[c-nsp] BGP Advertising - Question re more specific block

[Paul Stewart]

Hi folks.

 

I'd like to know if there's a better way to approach this.

 

We are advertising a specific /22 that belongs to a /18 block via one
specific upstream BGP connection.  The /18 is advertised to all upstreams,
the /22 is only advertised to one upstream as a method of influencing
traffic via that carrier (knowing that if that particular carrier went down,
the less specific subnet will still be reachable via the other providers).
Prepending is very ugly for this situation FYI.

 

We use BGP communities to identify upstream and downstream BGP connections
along with our own netblocks.

 

First I built a route-map that I could use inside the BGP network statement:

 

route-map blahblah-routes-providerx permit 1000

 set community 11666:6001 

 

Then created the network statement:

 

network xx.xx.xx.0 mask 255.255.252.0 route-map blahblah-routes-providerx

 

Created a new IP community-list that includes previous communities plus this
one new specific community (11666:6001):

 

ip community-list 101 permit 11666:4000

ip community-list 101 permit 11666:5000

ip community-list 101 permit 11666:6001

 

And, updated the route-map towards this upstream as applicable:

 

route-map outbound-tsystems permit 10

 match community 101

 

 

My question - is there a better way to configure this?  This is working just
fine for our needs but there's a lot of steps and we're going to have to add
more into this in future so rather do as simple a config as possible ;)

 

Thanks,

 

Paul