

route-map PBR permit 10

match address 15

set ip next-hop <Secondary-ISP-next-hop>

 

on internal interface like SVI interface Vlan 50 you apply

interface Vlan 50

ip policy route-map PBR

 

Note : PBR works only on the incoming direction so it needs to be applied on internal interface.

 

In this way a single specific host can test the backup path in the upstream direction.

 

Warning: I supposed you are not doing NAT on your L3 switch but before.

So the x.x.x.x address should be a public address.

To avoid to impact all traffic use a static NAT entry on device performing NAT

 

 

Hope to help

Giuseppe

 

Beginner

Re: Verifying routing

Thank you.
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