BGP - Advertise loopback

FrankGuthrieFrankGuthrie Member Posts: 245
in CCNP
Hi all,

I'm studying BGP and using IP Experts CCNP Route on demand video.

Now the instructor is showing an example of confguring BGP and he's using BGP to advertise the loopback address of the Router.

My question is, why would you choose using BGP to advertise the loopback, and not the IGP running in your AS? So what is the advantage of doing this?
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  • networker050184networker050184 Mod Posts: 11,962 Mod
    You usually wouldn't see this in the real world. People usually put loopbacks in for labs to have extra networks to advertise.
    An expert is a man who has made all the mistakes which can be made.
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  • FrankGuthrieFrankGuthrie Member Posts: 245
    Ah oke, thanks for explaining.

    Further down the video you can see this is not working as he already has advertised the loopback via OSPF, and thus the BGP route is not choosen over the lower AD of OSPF. I guess he was just making a point (BGP failure). :)
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  • xXErebuSxXErebuS Member Posts: 230
    FrankGuthrie wrote: »
    Ah oke, thanks for explaining.

    Further down the video you can see this is not working as he already has advertised the loopback via OSPF, and thus the BGP route is not choosen over the lower AD of OSPF. I guess he was just making a point (BGP failure). :)

    He isn't trying to do BGP load sharing is he?
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  • networker050184networker050184 Mod Posts: 11,962 Mod
    Even if are going to do load sharing you aren't going to want to put the loopback you use in BGP. You don't want to form an adjacency with an address learned via BGP. You can start running into recursion problems at that point.
    An expert is a man who has made all the mistakes which can be made.
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  • xXErebuSxXErebuS Member Posts: 230
    networker050184 wrote: »
    Even if are going to do load sharing you aren't going to want to put the loopback you use in BGP. You don't want to form an adjacency with an address learned via BGP. You can start running into recursion problems at that point.

    I agree, I was trying to figure out the purpose of the example.
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  • BeTheNetworkBeTheNetwork Member Posts: 18 ■□□□□□□□□□
    Sorta off-topic, but may be useful. I had a customer in the past that terminated a BGP peering session with 360 Networks (now Zayo) and their router-id was a loopback interface addressed with an RFC 1918 address. 360 updated their access to Alcatel devices and could not recover the BGP peer. After a quick look at documentation, Alcatel's will not peer with router's with a RFC 1918 router-id.

    Again, this is OT from your original question, but I think it points to the hairy nuances associated with BGP.

    Just a quick question about the IPE course, does it cover Peer-Policy Templates in BGP?

    Thanks,
    Brent
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  • FrankGuthrieFrankGuthrie Member Posts: 245
    @****, Peer-Policy Templates in BGP are not covered.

    I think the CCNP course is now free for everone registering with IP Experts. Registering is free and doesn't mean you have to buy 'products from them. The CCNP Route course can be watched online only.
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