BGP redistribution

[jlajuarez]

Hi all,

I have a question, on the CISCO IOS command help list, bgp redistribute-internal is listed as dangerous.

Why?

Regards

[Reza Sharifi]

Hi,

Is is dangerous, because that will redistribute IBGP routes into you IGP and this can melt down your router if it is not powerful enough.

You should only redistribute specific routes with route map and not use this command.  Imagine redistributing 250000 Internet routes into your OSPF. (not good)

HTH

Reza

[jlajuarez]

Oh ok...

Thanks for the input...

[Edison Ortiz · Accepted solution]

While redistributing a BGP routing table can be detrimental to an IGP - that's not the reason the command was created as you don't generally redistribute iBGP learned routes from an ISP, those are eBGPs.

By default, you aren't allowed to redistribute iBGP learned routes into an IGP because if you are running an iBGP mesh, all routes must also be on the underlying IGP.

If a router redistributes a iBGP learned into OSPF, another iBGP can potentially redistribute this route back into BGP as OSPF has a lower Administrative distance than iBGP. If this occur, a network loop will impact your network.

Regards,

Edison.

[jlajuarez]

Wow .. ok.. thanks for that very detailed answer... I now get it.