BGP next-hop

Brett Watson brett at the-watsons.org
Thu Sep 30 19:01:11 CDT 2010


On Sep 30, 2010, at 4:57 PM, Randy Bush wrote:

>>> it seems it gets the bgp route for 147.28.0.0/16 and then can not
>>> resolve the next hop.  it would not recurse to the default exit.
>>> 
>>> of course it was solved by
>>>    ip route 147.28.0.0  255.255.0.0  42.666.77.11
>>> but i do not really understand in my heart why i needed to do this.
>> 
>> Neither do I, Randy.
> 
> a good friend at cisco says he will take the time to write up why in the
> next day or two.

Only thing I can guess from the Cisco doc that says:

"To prevent the creation of loops through oscillating routes, the multihop will not be established if the only route to the multihop peer is the default route (0.0.0.0)."

Is that they think they're saving you from shooting yourself in the foot, if you learn the route to 147.28.0.0/16 via BGP (which your multihop peer address falls in), yet you have a default route of 0.0.0.0? But then you'd simply recursively look up the FIB route to the next hop in BGP... so I still don't get it.

-b



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