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New Member

How to find out BGP default route?

I need to redistribute BGP default routes (with ISP and ExtraNet) into OSPF. How can I find out if there's default route existing in BGP routing table?

7 REPLIES
Bronze

Re: How to find out BGP default route?

sh ip bgp 0.0.0.0 tells you if you got a default route in the bgp table.

hope that helps

Roger

New Member

Re: How to find out BGP default route?

Thanks Roger. My Internet router is peering with the ISP router via EBGP. There is supposed to be a default router from my organization to the Internet. If I don't have a existing default route in my Internet router, should I use "ip route 0.0.0.0 0.0.0.0" to create one to the ISP router or can just assume ISP router already has a default route for me and I can learn it from EBGP?

What about the firewall in between?

Bronze

Re: How to find out BGP default route?

Hi,

i do not know how your isp is implementing this...if he is providing a default route to your organisation. but if you do not get a default route via the ebgp i would, as you said, implement a static default route. I would prefer to implement it my self as you are not depending on information you got from the isp.

The question about the firewall is not easy to answer as i do not exactly know the setup you got. but basically it depends on the security policies you got. also a question is what adresses do you use (private or public) and that leads you to if you have to make a network adress translation.

so some more points to consider depending on achieve

Hope that gives you an idea.

Regards

Roger

Re: How to find out BGP default route?

sh ip bgp 0.0.0.0 is the best way to do this.

Otherwise sh ip route 0.0.0.0 you can see the route's admin distance (20 for ebgp and 200 for ibgp)and figure out if the route exists.

New Member

Re: How to find out BGP default route?

Thanks all. If no default route existing, should I generate one pointing to my ISP or ask ISP to generate one on their router, and let my router learn it via BGP?

Re: How to find out BGP default route?

Dear gwhuang,

First the peering with the ISP's depending on what you asking for i mean you may aggred with your ISP to advertise the full routing tabel for you (if your router can save all this routes) or if you aggred that thy will generate only a default route

ANYWAY

If you are running a BGP or any routing protocol with your ISP and you want to know if there is default route coming from your provider or not you could use show ip route x.x.x.x and the output will shown the next-hop address which you learned the route from and the AD wich show the routing protocol that learned the route for BGP there is alot of Useful commands

show ip bgp neighbors 1.1.1.1 received-routes | inc 0.0.0.0

show ip bg x.x.x.x and if it's found check if it's selected or not

Anyway you can add your default route by your self by use ip route 0.0.0.0 0.0.0.0 Next-hop or INT # or ask your ISP to generate default route through the running protocol

Best Regards,

Mounir Mohamed

New Member

Re: How to find out BGP default route?

Thanks all. This is very helpful for me.

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