Moving providers

[Bab L]

Hi.

We are in the process of moving WAN providers.

This will happen on site to site basis with over 100 sites to complete.

Once each site moves it will still need to communicate with the other site via our DCs.

In order to avoid loops, is tagging the best method or is there a better way of doing it?

Any input will be helpful.

Thank you

[Bab L]

Hi Milan,

thank you so much. I think I'm getting it... slowly.

Question: what are the tags in your example above and what are the deny and permits functions?

[milan.kulik]

Hi Bab,

try to read 

http://www.ciscopress.com/articles/article.asp?p=2273507

or

http://www.cisco.com/c/en/us/support/docs/ip/enhanced-interior-gateway-routing-protocol-eigrp/8606-redist.html

for a better understanding how route tagging and redistribution works.

Which routing protocols are you using for the redistribution in your network?

Best regards,

Milan

[Bab L]

Thanks Milan.

We use eigrp and bgp for external.

[milan.kulik]

Hi,

so one provider is using EIGRP and second provider BGP?

And you need to coinfigure mutual redistribution between EIGRP and BGP?

For BGP you can't use simple tagging as in my example, you would need to use BGP communities instead (or AS prepending using AS numbers).

BR,

Milan

[Bab L]

Hi Milan,

the existing provider we use eigrp for internal and bgp for external.

With the new provider we will keep eigrp for internal and also use bgp for external.

[milan.kulik]

Hi Bab,

so you don't need a true redistribution hopefully.

You just need to check if the providers don't use clashing AS numbers within their BGP networks.

If not, you just need to tag the BGP prefixes received from one provider and advertised to the second provider. You can use either some communities (the providers neeed to accept them) or some AS numbers prepended.

The principle remains the same though:

Just check if the prefix advertised to one provider had not been received (and tagged by you) from him already.

Best regards,

Milan

[Bab L]

Thanks Milan. Appreciated.