[c-nsp] BGP Route Announcement

[Joseph Mays]

Having a problem with changing a bgp route announcement to cogent. We are announcing 216.24.0.0/18 to cogent currently.

router bgp xxxx
no synchronization
bgp router-id xxxx
bgp cluster-id xxxxxxxxxxx
bgp log-neighbor-changes
bgp bestpath compare-routerid
network 216.24.0.0 mask 255.255.192.0
neighbor 38.122.142.5 remote-as 174
neighbor 38.122.142.5 description Cogent A Peer to node router
neighbor 38.122.142.5 send-community
neighbor 38.122.142.5 version 4
neighbor 38.122.142.5 soft-reconfiguration inbound
neighbor 38.122.142.5 distribute-list deny-our-nets in
neighbor 38.122.142.5 distribute-list allow-our-nets out
neighbor 38.122.142.5 route-map cogent-outbound-prefs in
neighbor 38.122.142.5 route-map cogent-out out
no auto-summary

The distribute lists shown also just contained appropriate permit and deny entries for 216.24.0.0 /18

Kind of against my wishes the owner of our company sold several small network blocks we weren't using out of the upper half of the /18. As a result I have to change the bgp broadcast to cogent to broadcast a 216.24.0.0/19 and several smaller blocks we are still using out of the upper half. I assumed if I changed the distribute lists it would change the routes cogent was seeing. So I changed those first --

ip access-list standard allow-our-nets
permit 38.103.73.193
permit 216.24.0.0 0.0.31.255
permit 216.24.35.0 0.0.0.255
permit 216.24.36.0 0.0.3.255
permit 216.24.42.0 0.0.0.255
permit 216.24.48.0 0.0.3.255
permit 216.24.53.0 0.0.0.255
permit 216.24.54.0 0.0.0.255
permit 216.24.56.0 0.0.0.255
permit 216.24.60.0 0.0.1.255
permit 216.24.62.0 0.0.0.255

ip access-list standard deny-our-nets
deny   216.24.35.0 0.0.0.255
deny   216.24.36.0 0.0.3.255
deny   216.24.42.0 0.0.0.255
deny   216.24.48.0 0.0.3.255
deny   216.24.53.0 0.0.0.255
deny   216.24.54.0 0.0.0.255
deny   216.24.56.0 0.0.0.255
deny   216.24.60.0 0.0.1.255
deny   216.24.62.0 0.0.0.255
deny   216.24.0.0 0.0.31.255
permit any

But it didn't change the broadcast cogent was receiving at all. So then I changed the networks statement in bgp config.

router bgp xxxx
no synchronization
bgp router-id xxxx
bgp cluster-id xxxxxxxxxxx
bgp log-neighbor-changes
bgp bestpath compare-routerid
network 216.24.32.0 mask 255.255.224.0
network 216.24.35.0 mask 255.255.255.0
network 216.24.36.0 mask 255.255.252.0
network 216.24.42.0 mask 255.255.255.0
network 216.24.48.0 mask 255.255.252.0
network 216.24.53.0 mask 255.255.255.0
network 216.24.54.0 mask 255.255.255.0
network 216.24.56.0 mask 255.255.255.0
network 216.24.60.0 mask 255.255.254.0
network 216.24.62.0 mask 255.255.255.0
neighbor 38.122.142.5 remote-as 174
neighbor 38.122.142.5 description Cogent A Peer to node router
neighbor 38.122.142.5 send-community
neighbor 38.122.142.5 version 4
neighbor 38.122.142.5 soft-reconfiguration inbound
neighbor 38.122.142.5 distribute-list deny-our-nets in
neighbor 38.122.142.5 distribute-list allow-our-nets out
neighbor 38.122.142.5 route-map cogent-outbound-prefs in
neighbor 38.122.142.5 route-map cogent-out out
no auto-summary

That changed the broadcast cogent was receiving, but not in the expected way. They only route they saw us broadcasting after that was the 216.24.60.0/23 route. Not the first one in the list, not the last one, not the biggest one or the smallest one, but just one route from the middle of the list. I don't get this behavior at all. Cogent cleared and bounced bgp to us, and still received only that one route in the broadcast from us.

Can anyone tell me why I got this behavior, and what am I overlooking in altering our bgp config to broadcast this group of routes? Thank you for your patience with this message.