BGP next-hop-self command

[jeffbriones]

Hi guys,

Can someone enlighten me on these command. Im using this command on my ibgp. Will this command make the router the next-hop if that router is connected and configured for ibgp ?

INTERNET--Router(next-hop-self)--IBGP --- Internalrouter --- mynetworks

Thanks.

jeff

[atif.awan]

For EBGP sessions the nexthop is the IP Address of external neighbor (NBMA and multiaccess media are exceptions). Sometimes you want to change it when advertising it to your IBGP peers inside your AS. In order to achieve this the nexthopself command is used for IBGP sessions. All IBGP neighbors will see the external route with a modified nexthop. The consequence is that you do not need to advertise the external link address space into your IGP for reachability purposes.

In your case if you are using the next-hop-self then your exit router connected to the internet will be the nexthop for all routes advertised from this router to IBGP peers (provided the next-hop-self per neighbor or for peer-group is configured)

[jeffbriones]

Hi,

I tried configuring IBGP on my router without putting the next-hop-self command. Checking the routes, all my routes on RouterB router points to my router's peering ip address on the ISP. What do you think is the best option here? Can i use IGP on RouterB and then inject it on my Router A? Can you provide me a sample config, wherein all configured networks on RouterB can go to the internet.

INTERNET -- (peer ip) RouterA -IBGP- RouterB --- lan side

tnx.

jeff

[atif.awan]

When you see all routes on Router B pointing to ISP router as the next-hop then it is normal behavior as I had described in my previous post.

Before recommending anything I need to understand what you are trying to achieve. The use of next-hop-self command on Router_A will modify the next-hop so that Router_B sees all external routes with next hop as Router_A instead of ISP.

From the second part of your post you seem to be asking for a way to advertise your internal networks out to the world. Is that correct? Can you provide more details?

[jeffbriones]

Hi,

Here's what im trying to achieve. I acquired another ip address block which is 200.189.10.0/24. I already advertised this to my provider using this command.

router bgp

network 200.189.10.0

ip rotue 200.189.10.0 255.255.255.0 null 0

I want this new block to be used by my network for internet connectivity.Here's the diagram

INTERNET -BGP- RouterA - RouterB - (E0/0)mynetwork(10.0 network)

Thats why i tried using IBGP between RouterA and RouterB, can i do these by using IGP for RouterB so that all networks that is configured can access the internet?

thanks.

jeff

[vladrac-ccna]

Hello Jeff,

Cant you use default routes to go from your network (10.0.0.0/8) to the INTERNET?

You'd advertise this route from Router B towards your network pointing to router B and Router B would then receive a default route from Router A.

do you really need to receive BGP routes from Internet on router B? or can you use a 0.0.0.0/0 to go out?

Let us know,

vlad

[jeffbriones]

Hi vlad,

i already used default routes. Im trying to use redistribution on my eigrp instead of default route. How can i achieve this ?

tnx

jeff

[atif.awan]

Jeff,

If you have a single connection to your ISP (as per your diagram) then you do not need BGP. It is better if you configure a default on Router_A and redistribute it into your eigrp. The provider can configure a static route for your new block pointing to your outside interface.

[jeffbriones]

Hi,

Ill be using two isp soon,thats why my config is BGP. How can i use redistribution instead of putting a default route on my other network to reach the internet ? Im still finding a similar scenario for my network

tnx

jeff

[atif.awan]

Multihoming to two different ISPs is not a trivial design so you have to think forward and plan well before you implement it.

For your existing case if you are receiving a default route from your ISP via BGP then you can redistribute that into your IGP (EIGRP). It is not recommended to redistribute the complete BGP routing table into an IGP as it can quickly bog down your routers.