[c-nsp] Full Routes / iBGP Issue & Question

[Scott Granados]

Make sure that each router know’s about the other routers interfaces and can reach the next hop.  I’m betting that router A can’t reach a given network via router B because A can’t get to B’s next hop.  You have to make sure that /30 is distributed in to each somehow either via IGP or BGP depending on your design.  If the next hop isn’t reachable from the opposite router you might see this.  Not sure why some networks appear and some don’t but this is the first really obvious thing I’d check.

On Sep 25, 2014, at 9:40 AM, David Deutsch <david.deutsch at telna.com> wrote:

> Hello all,
> 
> Please excuse my disorganized posting/question, as this is my first 
> posting to the mailing list.
> 
> Currently I am attempting to implement two ASR1002-X routers on my 
> network edge, each with diverse eBGP provider connections receiving full 
> routes. Everything up to a point has gone very well, including reception 
> of full routes, blocking of default routes, local prefs, etc. However I 
> am getting some odd results when iBGP connecting the two together.
> 
> I appears that certain routes from each other are being filtered out, so 
> each router is in some cases aware of both routes to a prefix and in 
> some cases aware of only one. Examples:
> 
> edge01.las.telna.com#show ip bgp
> ...
> *>  1.2.128.0/19     216.115.65.69                  80      0 23005 701 
> 38040 9737 i
>  * i                  10.110.5.21              0     80      0 22911 
> 22822 38040 9737 i
>  * i 1.2.128.0/18     10.110.5.21              0     80      0 22911 
> 22822 38040 9737 i
>  *>                   216.115.65.69                  80      0 23005 
> 701 38040 9737 i
>  * i 1.2.128.0/17     10.110.5.21              0     80      0 22911 
> 22822 38040 9737 i
>  *>                   216.115.65.69                  80      0 23005 
> 19151 38040 9737 i
>  *>i 1.2.160.0/19     10.110.5.21              0     80      0 22911 
> 22822 38040 9737 i
>  *                    216.115.65.69                  80      0 23005 
> 19151 10026 38040 9737 i
>  *>i 1.2.179.0/24     10.110.5.21              0     80      0 22911 
> 22822 38040 9737 9737 23969 i
>  *>i 1.2.180.0/24     10.110.5.21              0     80      0 22911 
> 22822 38040 9737 9737 23969 i
>  *>i 1.2.183.0/24     10.110.5.21              0     80      0 22911 
> 22822 38040 9737 9737 23969 i
>  *>i 1.2.192.0/19     10.110.5.21              0     80      0 22911 
> 22822 38040 9737 i
>  *>i 1.2.192.0/18     10.110.5.21              0     80      0 22911 
> 22822 38040 9737 i
>  *>i 1.2.224.0/19     10.110.5.21              0     80      0 22911 
> 22822 38040 9737 i
>  * i 1.3.0.0/24       10.110.5.21              0     80      0 22911 
> 174 10026 18046 i
> 
> edge02.las.telna.com#show ip bgp
> *>  1.0.128.0/19     199.189.118.149                80      0 22911 
> 22822 38040 9737 i
>  * i 1.0.128.0/18     10.110.5.11              0     80      0 23005 
> 3356 38040 9737 i
>  *>                   199.189.118.149                80      0 22911 
> 22822 38040 9737 i
>  * i 1.0.128.0/17     10.110.5.11              0     80      0 23005 
> 19151 38040 9737 9737 i
>  *>                   199.189.118.149                80      0 22911 
> 22822 38040 9737 9737 i
>  * i 1.0.129.0/24     10.110.5.11              0     80      0 23005 
> 19151 38040 9737 9737 9737 23969 i
>  *>                   199.189.118.149                80      0 22911 
> 174 38040 9737 9737 9737 23969 i
>  *>  1.0.160.0/19     199.189.118.149                80      0 22911 
> 22822 38040 9737 i
> 
> What I don't completely understand is why, when the two ASRs are in a 
> iBGP relationship, some routes are showing on one unit and not the 
> other. Additionally, routes like 1.2.128.0/19 will show both paths on 
> one and not on the other.
> 
> edge01 show ip bgp neigh: http://pastebin.com/uv37gsmm
> edge02 show ip bgp neigh: http://pastebin.com/Q9SiK1ZZ
> 
> edge01 bgp config: http://pastebin.com/rLRDTbDj
> edge02 bgp config: http://pastebin.com/apsPLt3D
> 
> Any help would be highly appreciated!
> 
> --David Deutsch
> 
> 
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