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Beginner

Using default routes learned from OSPF via adjacent switches or own switch def routes

Hi ,

 

Both my core switches has default routes going to routers. How can I check if the core switches is using its own default route or def route OSPF learned from adjacent core switches? 

5 REPLIES 5
Beginner

Re: Using default routes learned from OSPF via adjacent switches or own switch def routes

Hi mr,

You should use command below

Show ip route 0.0.0.0/0

If it is static route => route 0.0.0.0/0 is owner of this core switch

if it is route learn via ospf => check next hop and you will know default route learn from (maybe learn from router of other core switch) ?

Thanks and Brgs,

VIP Advisor

Re: Using default routes learned from OSPF via adjacent switches or own switch def routes

Hi there,

If the 'own switch default route' is a statically configured route defined by specifying a next-hop IP (instead of just an exit interface) then providing the next-hop is reachable via an interface which is up/up, then the static route would be visible in the routing table~:

sh ip route static

 

A route learned via OSPF would be displayed with the command:

sh ip route ospf

 

If both routes were valid, then keep in mind that the static route would have a lower Administrative Distance than the OSPF route. Therefore the static route would always take precedence over the OSPF route.

 

cheers,

Seb.

VIP Advisor

Re: Using default routes learned from OSPF via adjacent switches or own switch def routes

Hello


@getaway51 wrote:

Both my core switches has default routes going to routers. How can I check if the core switches is using its own default route or def route OSPF learned from adjacent core switches? 


The core switches will use their own defaults and not the advertised ospf ones due to the lower administrative distance value of the core switches defaults.



kind regards
Paul

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Beginner

Re: Using default routes learned from OSPF via adjacent switches or own switch def routes

Can I see the "lower administrative distance value" when i saw ip route 0.0.0.0/0?

Does this means i will see two def route 0.0.0.0/0, each with different preference?

VIP Advisor

Re: Using default routes learned from OSPF via adjacent switches or own switch def routes

show ip route

 

will give output like:

S*     0.0.0.0/0 [1/0] via 192.168.1.1

The element [1/0]   indicates an AD of 1 and a metric of 0 

 

Only the route with the lowest AD will be installed in the routing table.

 

cheers,

Seb.

 

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