ebgp advertisement with /22 on ASR1x

[ossniper]

Good day, Please i am still learning BGP, although at work i just acquired a /22 public IP address and ASN. i have configured eBGP and peered with my 2 upstream.

The problem i am having is /22 ip address is not showing on my routing table via network command and also whenever i subnet into /29, i can't reach the internet(e.g 8.8.8.8) unless i configured /24. upstream also not learning the advertised /22 network.

I decide to use ip route 102.200.200.0 255.255.252.0 null0 to inject the /22 into the routing table but still having issue whenever i subnet into /29 or /28, i can't reach the internet, i am using an ASR1002 cisco router, i am confuse and don't know if somethin is wrong somewhere.

Thanks so much

[Harold Ritter]

Hi @ossniper ,

You should be able to advertise your /22 to your upstream provider using the following config:

router bgp <your ASN>

network 102.200.200.0 mask 255.255.252.0

!

ip route 102.200.200.0 255.255.252.0 null0

As far as advertising a /28 or /29 to the Internet, I am afraid it will not be possible as service providers normally filter out prefixes longer than /24 on the Internet.

Regards,

[ossniper]

I'm so grateful for your response.

Yes, i did make use of the network command to advertise the /22 network, but as a static route,

NAS#sh ip route | i 102.200.200.0/22

S 102.200.200.0/22 is directly connected, Null0

My main issue now is, with Upstream filtering /29 or /28, How will be able to subnet my network as i have downstream and other enterprise i will like to give out IP address. is there a way i can resolve this?? 

Thanks.

[Harold Ritter]

Hi @ossniper ,

As I previously mentioned, you should plan to advertise subnets that have at most a /24 prefix length. Anything longer than a /24 will most likely be filtered on the Internet. You could also continue advertising the /22 to your upstream service providers and subnet to /28 or /29 internally in your network. 

Regards,